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Speedy's TRF801XT Build Thread

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About a year ago I dipped my toe into the world of 1/8 scale buggies when I bought an OFNA (Hong Nor) NEXX8. At that time I was looking at the TRF801X buggy and the TRF801XT truggy in the scratch 'n' dent section of Tamiya USA's site, but I stayed away from these models for a few reasons including cost ($249 for the buggy, $179 for the truggy), the need to create or source an e-conversion kit (another $100), and a perception these models were phasing out quickly -- I wanted some longer term factory support. The NEXX8 fit the bill as my first 1/8 scale buggy since it was already set up for electric and came with everything needed in the box, including some tires and wheels. The cost was only around $210, and then I spent another $200 on electronics and batteries from Hobbyking, and another $70 to do some upgrades including a better motor mount and rear universal shafts. My inspection/build thread on the NEXX8 can be found here: http://www.tamiyaclub.com/forum/index.php?showtopic=68439&hl=nexx8

Out of all my models, the NEXX8 has been the one I've played with the most over the past year. I love going full throttle down my driveway and seeing sparks as the chassis slaps the asphalt street. It's amazing to stand in the street and have it fly by at 45 mph. It chews through grass, gravel, and dirt like you wouldn't believe. It's sent gravel flying up to 30 feet away with the squeeze of a throttle. Jumps are not a problem; the large bore shocks do a great job of soaking up impacts. I've really come to appreciate the center differential and how tunable the vehicle is with different oil weights in all three diffs. The vehicle has been 100% robust and shows no signs of wearing down after all the hard driving it has seen.

I'm glad I bought the NEXX8; it's been a great buggy because it got me into an e-buggy with minimal fuss, and it gave me a chance to experiment and learn a little bit about tuning 1/8 scale. Probably the two biggest lessons I learned from this vehicle include using a heavier center diff oil for on-road driving, and don't always go for a faster motor. While the diffs were set up pretty well for dirt and other loose surfaces, in high grip situations like asphalt I found the center diff would send a lot of power to the front axle, and the front tires would spin and wear down quickly as most of the weight was pitched to the rear of the buggy. Thickening the center diff oil made a big difference in how well power could be transferred to the rear for better launches. As far as the motor is concerned, I have been running a 2650kV motor with 4S LiPo packs, and the speed is great. I did find the motor would run hotter than I liked, and it was not possible to gear much below the stock 13T pinion. It would be better to run a 2100kV or 1900kV motor instead to keep the temperatures more under control and provide some room for running larger pinions if needed.

This past Thanksgiving holiday, Tamiya USA advertised "Black Friday" specials on their site. Among the specials, the TRF801X buggy was available for $179 (later $199), and the TRF801XT truggy was available for $99 -- basically about $80 off the scratch 'n' dent prices seen earlier in the year. After the fun I had with the NEXX8 and some of the lessons I learned, I decided it was time to get one of these TRFs and try doing an electric conversion on it. Since I already have an e-buggy, I wanted to try a truggy next since it has a longer wheelbase, wider track width, and larger tires. I just wanted a new big toy to bash like crazy and not feel guilty about it. There's no way I'd tear up a $900 truggy, but when it's available for $99, I'm a little more willing to hack and bash it.

Fortunately for me, there was already a build and review of the TRF801XT on Oople (http://www.oople.com/rc/photos/review-801xt/), as well as a 100+ page thread on RCTech (http://www.rctech.net/forum/nitro-off-road/235139-tamiya-trf801xt.html). There are also a few companies offering e-conversions for the TRF801XT, including RC Product Designs (http://rcproductdesigns.com/index.php?main_page=product_info&cPath=1_89&products_id=326) and RC Monster (https://www.rc-monster.com/forum/showthread.php?t=31322). There's enough information out there and enough lessons learned by other people that I don't feel like $99 is going to be a big risk.

My goals for this build thread include:

- Share the build process for an 1/8 scale truggy so others can see for themselves the differences between 1/10 scale and 1/8 scale.

- Highlight some good practices and lessons learned by other people as well as myself, incorporating this information in the build process.

- Keep it casual; have some fun; maybe entertain a few of you along the way.

- End up with a truck I'm happy to show off and drive.

Without further introduction...

So I ordered a TRF801XT around Thanksgiving time. Unfortunately, I had to go away on business for three weeks after Thanksgiving, so I wasn't able to open the box and check it all out for myself until earlier this week. I also wasn't able to start any new projects until I installed some shelving in my man cave (see the "So, What Have You Done Today?" thread for a pic). Finally I was able to pull the kit out of the shipping box today and give it a look.

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It's pretty amazing, actually. For $99 the box is completely intact; I don't see any real defects to speak of. The sides of the box show some of the cool features of the kit:

- Straight line drivetrain

- Big bore dampers

- Spiral cut ring and pinion gears

- Machined aluminum steering knuckles and shock towers

- Carbon fiber upper decks

- Sealed radio box

- Full ball bearings

- Turnbuckles

- Lock nut captured hinge pins

- Universal joint shafts

- 17mm wheel hubs

- Front and rear stabilizer bars

- 7075 aluminum chassis

- Chassis side guards

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There's no way this is a $99 kit. To me this is Tamiya's attempt to move inventory quickly and shut down this product line. Or, this is their attempt to seed the market and generate some interest. I don't know, I don't care -- I'm in regardless of what they do with this product line!

Opening the box reveals a few large bags stuffed with parts, a wing, and a body.

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Here's a better view of what's in the box.

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Starting at the top left corner, and going left-to-right, top-to-bottom:

- A bag of suspension arms, hubs, diff mounts, hinge pin blocks, and turnbuckle ends

- A bag of diff cases, radio box, and damper pistons/spring retainers

- The truck body

- A bag with wing mounts and bumpers

- A bag with chassis side guards

- The aluminum chassis

- A rear wing

- Instructions

- A huge bag of metal parts

- Decals

The bag of metal parts is wonderful; it has fluids, thread lock, springs, lots of blue anodized parts, universal shafts, etc. etc. There's a lot of money in this bag alone.

I have to say, the included truck body is a bit of a disappointment. It's narrow with ugly bumps on the bottom to fit the chassis guards on the chassis. I understand the practical reasons for this; it seals the body to the chassis pretty effectively, but I just don't like how it looks.

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I'm thinking of replacing the stock body with a Pro-Line Bulldog body for the Mugen MBX6T. The sides are flatter, and it's a cab-forward design more like a real truck.

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Notice anything interesting about these instructions? They're printed only in English!

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More to come soon...

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Ack! Seeing the directions makes me second guess if I want one of these or not. Even the diff build looks like a hoot! Even if I don't end up getting one, this will be a fun thread to follow! Good luck with the electric conversion!

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Sure looks like an awesome buggy you got there. I'd never heard of the other one you mentioned but that sounds awesome too, you didn't mention what kind of electronics it was running to be so much fun? I just have a lowly Baja Champ to keep my occupied for now!

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After I posted last night, I went through all the reference sources I could find to collect as many build tips and fixes as possible. For the build I'm working on, here are the key areas that need some attention. I've left the nitro-specific thoughts out as they don't apply to a brushless conversion. In no specific order:

- The original front suspension arms are a weak point with this kit. Apparently they are too brittle as molded in the factory. Tamiya later released a "performance package" update with softer front arms and shorter UJ axles, but when using the original arms it's best to boil them in water for about 10-20 minutes to soften them and increase their durability.

- Front suspension droop was tagged as a possible area of improvement, especially for very rough tracks. In the RCTech thread a few people experimented with running the 801X buggy rear damper stay at the front of an 801XT truggy along with longer dampers. In the David Jun build tip article, he suggested grinding some of the front down stops to let the arms drop a little more. This doesn't seem like a critical mod as it depends on track conditions. Some people reported they like the suspension as it was designed for smoother tracks.

- There are several suggestions for improving the diffs. Pre-thread the diff cases, back out the screws, and use fine sand paper to remove the high spots to provide a better gasket sealing surface. Soak the diff O-rings in brake cleaner a little to make them swell some and seal better. Also pre-lube the O-rings with diff oil before installation to reduce operating friction. Apply diff oil to the main gasket so it forms a better seal between the diff case and ring gear. Add grease to the channel cut into the outdrives to reduce wear between the outdrives and diff case/ring gear.

- Gear mesh and lubrication should get some special attention. Use two shims by the ring gear to get a tighter mesh between the pinion and ring gears. Attach the UJ center shafts to the pinions before closing up the diff housings to check/set pinion play. Less play is better than more play, like 0.1 to 0.2 mm instead of 0.5 to 1 mm. This will help save the gear teeth. Use synthetic lube, like Mobil 1 grease, on the pinion and ring gears. Regularly check lash and mesh and shim as necessary, like on any 1/8 scale vehicle.

- Apparently some people have broken the collars that go around diff housings; one option is to buy the hop-up collars from Tamiya. Another option is to use a M4 nut as a spacer, which will help prevent the stock cast collar from fracturing. I haven't seen any pictures of this mod, so I'm hoping this becomes more obvious as part of the build process.

- Cross pins on all UJ shafts/axles, as well as cross pins in the wheel hexes, have been a problem. Even with the grub screws tightened and thread locked in place, the cross pins have a tendency to wander out and damage other parts as a result. The fix is to grind small flats in all cross pins so they are captured against the grub screws better.

- The dampers have their own set of issues as well. The shock bladders are apparently leaky, and replacing them with Losi 5430 bladders fixes them. The screw on top of the damper piston tends to loosen, which lets the shaft come out too far and then damage the lower damper cap. Using thread lock on the piston screws, and allowing them to cure before filling with oil, fixes this issue. The lower damper caps are susceptible to loosening; using a little bit of thread lock on the lower caps fixes this issue. According the David Jun, the front shocks should be filled and closed with the shafts fully extended to get proper rebound. The rear shocks should be filled and closed with the shafts pushed in 10 mm, again for proper rebound. The kit damper oil, 400 cst, is a little soft -- 45 wt / 600 cst seems more appropriate.

- Some general comments apply as well. Degrease all of the aluminum parts, especially the threaded holes, before installation. Thread lock will not work well if there is any residual oil from machining operations. Use grease on some of the longer screws, especially the longer 25 mm bulkhead screws, to avoid stripping the hex heads. A little bit of grease, like ball diff grease, will help these fasteners thread more easily into the plastic.

- A few upgrades might be worth considering. For the diff collar issue, there is a hop-up part that is stronger and also adds some blue bling to the chassis. For more steering, change out the front C-hubs and steering knuckles for the 801X buggy parts.

Based on reading the RCTech thread, the Tamiya USA build tip article, and looking at the RC Universe thread, this seems to be the general set of suggestions and collective knowledge the 'net has to offer. Again, I'm not including a few nitro-specific points as I'm working on a brushless conversion for this build. Building a TRF801XT is going to require some extra care and preparation to get it right the first time.

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Somehow my RC addiction has been gravitating toward truggy too, and will land there if I can't resist it.

Have fun with this, Paul. This thread will be killer informative, I'm sure, by the time you've got your truggy built and dialed in.

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Thanks all!

Today I went to my local hobby shop, a dollar discount store, and an auto parts store to pick up some supplies for this build.

At the dollar store I bought a cooking pot to boil the front suspension arms. My wife and I both agreed we weren't going to risk any of the cookware we normally eat from.

At the auto parts store I bought some brake cleaner (for degreasing metal parts and swelling the diff O-rings), some 1000 grit and 2000 grit sandpaper (for finishing the gasket surface of the diff cases), and some Mobil 1 synthetic grease for the pinion and ring gears.

At the local hobby shop I picked up some Losi 5430 shock bladders, Associated 45 wt damper oil, and some Associated 10k and 20k diff oils. Everything I read suggested roughly 45 wt is a good starting point, and looking at a few setup sheets for high-bite conditions, I'm going to start with 10-20-5 (10k front, 20k center, 5k rear) to get good power transfer, good on-power steering, and hopefully a stable rear end.

Time to spread out some parts and get into the build...

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First up is bag A, which has a lot of very nice metal parts. I also clipped and organized most of the needed plastic parts; combined with bag A, this covers steps 1-7 in the manual. The first set of instructions is building the rear end of the buggy, plus an extra diff for the front later. All of the plastic parts trees are marked >PA-GF<, meaning glass filled polyamide, except for the chassis guards and radio box. The chassis guards and radio box are marked >PA<, meaning polyamide but without the glass reinforcement fibers. This probably makes sense when you consider how much bashing the guards will take.

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Right away I wanted to try boiling the front suspension arms; I've never done this to any plastics before, so this was an experiment to see if it really makes a difference or not. I was nervous about melting the plastic to a hot spot in the pot, so I kept stirring the arms while the water was boiling. The process I used was:

- Fill the pot about 2/3 with tap water.

- Place both arms in the pot of water.

- Heat the pot of water and arms on a stove burner, maybe 3/4 heat. Stir the arms while the pot temperature continues to climb.

- Once the water achieves a medium boil, back off the stove burner to 1/2 heat and continue stirring.

- Set a timer for 15 minutes; stir until the timer goes off.

- Shut off the burner and move the pot of water and arms to a cold burner immediately.

- Allow everything to cool off for an hour, then remove and dry the arms.

Subjectively, the boiled arms feel just a little softer than a new spare set of arms I have. I can flex the boiled arms just a little farther with about the same force applied to them. Will it make a difference? I guess we'll find out when I take the truck for a drive...

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Normally I save the wheels and tires for last in a chassis build, but tonight I broke with convention and prepped/glued the tires to the wheels right away. Why? They're huge, that's why! I've never had tires and wheels this big before, so it's a real novelty to place them next to some existing models and start to imagine just how large this truggy is going to be in the end...

Pro-Line Road Rage 3.8s mounted to Pro-Line Desperado wheels... By the way, the tire diameter is the correct size for a 1/8 truggy -- these are not monster truck tires!

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Comparison of a tire/wheel against a typical 1/10 scale buggy...

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Comparison of a tire/wheel against a typical 1/8 scale buggy...

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This truggy will be huge!

Anyhow, I'll start working on steps 1-7 tomorrow. It's starting to get late here.

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Seeing that all sprawled out on the build table looks like pure RC bliss!! The only thing missing was a good cold beer :) That sure does look like a lot of fun!

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Time to get started with the actual build. First up, the front and rear differentials...

Preassembling the diffs to force the plastic diff cases to flow a little...

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Look closely at the screw holes, and you'll see small ridges of material caused by threading the screws into the part. This happens with all plastic parts like this. These ridges cause the metal ring gear to not completely seat against the rest of the diff case, so it's up to the gasket to fill the void and prevent leaking. Rather than trust the gasket, I prefer to sand these ridge down so the two surfaces are as close to each as possible. This makes the gasket more effective.

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I sanded the diff cases with 1000 grit sandpaper, working in a circular motion and rotating the part in my hand regularly. The idea is to apply as even pressure as possible so the excess plastic is removed and the ring gear still turns true when assembled later.

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Result... Note I did not remove a lot of material, just most of what was protruding above the screw holes.

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Prepping the O-rings. Initially I soaked the O-rings in CRC brake cleaner for five minutes to make them swell just a little bit, then I lubricated them with diff oil prior to installation in the diff case and ring gear.

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Prepping the outdrives. I smeared anti-wear grease in the small grooves, and left a little extra on the shaft surface.

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Installing the bearings, outdrives, and cross pins. The bearings are 1680 throughout.

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The internal gears are really high quality; they simply lay on top of the cross pins and are separated by the spider gears and cross shafts.

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Spider gears and cross shafts. These are the same high quality as the gears on the outdrives. Note the shims. It's easiest to assemble these parts outside the diff, then drop the whole subassembly into the diff in one shot.

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Filling the diff with fluid. Don't forget the grub screw that goes in the side of the diff case first! I filled these diffs with oil part way first, then spun the gears a little to force air up. Once the oil level settled again, I filled some more, spun the gears some more, watched the level, and repeated until the oil just covered the cross shafts. Since I'm running street tires on asphalt initially, I'm setting up the front with 10k and the rear with 5k.

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Installing the second outdrive gear, and installing the gasket. The gasket has already been wetted with diff oil.

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Two complete diffs... I used a pencil to write the oil weight on each so I don't mix them up later.

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The next steps involve building the gear cases, rear bulkhead, and attaching the center CV shaft. I spent some time test fitting all the parts and found a few things:

- One of the diffs only needed one shim on the ring gear to get a decent mesh; the other diff needed two shims. EDIT: Ultimately, both diffs needed two shims near the ring gear. The diff housings have to be fully closed and secured to judge the mesh better; while the rear was in good shape, the front had to be opened up to add another shim.

- Since the pinion and ring gear have a helical cut to them, any rotation causes a thrust force on the pinion shaft. Having a lot of lateral movement due to thrust forces changes the mesh, which is a bad thing for teeth life.

- Good goals include decent static mesh, no binding while spinning, and minimizing pinion movement due to thrust forces.

Test fitting the rear center CV shaft on the pinion gear, I found a good millimeter or so of side movement. To reduce this, I ground part of the pinion shaft so that the grub screw would bite into the pinion shaft better. With this arrangement I was able to get the play down to almost no thrust movement, which means the gear mesh should stay the same under acceleration or braking loads.

All the CV shafts in this kit have to be disassembled so the cross pins can have flats ground into them. This prevents the pin from slipping out the side of the joint and damaging parts.

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Diff, pinion, and CV shaft all put back together and installed. Mesh is good, no binding, and minimal thrust movement now. I lubed the pinion and ring gear with Mobil 1 synthetic grease.

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Upper diff housing installed. The rear of the housing is held in place with just one screw; the front of the housing is secured with a collar that slips over it. It doesn't look that beefy, but once it gets surrounded by other parts everything interlocks and it's very solid.

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There were a few comments by other people that they stripped the longer 25 mm stainless steel screws while assembling the kit; it was suggested that greasing the screws would make them go in more easily. I used some ball diff grease on four button head and countersunk stainless screws, and they went right into the bulkhead parts with no problems at all.

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Here you can see the bulkhead surrounding the diff housing. The front and rear halves clamp the top and bottom halves of the diff housing together. The silver stainless screws were lubed and went right in. The black button head screws for the collar set the angle of the diff relative to the chassis plate; this means the same parts work at both the front and the rear of the buggy while maintaining a straight drivetrain. The rear hinge pin block is made of plastic and sets 2.5 degrees of toe. There are other blocks included on the same parts tree to set 2.0, 2.5, and 3.0 degrees of rear toe.

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Finally some bling! The front hinge pin block is made of aluminum; inserts are used to set the anti-squat.

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Building up some rear subassemblies. The wing mounts have some blue aluminum cross pins. The wing is adjustable for both height and angle. The rear damper stay is a machined piece of aluminum; body post mounts and damper mounts attach to it.

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Now it's starting to look like something!

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Attaching the rear arms and turnbuckles. The turnbuckles are huge! They're adjusted with a 6 mm wrench. There are no ball connectors or ball cups; instead, every joint is fully captured. The bottom arms are held in place with hinge pin screws and locking nuts; inserts go into the front block. This is nicer than the NEXX8 I have, which uses e-clips on the lower suspension arms.

By the way, check out the two Tamiya wrenches side by side. The one on the right is the usual cross wrench supplied in most kits; the one on the left is what Tamiya supplies with these TRF801 kits. "That's not a wrench... Now THIS is a wrench..." (Flashing back to the Crocodile Dundee movies...)

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Prepping a few more cross pins for CV shafts and 17 mm hex hubs. Again, this is to make sure they don't slide out sideways and damage the joint or hub.

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Rear assembly complete. It's hard to believe I just burned six hours on this. Then again, there were a lot of little details and modifications to make during this part of the build...

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Next up, bag B...

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I think you're looking for "helical cut" for the ring and pinion 1:1 car/truck R&P's are done the same way..

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I agree helical cut is a good thing; it provides more contact area between teeth. That said, any lateral movement of the bevel pinion gear is bad because it alters the mesh. Minimizing the mesh change under load is a good goal to shoot for.

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Yes the back lash is important which is why it's (helical cut gears) probably not done to often in the RC level.. another upside to helical cut gears is they handle more power than straight cut..

Does the kit come with shims/spacers to keep the R&P tight?

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Q&A time:

Sure looks like an awesome buggy you got there. I'd never heard of the other one you mentioned but that sounds awesome too, you didn't mention what kind of electronics it was running to be so much fun? I just have a lowly Baja Champ to keep my occupied for now!

Here are the electronics I have in my NEXX8:

- Turnigy nano-tech 2S 6000mAh 65C-130C LiPo batteries: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=24196

- Turnigy Trackstar 120A-760A sensorless brushless ESC: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26503

- Turnigy Trackstar 2650kV sensorless brushless motor: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19682

- Turnigy 1258TG titanium gear servo: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=30872

- Futaba R2004GF receiver (used with 3PL transmitter): http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZZD1&P=ML

For this truggy I want to try a pair of shorty packs to balance the weight a little better from side to side. I also want to try a 2100kV motor to keep the heat under control a little better and to gain some gearing options.

Yes the back lash is important which is why it's (helical cut gears) probably not done to often in the RC level.. another upside to helical cut gears is they handle more power than straight cut..

Does the kit come with shims/spacers to keep the R&P tight?

The kit includes shims for the ring gear and internal spider gears, but there are no shims for the pinion. Given the angle of the teeth between the ring and pinion, shimming the ring looks much more important.

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All right, here's bag B sprawled out along with associated plastics. Bag A was all about the rear end of the buggy (with an extra diff for the front); bag B is all about the front end of the buggy (with an extra sway bar set for the rear).

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I worked a little smarter this time around and degreased all the metal parts right away in a single batch. I also broke down the CV shafts and axles, and grabbed the hex drive pins, and cut slots in all the pins at the same time. I also cut a recessed flat in the diff pinion shaft right away. This saved me a few trips up and down the stairs between the cave and garage, and saved me some setup time. With the front arms already boiled, the CV shafts rebuilt, and the diff already (mostly) finished from bag A, this part of the build went much more quickly. I think I finished bag B in about 3 hours instead of the 6 hours I burned on bag A.

Originally I had a single shim installed on the front ring gear, but closing the housings and temporarily adding the collar made me think I could use another shim, so I did that right away. I also had cut a recessed flat in the pinion gear shaft, just like the first one, so I put a little time into checking lateral movement again. It all checked out ok, so I lubed the gears with the same Mobil 1 grease.

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All closed up, just like the rear diff...

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Adding the bulkheads and hinge pin mounts... This is very similar to the rear diff, except the placement of the aluminum mount and the plastic mount are reversed relative to the center CV shaft. The net result is the aluminum is always facing forward in the chassis. Also, for the front diff the collar is now secured to the upper hole in the bulkhead to compensate for the bend in the front of the chassis plate.

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Damper stay and body post mounts added... Like the rear diff, I greased the stainless steel button head screws to promote easy threading.

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Front arms and camber links added. This is pretty much the same design as the rear with captured joints, threaded hinge pins, lock nuts, and inserts.

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I think these front steering knuckles are works of art. They look machined, not cast; the edges are very sharp. The bearings slip inside the knuckles perfectly. There's no slop whatsoever between the knuckles and the C-hubs in any direction.

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Hubs, knuckles, and shafts installed... Again, the hinge pins are captured with lock nuts.

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The last part of bag B is building the sway bars. Both the front and rear bars are "medium" strength (yellow) in the kit. The ends of the bars are even with the ends of the connectors, although there is the option to move the connector further in to fine tune the sway bar action.

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Sway bars installed, both front and rear...

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So, no real surprises in bag B. The build went a little more quickly based on experience with bag A. Next up is bag C, where the center diff, steering rack, and chassis are prepared. Then the front and rear assemblies are installed. More to come...

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Yes, it definitely is a lot of kit...

A lot of pieces started coming together today and I feel like I'm close to having a chassis now. Bag C is all about the center chassis, steering, and securing the front and rear assemblies to the chassis... In addition to buying the kit, I also bought the blue aluminum center braces for $17 to replace the kit plastic parts.

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Since I knew bag D (dampers) was following this bag, and I knew the screws holding the pistons needed thread lock, I broke into bag D early and assembled the shafts, pistons, and screws to give the thread lock time to dry before using them with damper oil. There is actually a right way and a wrong way to install these pistons on the shafts; if done correctly, there is a recessed feature in the shaft that gets hidden in the piston. Done incorrectly, and the piston rides on top of the recessed shaft feature, and the split washers have almost no material to grab. The manual doesn't call this out, so special attention has to be paid here.

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Back to bag C... The first two steps are for installing the chassis guards, various posts, the center diff mounts, and the nitro engine mount plates. Everything was straightforward except the chassis guards, surprisingly. The plastic parts have hexes molded into them, so in theory they should hold the lock nuts while rotating the screws from the bottom of the chassis. This actually didn't work; instead, the plastic was so soft that the nuts would rotate in the guard hexes (due to the nylon in the nut resisting the screw more than the guard resisting the nut). To make it even worse, the plastic guards where so thick it was not possible to get a wrench on the nuts and hold them while screwing from the bottom. Eventually I solved this problem by pre-threading every lock nut on a screw first, then installing them upside down in guards. Pre-threading the nuts guaranteed the screw thread would engage the metal part of the nut properly, and installing them upside down actually provided a little bit of the nut body to get a wrench on them. In the end the solution worked, but it took some extra time to figure this out.

I didn't have to install the engine mount plates, but they're nice blue aluminum, so in they go for now...

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The center diff went together pretty much like the front and rear diffs.

- Pre-threaded the diff case and sanded the gasket surface.

- Soaked the O-rings in brake cleaner for a few minutes, then lubed them with 20k diff oil.

- Lubricated the outdrives with anti-wear grease.

- Installed the bearings, outdrives, and O-rings, slid in the cross pins, installed the large bevel gears.

- Installed the grub screw in the diff case.

- Prepped the cross shafts, spider gears, and shims; dropped into diff case.

- Filled with 20k diff oil to the top of the cross pins; rotated gears to work out air bubbles and get a true reading on the oil level.

- Dropped in the other large bevel gear.

- Lubricated the diff gasket with 20k oil, placed on top of the diff case.

- Dropped the spur gear on top, and screwed it all together.

Instead of a helical cut ring gear, the center diff has a straight cut spur gear (50T).

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Here's the center diff installed. The upper center diff mounts, carbon fiber plate, and screws make this a really solid attachment. There's no give or flex anywhere.

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Here are quite a few unused disc brake parts. In a nitro setup these would definitely be installed since the engine and clutch provide no braking capability whatsoever. In an e-conversion, the electric motor provides braking just like in a 1/10 electric setup. I did think about installing the brakes, running a second servo, and programming the speed control be forward-only just like a nitro engine. The reason for doing this is the brake bias can be adjusted for the front and rear independently, which is a very useful tuning aid. Since I don't know how much room I need for the e-conversion yet, I'm leaving these parts off for now. The idea of actually using the brakes, though, is still in the back of my head... Just a side note -- Mugen calipers and pads will fit on the TRF801XT.

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Here are the front and rear assemblies attached to the chassis now.. The rear brace upgrade is installed, but the front one is installed with the steering later. It's starting to look like an actual chassis!

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Bottom side of the chassis... The front and rear key into the chassis plate nicely. In the rear you can see the aluminum hinge pin mount peeking through the chassis; the rear plastic block also surrounds the rear of the chassis. The front is keyed with two plastic bumps, the front bumper, and the aluminum hinge pin mount. Everything feels really solid.

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Here's the steering assembly. The servo saver is built into one of the posts; just a linkage and regular arm attach to the servo. The strength of the servo saver is set by how much the upper collar is threaded onto the post; this compresses a spring which in turn compresses two V-shaped half posts together. Note the bearings in the steering posts. I will say getting the collar threaded the first few turns while compressing the spring was a little challenging; it takes two hands alternating between applying pressure and rotating the collar to do it without cross-threading the collar on the post.

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Here's the steering installed, along with the front brace. The posts and bearings slip over the posts already mounted to the chassis plate. Turnbuckles are installed to connect the steering bridge to the knuckles. A carbon fiber plate reinforces the steering against the front bulkhead, and a blue aluminum brace stiffens the front of the chassis plate.

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That pretty much completes bag C.

More to come soon...

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I wish TamiyaUSA's online store was open! I want one of these to make a buggy out of! NIce build man! Do you have the hop up part numbers you bought besides the kit?

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I wish TamiyaUSA's online store was open! I want one of these to make a buggy out of! NIce build man! Do you have the hop up part numbers you bought besides the kit?

If you want a 1/8 buggy, then Tamiya USA has #84067/84067SD TRF801X buggies for $199 right now. Starting with a 49497/49497SD TRF801XT truggy and then converting it into a buggy would be more expensive than just going for the buggy kit itself, as there are quite a few differences between the two...

Here's a complete list of everything I've bought so far (except electronics):

- Tamiya 49497 TRF801XT truggy kit ($99.99 from Tamiya USA)

- Tamiya 84037 TRF801XT aluminum braces ($17.12 from Tamiya USA)

- Losi 5430 shock bladders ($5 from local hobby store)

- Proline 2733-03 Desperado 3.8 inch Black 1/2 Offset 17 mm Wheels Front/Rear ($13.79/pair before Tower discount)

- Proline 1177-00 Road Rage 3.8 inch Street Truck Tire Front/Rear ($25.99/pair before Tower discount)

Electronics I have:

- Turnigy Trackstar 120A Brushless Short Course Truck ESC ($49.99 at Hobbyking)

- Turnigy Trackstar 1/8 Sensored Brushless Motor 2100kV ($56.42 at Hobbyking)

- Turnigy 1258TG Digital Titanium Gear Servo 57g/13.5kg/.10 sec ($33.52 at Hobbyking)

- I already have a radio and receivers, and I already have some 6000 mAh, 65C-130C, 2S LiPo batteries that I wire in series to get 4S.

I'm about to buy:

- Proline 3318-60 Bulldog Clear Body MBX6T ($24.99 before Tower discount)

I'll have to source an e-conversion from RC Product Designs or RC Monster, either case it will be about $100.

Grand total will be about $475 when I'm done.

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Onwards with bag D to build the dampers... Look at the difference between the Tamiya bladders and the Losi bladders!

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Here are the lower guides and O-rings for the dampers... I have to give some credit to TA-Mark here; let me explain. Typically with Tamiya instructions they show installing the guides and O-rings into the damper body first, then sliding the shaft through the shock body. It's good practice to lube the shaft before doing this as it helps reduce the chance of damaging an O-ring. TA-Mark rightly pointed out that it's better to install the guides and O-rings on the shaft first, then slide them up into the bottom of the damper body. This greatly reduces the chance of cutting an O-ring because there are no compressive forces on the outside of the O-ring. In this build, I wetted all the guides and O-rings with damper oil first, slid them on the shaft, then pushed everything into the damper body. I like his method and just want to credit his thought here.

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Four damper bodies stuffed with guides, O-rings, shafts, and pistons... I opted not to put thread lock on the lower caps; instead, I used a small adjustable wrench to torque these caps a little more than I could do by hand.

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Threaded collars for the damper bodies... There are O-rings that fit inside these collars. I lubed these with damper oil as well, because it makes it easier to thread the collars up the bodies. Plain rubber will tend to grab at the damper body threads and make adjustments more difficult.

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Here's one complete shock. I really love the dust boots typically included in 1/8 scale vehicles! They help to reduce the wear and tear on the damper shafts due to dirt. I also have some Dynamite CV joint boots on order to protect all the CV shafts and axles. Even though I rubbed graphite on all the CV joints and dogbones (to not attract dirt), I want some protection over every joint to really bullet proof the drivetrain. I know Durango offers some boots for axles and damper shafts for their 1/10 scale line, but it doesn't seem that common with 1/10 scale in general...

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And here are four complete shocks... They all feel nice and smooth, and the pairs seem pretty well matched.

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Here are the front dampers installed. This is very straightforward. The upper caps are secured with plastic bushings, washers, and lock nuts. The lower eyelets are secured with cap screws threaded into the suspension arms.

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And here are the rear dampers installed. It's the same installation process as the front ones.

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