Jump to content
SlideWRX

SlideWRX's DT-03 Modification Thread

Recommended Posts

This is my DT-03 Mod thread.  I'll show the modifications that I don't really see others doing, or not that often. Really, whatever I want to show, right? Build/Mod thread!  :)   First off, the car was built stock, with only bearings as an upgrade. 

 

506308581_1IMG_0645_small.thumb.jpg.b9329d97b2188e383fb3f5360923ad7e.jpg

One thing I did right away was grind the drive cups to get more suspension travel.  Tamiya should have tweaked that mold a long time ago. :( Initially I popped these into a drill and spun them against sanding paper.  The gap made it bouncy when sanding though, so it wasn't even.  I went back later and smoothed it out. 220 Grit paper worked fine.  You can see it still rubs a bit on the lower suspension arm in the pics below. There is the clean spot on the lower control arm.

 

605127125_2IMG_0656_small.thumb.jpg.d8fc60e9be434982cfacecf99f2ee586.jpg

Checking the Center of Gravity.  I also tried to balance it on the side to get the height.  I couldn't keep it steady on it's side for a pic, but the yellow/black point is the Cg. I was surprised how high it was!  That is completely above the NiMH battery.  Looking at it, the motor is mostly above the Cg, the ESC & receiver, and the oil filled top half of the shocks.

 

831871171_3IMG_0648_small.thumb.jpg.e281802ecb6b8238afb2df15cff1d61a.jpg

More to come.

 

  • Like 4

Share this post


Link to post
Share on other sites

I have a seek thermal camera, so I looked at the motor after a run. This run was split between asphalt & medium grass running for a pack.  The shell is still on.  1520516158_4IMG_0697_small.thumb.jpg.87ad5f44745346297185d51601397e1f.jpg

Here is the motor close up.  The camera has a manual focus, but it is a bit fidgety.  Still working on getting good quality pics.

1733626356_5IMG_0698_small.thumb.jpg.7edd8c3fa789e4de3346bc88f27f5d8a.jpg

Later on, I did a run mostly in the grass.  It wasn't short grass, and apparently the motor got pretty hot!

1705998095_6IMG_0798_small.thumb.jpg.66d50c8d40b998974dced57d62c9473a.jpg

182F is ~86C.  at one point I saw ~195 on the motor, but didn't get a screenshot. I was worried it got TOO hot, but several runs later, it seems no worse for wear. ESC (below) and battery were ok though.

652823079_7IMG_0799_small.thumb.jpg.d59b23560430099a55fde8f66c8fe431.jpg

  • Like 2

Share this post


Link to post
Share on other sites

At one point, While trying to find a solution to change the open diff into a limited slip, I tried Permatex Anti-Sieze grease.  Chemically, it is virtually identical to Tamiya Anti-Wear grease.  $5 at the auto parts store gets you 20 times more stuff than that tiny Tamiya cupfull. Mine was left over among my tools from... 15? 20 years ago?  Anyway, I used that in my diff.  A LOT. :D At first it was great! Definitely limited slip.  After about four battery packs though, it seemed to have lost a lot of of the limited part - it was back to spinning fairly freely.  I decided to open up the gear case and...

IMG_0765_small.thumb.jpg.2aaf094669f43e13a9d88e9d2b4ad515.jpgIMG_0766_small.thumb.jpg.67580d4a52eaf28669efdb551bf4ad0f.jpg

Aw man, it got out everywhere!  Not just out the screw holes or the edge (I could have sealed those up eventually), but out through the bearing in the center. Ah well, I spent a couple days cleaning that stuff out of my gear case.  It isn't bad stuff - it is basically anti-wear grease, so no real damage done to anything, just a mess.  It is sticky, however, and may have contributed to the hot running a bit.  That stuff managed to get ALL the way through my gear train - all the way to the pinion!  Anyway, back together with just a dab of grease in the right spots, and light oil on the gears, and I am off and running again.  The quest to limit slip will continue another time...

 

  • Like 2

Share this post


Link to post
Share on other sites

Todays post is going to be about Ackermann. For more info on Ackermann, check out the wikipedia article on it.  https://en.wikipedia.org/wiki/Ackermann_steering_geometry There is a basic explanation, and it links to several papers that discuss it in depth for those interested.
Anyway, for some reason, Tamiya at some point switched away from ackermann for *some* of their buggys.  Old 80's buggy like the Frog & Hornet upright steering arms have Ackermann built in.  The DT-01/02/03 series were produced with straight upright arms. I'd say ackermann was originally done to fit steerng uprights to smaller wheels, and they stopped when the wheels got big enough to fit straight arms, except they produced the Astute, TRF201 & DN-01 with angles in the steering arms. Every performance buggy out there WIth 2.2" wheels has Ackermann built into the steering, usually adjustable.

I have decided I want some ackermann in my steering!  It makes me wonder - without it, is the inside wheel fighting the outisde wheel, especially on turn in, and is that partly why the DT-03 handling isn't great?  I picked up part number 54154 - Rc Carbon Reinforced Uprights.  These are for the F103/F104 chassis.  I had some ball connectors that fit after I drilled out the hole to ~3mm.  This upright seems common to a LOT of chassis - it looks identical to those old 80's uprights.

9949f1486630846a3ee5c1609407bf58.jpg.7d51e0552b9e80ec1272cac0a5c8244c.jpgIMG_0730_small.jpg.67bfe43c323a89745e3deed519df132e.jpg

The uprights fit exactly like the original part.  In order to get the steering throw that I had with straight arms, I had to do a little grinding - on the arm, and the upright too.  That is partly why I grabbed the reinforced uprights.  We'll see if it holds up.  If not, oh darn, time for an upgrade! :D The stock steering arms have just enough adjustment to go in far enough, about 42-43mm.

IMG_0733_small.thumb.jpg.55b96baf6a3882f76c723038e55f589a.jpg

I added in a 0.5mm shim, on the top side, to take up the vertical slack in the upright, that was also there on the stock uprights too. It's hard to see in there; it's black like the rest of it. 

IMG_0859_1_small.thumb.jpg.c50a0de6104209e71248dbe90adb10db.jpg

  • Thanks 1

Share this post


Link to post
Share on other sites

Well, another thing that bugged me about this vehicle is the front shock towers.  Plenty strong/sturdy, yeah, but ugly and it requires the front end of the shell to be cut into a little flap.  Maybe someday I'll redesign the shock towers to look good and be strong and not mess with the body.  For now, I'm cutting the center brace off. 

IMG_0848_small.thumb.jpg.85ba1945f8d5c2a6e24d9046604e1294.jpg

IMG_0844_small.thumb.jpg.e623f93191e370858e8702ea2151f64d.jpg

To add some support, I added these links to take some of the force from the shocks.  They mount to the holes used for the body mounts for the Aqroshot.  The shock top mount gets a ball collar, and various ball connectors and screws are put together to tie the whole thing together.  you can see the ball head connectors at the top are bent a bit when installed.  I may trim them to straighten them out, and I need to trim the leftover thread as well.  I'm using the original front stays for now, but I have the fiber reinforced ones ready to go in if these bend/break.

IMG_0718_small.jpg.23195cc52556ffb58b2ce067e5a1a53c.jpgIMG_0727_small.thumb.jpg.e1f629cf6edccd53ce0c1025e27e20e6.jpg

 

IMG_0846_small.thumb.jpg.f31846fefa32e6be1bdaf83a2e3b4bbf.jpg

 

  • Like 2

Share this post


Link to post
Share on other sites

Limited Slip - Again
Oh, look at that!  Upgrades!  New drive shafts, a turnbuckle kit, and some new shafts for the front suspension!

IMG_0902_try2.jpg.0e3047a8950f7ae7fab498a8f9daa2f4.jpg
Oh I'll go through it all in excruitiating detai- What, no.  You've seen that all before, a lot I think.  Hey, gosh, while the rear suspension is apart, I might as well open the diff! :D
One thing that bothered me while I was putting the diff back together last time was that the planetary/pinion gears had a lot of slop in/out, sliding along the guide pin.  That means the gears aren't meshing as tightly as they could.  
Anyway, you can see from this pick I was able to wedge the 1.5mm hex head in the space between a gear and the guide slot.  Yes, that is messy in there.  It is what is left of the anti-wear grease I tried last time for a limited slip effect.  It isn't hurting anything, so I didn't worry about scrubbing it clean.  

IMG_0905_small.thumb.jpg.9079e4e2566754324e1f1337406971c3.jpg

I recently picked up a variety pack of 3mm shims. I started with the 0.5mm shim on the outside/back of each planetary.  It barely fit, but the Sun/Ring gear didn't sit right. Next was a 0.13 & 0.25mm shim together (0.38mm),  and the planetary still didn't *quite* fit.  I tried 0.25mm at each end of each guide pin, and the Ring gear fit tightly.  I plugged in the cup joints for the driveshaft in and gave it a spin.  Notchy!  Turning gave a bit of resistance, a bump-bump-bump feel as I turned it.  I checked using just a 0.13mm shim and got just a hint of notchiness, with very little resistance. I put the 0.25mm shims back in and closed it up. I didn't use the shim on the inside.

IMG_0906_small.jpg.9fface172bbf99e0323e41d7c71360af.jpg
That notchy feel probably means the gear mesh is too tight. Realistically, where are they *supposed* to mesh?  Logic says they get flung to the outside while driving, so theoretically that is where Tamiya designed the gear mesh to be perfect.  Right?  Maybe?  We'll see how it goes. $10 total for the gear bag and bevel gear set on Tamiyausa.com, so no worries if it really wears down or breaks.  When the whole car is put back together, the feel at the tires is actually fairly small.  With the standard setup, I can spin a rear tire at it will spin 4+ revolutions before stopping.  With this, it is ~1-1.5 revolutions. The diff still turns; it isn't overpowering the gear train friction/motor drag.

After a couple battery packs it is still notchy.  I purposely drove over some taller grass and pine tree loam that gave me problems.  The grass went really well.  Only when I was driving slow in a couple trouble spots did it get stuck, and that was on fairly worn tires.  new spikes had no problems.  The pine tree loam was pretty good too, but one really soft spot had both rear tires digging holes for themselves.  I think that is still good news for the diff.  I will update after more packs are run through.

 

  • Like 1

Share this post


Link to post
Share on other sites

As for those upgrades, pretty nice.  The rear turn buckles weigh 12 grams vs 25 grams for the original plastic arms, with all the hardware.
The drive shafts weigh 34 grams for the set vs 40 grams for the stock ones.  Plus, it is much smaller in diameter for less rotational inertia. Because the ends are so much smaller (5.7 vs 8.9mm diameter), the shaft is longer (70 vs 58mm).  I think 68mm would work too.  It has the same range of motion my modified stock ones did. One more millimeter of compression, and I think the driveshaft would bind on the drive cups.

IMG_0903_HD_try2.jpg.c531493e48c1a5dd783ab517bf97a33a.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Oh wow, has it been six months since I posted here?!?  Some things have changed; I switched the rear suspension over to DF-03 arms that other members figured out fit the DT-03/2 quite well.  It gives a bit more suspension droop, and the arms have ~3 degrees of toe in, where the stock DT-03 arms seem to have half a degree.  I've been very happy with that setup for a while now.  Here are some pics to show the difference:

IMG_1066_crop_small.jpg.336a312606cde1019dd7f19fafb8e35f.jpg

IMG_1068_crop_small.jpg.2cb7a00194b8eb492dc951f13841bf09.jpg

Here is a thing that has bugged me for a while - the steering!  I think it annoys a lot of DT-03 drivers.  The common thing to do is to add weight at the front, but I think the geometry can be significantly improved as well.  I previously updated the steering arms to ones that will give me ackerman, to reduce the arms fighting each other while turning.  That seemed to help, or at least didn't hurt :D the steering radius was still pretty bad though.  That was the first part.  The second part is trying to fix a couple things - bump steer from the long steering rods, and getting a bit better geometry for the steering.  That is a bit of a challenge, as the DT-03 isn't set up to change the steering system!  I had to hold on this, while I thought out a solution.  A solution has been found, although I wonder what all of you think of it...
I am posting mp4 files, because converting to gif for some reason increase the file size ten-fold.  If it doesn't work, I'll edit it with gifs.  you should be able to right click and loop if you want.

 

ConvertToGIF_2_cropped.mp4

 

 

IMG_1356_crop_small.jpg.68a9b14e97939f9037a13a5433a40f7e.jpg

 

ConvertToGIF_1_cropped.mp4

 

 

The steering arms stay parallel with the suspension arms when compressing, so no bump steer.

  • Like 3

Share this post


Link to post
Share on other sites

Thanks!

The video showing the steering from behind shows a double stacked connection on top of the blue linkage.  The arm on top is going inside to the servo.  It is one link from the servo, to that end of the blue bit on the right that steers the whole thing.  It is the same servo saver as original, with just one connection instead of two.  The arms on the side of the body are to hold the whole thing up from scraping along the bottom of the opening.  They are 3mm threaded rod bent to the right shape.  The blue linkage is from TRF product, that happened to be on sale on the tamiya usa site and was an impulse buy, because I figured it was about the right size for this project.  In hind sight, I think some 3mm threaded rod would have worked too with some different ball connectors.

 

  • Like 2

Share this post


Link to post
Share on other sites

Here are some more pics showing the linkage on the right side, and no linkage on the left.

IMG_1359_crop_resize.jpg.23704088fe5f24942987ef13112b828d.jpgIMG_1357_resized.jpg.7ea0da197066e2106524a0812cb1024b.jpg

  • Like 3

Share this post


Link to post
Share on other sites

Four months passed... 

  I installed a hex conversion I designed myself onto the buggy.  This buggy is running version 1, and my DT-02 Almost Comical Grasshopper is running version 2, and version 3 is what is for sale on shapeways.  Nothing has broken so far, even with a lot of intentional bad driving on my part to see if I could break it.  tumbling end over end, running into things with the wheel, etc.

IMG_1662resize.jpg.a8d9950cc8cd34e78bdc93ec16be4903.jpgIMG_1663resize.jpg.a55cf4703cbc73d28c72ef4cb412a2f1.jpg

Well, I opened up my diff after putting the spacers in previously and everything has been fine.  Those spacers of the planetary gears only added a little bit of stiffness to the diff, so this time I added spacers on the big gears to tighten everything up.  0.2mm on one side and 0.1mm on the other and the diff has tightened up nicely, without compromising the diff assembly.  I got stuck in the deep grass, but both wheels were turning...  Again, we will see how well this holds up in the long run.  6mm spacers fit just perfectly in there, although I bet 5mm or 3mm would work well too.

IMG_1689.jpg.c7278a7bb9097f5a2dd5f877655be651.jpg

 

Share this post


Link to post
Share on other sites

New Spur gear!!!
    Or rather, an old spur gear.  The Stadium Blitzer uses the same style of spur & counter gear molded together.  It has the same 19 tooth counter gear side, but the spur side is only 50 teeth compared to 55 of the DT chassis.  Instead of having a 17 or 19 tooth pinion, 22 or 24 would be the options.  The ratios change from 9.3 & 8.3 overall (17t & 19t) to 6.6 & 6 overall (22t & 24t).  The pics are of a 22 tooth fitment.  There are a couple issues to watch for:
    1. the counter gear is shorter than the DT gear, so instead of having ~12-13mm of contact with the idler gear, it only has 6-7mm contact.  I will run for a while and see if it wears or breaks or anything.  Because of that shortness, I added a 5mm spacer on the shaft to keep the bearings in the right spot and not wandering.
    2. The blitzer gear has a flange on it that forces the pinion fitment tight against the case on the motor side.  I had a heck of a time finding a spot to feed the hex wrench to tighten down the gear.  Eventually I got it though.
I'll  do a before/after top speed run to get some numbers posted.

IMG_1731.jpg.3d6acddf5237fe849f84e9bf22d49a97.jpgIMG_1732.jpg.f68cae8892459b2175ddb15c39a48942.jpg

IMG_1712.jpg.e48bfe3af11eaf29918ce9497e549942.jpgIMG_1715.jpg.046fb41a8e170baca8a9c19ae5aa4f27.jpg

 

Part number is 9335111, $7.50 on TamiyaUSA.com

TY309335111.jpg.70ef2d507ca48225ad0a0be816c0bcd7.jpg

  • Like 4

Share this post


Link to post
Share on other sites
On 3/31/2022 at 9:09 PM, SlideWRX said:

Here are some more pics showing the linkage on the right side, and no linkage on the left.

IMG_1359_crop_resize.jpg.23704088fe5f24942987ef13112b828d.jpgIMG_1357_resized.jpg.7ea0da197066e2106524a0812cb1024b.jpg

Was just searching the net looking for something like this and expecting to find nothing. But here you are having just done it! Amazing. I think I may have a go at copying your linkage idea. Maybe made out of carbon fibre sheet, if I can make that work.

Keen to hear - how do you get on with this mod in practice? And could you tell me what that blue trf part is as well? 

My DT-03 is crying out for more M3 rod 😁

20220116_221059

And now I'm here your spur gear mod has my ears pricked up as well. 

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites
18 hours ago, BuggyDad said:

Was just searching the net looking for something like this and expecting to find nothing. But here you are having just done it! Amazing. I think I may have a go at copying your linkage idea. Maybe made out of carbon fibre sheet, if I can make that work.

Keen to hear - how do you get on with this mod in practice? And could you tell me what that blue trf part is as well? 

My DT-03 is crying out for more M3 rod 😁

20220116_221059

And now I'm here your spur gear mod has my ears pricked up as well. 

MORE ROD!!!! :D 

3454808 is the Tamiya part number.  It is the Steering Bridge for the TB-03 VDS, currently on sale at Tamiyausa.com for ~$14.  I searched online what I could find of steering bridges, and this one looked roughly the right length so I bought one to try out.  In operation, I haven't had any big troubles.  I added a spacer to The 'L' arms (shown below) to flatten out the sweep of the arm to reduce the last bit of bump steer when turned full lock.  I had to trim the servo horn a bit to clear the steering bridge.  I can't get a good pic of that without pulling it all apart, but you can kinda see in the pictures that the blue bridge gets really close to the white servo horn.  When turning it contacts it.  I could lengthen the 'L' arms to push the bridge further forward a couple millimeters, but my arms are cut too short, so I need to make new ones.  If I make new ones, Then an elegantly designed 3d printed part would be the way to go, and I haven't got around to that yet. :) 

IMG_2092.jpg.c72af798bb348bebf2aa81abd6c69603.jpg

As for the Spur gear, I haven't driven it much yet.  I've only put 1 battery pack or so through it.  I switched to a 13.5 brushless motor but haven't taken the opportunity to run it much.  I know the 17.5 'stock' class runs around 6:1 ratio, so it may benefit someone trying to run in that class.  For a 13.5 it seems ideal is somewhere around 7:1, so this spur is maybe to aggressive for the motor I have.  I need to run it for a while and check temperatures, and check on the gears too.

Share this post


Link to post
Share on other sites
2 hours ago, SlideWRX said:

MORE ROD!!!! :D 

3454808 is the Tamiya part number.  It is the Steering Bridge for the TB-03 VDS, currently on sale at Tamiyausa.com for ~$14.  I searched online what I could find of steering bridges, and this one looked roughly the right length so I bought one to try out.  In operation, I haven't had any big troubles.  I added a spacer to The 'L' arms (shown below) to flatten out the sweep of the arm to reduce the last bit of bump steer when turned full lock.  I had to trim the servo horn a bit to clear the steering bridge.  I can't get a good pic of that without pulling it all apart, but you can kinda see in the pictures that the blue bridge gets really close to the white servo horn.  When turning it contacts it.  I could lengthen the 'L' arms to push the bridge further forward a couple millimeters, but my arms are cut too short, so I need to make new ones.  If I make new ones, Then an elegantly designed 3d printed part would be the way to go, and I haven't got around to that yet. :) 

IMG_2092.jpg.c72af798bb348bebf2aa81abd6c69603.jpg

As for the Spur gear, I haven't driven it much yet.  I've only put 1 battery pack or so through it.  I switched to a 13.5 brushless motor but haven't taken the opportunity to run it much.  I know the 17.5 'stock' class runs around 6:1 ratio, so it may benefit someone trying to run in that class.  For a 13.5 it seems ideal is somewhere around 7:1, so this spur is maybe to aggressive for the motor I have.  I need to run it for a while and check temperatures, and check on the gears too.

Thanks. I'll have a look into that. I wondered about a vertical shaft either side, fixed top to bottom, on which could swing standard links on their bearings. But options to mount that are limited. 

Could you tell me the eye to eye length of that TB-03 steering bridge?

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, BuggyDad said:

Could you tell me the eye to eye length of that TB-03 steering bridge?

~64mm for the steering arms, ~66mm for the 'L' arm connections.  They are just slightly different one to the other.

Quote

I wondered about a vertical shaft either side, fixed top to bottom, on which could swing standard links on their bearings. But options to mount that are limited. 

The front suspension is tilted at 25 degrees and the two connections points I used seemed to be the closest I could figure out at 30-35 degrees, to keep the swing of that arms almost in-plane.  I thought about using bearings, but you would have to look at a lot of arms and yeah, mounting would be complicated.  The ball joints technically add in some looseness, but in reality it isn't significant.

Share this post


Link to post
Share on other sites

Ah ha. Thank you. I'll have a play. 

Mine comes out a bit narrower for same length steering arms and suspension arms. C.56mm. I've got Schumacher uprights in there on which the balls are some way inboard, so Ackerman already relatively pronounced. And I half wonder whether this set up has already (accidentally) improved bump steer a fair bit vs stock. It's possible the ball joint is a bit higher too. 

Share this post


Link to post
Share on other sites
20 hours ago, BuggyDad said:

Ah ha. Thank you. I'll have a play. 

Mine comes out a bit narrower for same length steering arms and suspension arms. C.56mm. I've got Schumacher uprights in there on which the balls are some way inboard, so Ackerman already relatively pronounced. And I half wonder whether this set up has already (accidentally) improved bump steer a fair bit vs stock. It's possible the ball joint is a bit higher too. 

Iirc the bump steer is significantly improved by using the schumacher uprights. A combination of ball stud position and the mounting of the hubs themselves 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...