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ThunderDragonCy

Project Ultra Hornet

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Great pics @ThunderDragonCy! One epic project,

and so good looking with the 90´s neon theme!

If I´d ever run a Grasshopper, it would be one of your conversions.

Would the concept with the Top Force gearbox in principle also work on the GH1 chassis? Or ist it too different from the GH 2 plattform?

I´m not the expert in the rigid beam platforms!:ph34r:

Looks you had great fun, awesome tracks by the way!

Kind rgards,

Matthias

 

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6 hours ago, ruebiracer said:

Great pics @ThunderDragonCy! One epic project,

and so good looking with the 90´s neon theme!

If I´d ever run a Grasshopper, it would be one of your conversions.

Would the concept with the Top Force gearbox in principle also work on the GH1 chassis? Or ist it too different from the GH 2 plattform?

I´m not the expert in the rigid beam platforms!:ph34r:

Looks you had great fun, awesome tracks by the way!

Kind rgards,

Matthias

 

Thanks Matthias. I'm glad you like it. 

Actually the Top Force gearbox is least suited to those original GH1 chassis. The transmission mounts on the GH2/Rising Fighter tub are much larger and totally different to the GH1/Hornet.

One of my friends at the weekend has decided to do a conversion based on his GH1, and we found that the solid transmission mounts from the GH1 are perfect for mounting the Thundershot transmission. He just needs to make some spacers for the bottom transmission mounts of the Thundershot gearbox to help it meet the GH1 transmission mounts. Then it's a matter of using ball connectors on the top transmission mount to the GH1 shock mount to set the angle, then make a pair of brackets out of plasticard for the middle Thundershot transmission mount so you can drill through them and the side of the GH1 rear sections to put some screws in. Like this:

This is all based on Ultra G though, so have a look there. The GH1 looks super easy to convert though. Oh, and my front GH2/Rising Fighter 4 bar suspension mount block also fit the GH1, so you can convert the front end to good suspension easily too. Excited for some more people to build these! Feel free to DM me for parts advice.

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Great pictures!

I somehow totally missed this thread, so I liked my way through it :D

Fantastic work!

Instantly makes me want to work on a buggy, too :P

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4 hours ago, ThunderDragonCy said:

Thanks Matthias. I'm glad you like it. 

Actually the Top Force gearbox is least suited to those original GH1 chassis. The transmission mounts on the GH2/Rising Fighter tub are much larger and totally different to the GH1/Hornet.

One of my friends at the weekend has decided to do a conversion based on his GH1, and we found that the solid transmission mounts from the GH1 are perfect for mounting the Thundershot transmission. He just needs to make some spacers for the bottom transmission mounts of the Thundershot gearbox to help it meet the GH1 transmission mounts. Then it's a matter of using ball connectors on the top transmission mount to the GH1 shock mount to set the angle, then make a pair of brackets out of plasticard for the middle Thundershot transmission mount so you can drill through them and the side of the GH1 rear sections to put some screws in. Like this:

This is all based on Ultra G though, so have a look there. The GH1 looks super easy to convert though. Oh, and my front GH2/Rising Fighter 4 bar suspension mount block also fit the GH1, so you can convert the front end to good suspension easily too. Excited for some more people to build these! Feel free to DM me for parts advice.

That sounds very promising with the Thundershot parts! Of course, your Ultra G is as well a top project! At the moment I´m quite busy with my Avante platform cars and the reorganization of my man cave (Moving into our new home 12 months ago), but I´d totally love to build a nice performing Grasshopper in the future! For sure, then you are my first contact person!;)

Kind regards, and much success for your friends conversion! Maybe you can organize some pics for us, when he was successful in the end!

Matthias

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Fabulous! I’m finding my own way through some upgrades to a Super Hornet; somebody pointed me to this thread. 

I am focusing on the front for now; started with a Project CRP front suspension conversion. I have to build my own steering setup because I modified things to make room for a giant 8000MaH 2S LiPo and now the steering servo doesn’t fit in the standard location. I have a plan and some parts on the way, but I’m just guessing what’s going to work!

As of today, I have everything but the steering functional — including a 2.4GHz radio set with a dual stick Futaba controller (I despise pistol-grip controllers) and an ESC. 

Once I have the front sorted, I am interested in an IRS conversion like you’ve done. The parts lists are much appreciated! It seems like you have the front-end and rear-end stuff mixed together though, which will be fun to pick through when the time comes.

 

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2 hours ago, JakeRobb said:

Oh, I forgot to ask: what software do you use to model your parts?

Thanks for having a look. Your project looks cool, and you have the proper Super Hornet shell! Bit jealous 😉

As mentioned above, the Thundershot transmission is the easier conversion, but I can send you CAD outlines for the carbon plate and put the 3D printed bits on my Shapeways store if you want to go with the manta ray transmission. 

I use Solidworks CAD. I have it for work. 

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21 hours ago, ThunderDragonCy said:

I can send you CAD outlines for the carbon plate and put the 3D printed bits on my Shapeways store if you want to go with the manta ray transmission.

I might like that. Not yet ready to pull the trigger; I want to get the steering sorted and then enjoy it as-is for a bit before I decide whether I want to spend more time and money on that — so don’t go to the effort on my account just yet!

If I did decide to do it: I care less about which conversion is easier and more about other characteristics. Is one or the other lighter? Offer more travel? More adjustability? Better geometry? Look better? More durable? Etc.

I’ve been away from the hobby for a seriously long time, so I’m not familiar with the Thundershot or the Manta Ray — and I’m not even super clear about what’s different between a Hornet, Super Hornet, Grasshopper, GH2, or any of the other similar buggies.

I’ve never used Shapeways before, nor done any sort of 3D printing. I did a tiny bit of CAD like 20 years ago, but nothing like SolidWorks. I’d love to learn to use it someday! I just checked and you can get a “maker” license for $99/year, which is pretty palatable for me.

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Jury is still out on which transmission is better, they are just different. If you want to run modern brushless, I would go with the Thundershot transmission. The open diff isn't a particular drawback if you aren't racing, and modern tyres have so much grip that even on slippery surfaces it still gets the power down. Although that is also in part due to the very long travel of the suspension being able to keep both wheels in contact with the floor in corners. It was surprising how much better Ultra G with the Thundershot rear end was on a slippery astro track compared to the theoretically superior Ultra Hornet with its ball diff. That said, I definitely improved Ultra Hornet with softer springs, and I think some more setup would get it there too. Main issue with Manta Ray/DF01/Top Force transmission we have here is they are really low geared and not known for their durability. Fine if run high rev, low torque brushed motors (which I intend to in this), but no good for Brushless. By totally coincidence, Thundershot gearing is perfect for brushless, its got great big coarse gear teeth, and parts are plentiful and cheap. I did this project as a kind of "because I can/can I do it", but really the Thundershot rear end is probably better. 

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6 hours ago, ThunderDragonCy said:

the Thundershot rear end is probably better. 

Cool, thanks for the explanation. More travel is something I’d prioritize; most other aspects are tunable. 

You mentioned the Thundershot’s open diff; isn’t the MR’s ball diff also open? I don’t have any experience with ball diffs, although from what I understand, I guess if you have the ability to adjust clamping force of the thrust washers against the balls, you could create a bias, but if I’m thinking about this right, that would create the opposite of the desired behavior — preventing slip at low torque and allowing it at high torque, rather than the other way around. 

The only diff tuning lever I’ve heard about in RC is the viscosity of the diff fluid, and AFAIK that’s applicable to both ball diffs and gear diffs.

 

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1 hour ago, JakeRobb said:

Cool, thanks for the explanation. More travel is something I’d prioritize; most other aspects are tunable. 

You mentioned the Thundershot’s open diff; isn’t the MR’s ball diff also open? I don’t have any experience with ball diffs, although from what I understand, I guess if you have the ability to adjust clamping force of the thrust washers against the balls, you could create a bias, but if I’m thinking about this right, that would create the opposite of the desired behavior — preventing slip at low torque and allowing it at high torque, rather than the other way around. 

The only diff tuning lever I’ve heard about in RC is the viscosity of the diff fluid, and AFAIK that’s applicable to both ball diffs and gear diffs.

 

Manta Ray does have an open diff, but the same gear case has a ball diff option, which I have got here. More modern ball diffs are adjustable depending on clamping force, but these Top Force diffs only have one setting. They just add a bit of limited slip in slippy conditions. Oil filled geaf diffs aren't available for either of the gearboxes used on my two buggies, but as you say, thry are much more easily tuned. Moot point here though. 

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Couple of tweaks to Ultra Hornet whilst I had the tools out. First was a change of setup to try and get a bit more rear traction. The softer spring I put on at the track helped, but it was bottoming out on bigger bumps and still not great on the power.

So, I read back through Ultra G and noticed that got some stiffer front springs to stop if diving so much under braking. With a brushed motor here the off throttle motor braking is a bit harder than the brushless in Ultra G which increases the weight transfer. As a result, the front got some Tamiya trf501 yellow front springs. 

Step two was lighter damping at the rear. All the setup guides say this gives more traction and less steering, so out went the Tamiya kit 400 oil, and in the absense of anything else in the toolbox, some 300cst yeah racing oil from the rally dampers I got for my FF03 went in. 

I left the soft springs on, but added another thick preload clip to even out the ride height. 

Second thing to address was speed! Although the Reedy Rage Type R stock race motor was nice enough, it wouldn't pull a particularly big gear without getting very hot. I had a look at the top force gear chart and said the 18t pinion I am running was suggested for the Dynatech 02R which was a 13x2. I found this on clearance at DMS 

20221204_164247.thumb.jpg.35dd973c3a1e33dab3ce659660ccf943.jpg

Never heard of them before, but Peak Performance 14x2 looks good and has adjustable timing. Should be a fair bit quicker. Hope it works out! 

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Okay, let's talk about steering.

If you are still following my thread, you might know that I got things working enough for a test drive, but completely ravaged the steering in the process -- and that my hopes for a more robust setup did not work. Specifically, I bought this upgrade kit for a Traxxas Slash in hopes that I could fit it. No such luck!

I like what you've done with steering, but I'd like to try to take it a bit farther. Here's what I'd hope to change relative to your Ultra G design:

  1. Switch sides on the arm that goes from the pivot to the servo. My huge LiPo's wires would interfere with yours as it crosses over the body. (It sounds like you did this on Ultra Hornet already, to clear the driver.)
  2. Introduce some parallelogram geometry, with the sides matching the length of the steering arms as closely as possible.
  3. Try to get points where the tie rods connect to the parallelogram to be as close to the lower A-arm pivot points as possible. 

The point of #2 and #3 would be to minimize bump steer. I don't have a good CAD system, but here's a relatively crude drawing (Ultra G on the left, my proposal on the right):

image.thumb.png.aad8cf5d0ab98dc051ce9b0c426847f6.png

One thing I'm curious about on yours is the size of the central pivot. Did you use that size for strength?

On your setup, the lower control arm pivot point is much farther outboard than on mine, so this might work out better for me than for you. You could move things outboard, but I don't think that would leave enough room for articulation. Regardless, I think it would be a slight improvement on your setup.

What do you think? Any chance you'd help me turn this into a real design and figure out how to bring it to life? I'm hopeful that it has enough articulation without the sides of the parallelogram hitting each other. I also like that the lateral connecting bar between them will offset the tie rods down a tiny bit, bringing them closer to parallel with the lower A arms. 

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3 hours ago, JakeRobb said:

Okay, let's talk about steering.

If you are still following my thread, you might know that I got things working enough for a test drive, but completely ravaged the steering in the process -- and that my hopes for a more robust setup did not work. Specifically, I bought this upgrade kit for a Traxxas Slash in hopes that I could fit it. No such luck!

I like what you've done with steering, but I'd like to try to take it a bit farther. Here's what I'd hope to change relative to your Ultra G design:

  1. Switch sides on the arm that goes from the pivot to the servo. My huge LiPo's wires would interfere with yours as it crosses over the body. (It sounds like you did this on Ultra Hornet already, to clear the driver.)
  2. Introduce some parallelogram geometry, with the sides matching the length of the steering arms as closely as possible.
  3. Try to get points where the tie rods connect to the parallelogram to be as close to the lower A-arm pivot points as possible. 

The point of #2 and #3 would be to minimize bump steer. I don't have a good CAD system, but here's a relatively crude drawing (Ultra G on the left, my proposal on the right):

image.thumb.png.aad8cf5d0ab98dc051ce9b0c426847f6.png

One thing I'm curious about on yours is the size of the central pivot. Did you use that size for strength?

On your setup, the lower control arm pivot point is much farther outboard than on mine, so this might work out better for me than for you. You could move things outboard, but I don't think that would leave enough room for articulation. Regardless, I think it would be a slight improvement on your setup.

What do you think? Any chance you'd help me turn this into a real design and figure out how to bring it to life? I'm hopeful that it has enough articulation without the sides of the parallelogram hitting each other. I also like that the lateral connecting bar between them will offset the tie rods down a tiny bit, bringing them closer to parallel with the lower A arms. 

I couldn't work out how to fit a parallegram otherwise I would have. Main issue on that is the big drop in height from the parallelogram arms to wear the connecting bar needs to be.

The pivot is 5mm diameter DB01 steering post, but you could use 850 bearings to make it smaller. You could use an M3 bolt and 730 bearings I guess. 

Best thing I can suggest is get the M05 B Parts sprue. That has a really small parallelogram and there is probably a solution in there somewhere, but I haven't worked it out yet. 

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32 minutes ago, ThunderDragonCy said:

I couldn't work out how to fit a parallegram otherwise I would have. Main issue on that is the big drop in height from the parallelogram arms to wear the connecting bar needs to be.

I'm looking at your picture, and I can't figure out what you have beneath the pivot. I assumed it was just a couple of ball screws to attach to the turnbuckle. No?

image.png.277ed95074574da63226dd5d44d848ef.png

 

Quote

The pivot is 5mm diameter DB01 steering post, but you could use 850 bearings to make it smaller. You could use an M3 bolt and 730 bearings I guess. 

Okay. What bearing do you have in there? 1150? Any particular reason you went with that? My setup would be distributing load across two bearings, so it seems reasonable that I could go smaller.

 

Quote

Best thing I can suggest is get the M05 B Parts sprue. That has a really small parallelogram and there is probably a solution in there somewhere, but I haven't worked it out yet. 

 

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@JakeRobb Underneath the screws he part had the thick tab to drop blow the tub to the right level for the steering arms. The screws are m3x20 into ball screws.

The bearings are two 1150. Partly because I had them in my spares and I was designing the parts, partly because the db01 steering post is 8mm tall so two 1150 is the right thickness. Massively over spec really. My TRF211 runs 630 bearings in the steering with no bother

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Ran at Tamiya Junkies meet at Robin Hood Raceway. Don't let the pic fool you: I only ran outside 3 laps dodging massive puddles, before heading back inside to the flat astro track. 

20230114_102705

 

Such a fun time, and it was nice to spend some time getting Ultra Hornet a big more dialed in. Last time it was struggling for traction a bit. Lighter rear oil and Schumacher Mezzos and the opposite was true! Ended up stiffening the rear springs to DF03 soft black, and fronts back down to TRF201 brown. Tweaked steering a little, and shifted the shorty battery all the way forward, but never got it quite as dialed as Ultra G. Was still really nice to drive though. 

Eventually I flipped it off a ramp and the front tower snapped. Took me 4 years to do it on Ultra G, and this was about 5th run! I think my mistake was having too long screws holding the shock mounting brackets, which stuck clear of the nuts, dug into the astro and snapped it. Need to sort a carbon tower, but not the same as Ultra G. I would like this one to not need body mods. Things to do! 

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Been a bit quiet on this. Realised a couple of weeks ago that I wasn't going to need any 3d printed bits for a while, which put the front tower for ultra hornet on ice as I would have any way of mounting a carbon plate. I wanted to get it running again though, so I bought a new tub as a means of fixing the broken front tower. Seems a bit sledgehammer to crack a nut, but at under £12 posted it was definitely cheaper than the carbon plan! 

Needed a bit of spare time to have a run at this as anew tub needs a lot of prep. Cutting, drilling and tapping threads. 

Got it back together this evening, but with a tweak. If you read earlier on in the thread I originally had a front arm block with more kick up, but it made the arms hit the carbon plate for inner camber link mounts. Since then, m'colleague @graemevw has built a Grasshopper 1 conversion like Ultra G, but made front camber link mounts by modifying the bumper bosses. Genius!

Firstly you cut the domed tops off the side bumper bosses like so

20230212_172946

Then you drill through with a 3mm drill. Once you have the front arm conversion assembled, mount the bumper and pass a long M3 screw through the boss. Attach a ball nut on top and kerchow! Inner camber link mount. 

Graeme's Grasshopper with my usual lower kick up front just mounted the ball nut on top of the boss. Here, this allowed me to use the high kick up block, but that put the arms higher at the front, so I needed a m3x30 screw, 6mm cva spacer, 1.5mm alloy spacer under the ball nut before it came together 

20230216_205839 20230216_205903

 

I also put ball nuts on the shock towers and mounted a cross brace to hopefully keep these in one piece longer! 

From the top this does give quite an offset to the links but it seems to work on the bench. No weird bumpsteer or other obvious oddness. 

20230216_203537

Won't know anything for sure until I get to run it though.

Whilst I had it apart changed the front shock oil from 500cst to 300cst to match the rear. I was struggling for front end when I last ran at the track, so some softer oil will give some more grip. The idea with more kick up is more weight transfer forward under braking too, so let's see if it works. 

 

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Had a spare hour this afternoon, so I charged up a pack and gave the rebuilt Ultra Hornet it's maiden run. 

Tamiya Ultra Hornet

It was slightly damp and a bit muddy, but it ran nicely enough. Probably wasn't the conditions for cut stagger front tyres, but they were OK. I definitely improved things by changing out the TRF201 brown front springs for the cva set soft springs. Combined with the softer front oil (and maybe the kick up) it had nice turn in and felt a bit better balanced grip front to rear. 

On slightly slippy grass the ball diff obviously works nicely. I ran Ultra G last week on this park and I was definitely getting more diff out from the open diffin that car. I wish someone would make a proper diff for the Thundershot chassis! 

Anyway, the other thing that was a bit hinky was the short, swept forward camber links. They were OK, but I had a suspicion yesterday they wouldn't be great, so I hedged my bets, measured the upper arms on my dt03 (this uses dt03 lower arms), drilled the tub, and mounted some ball nuts inside the body so I could try some camber links similar length to the dt03. I had to dremmel the corner of the body off just ahead of the shock tower, but it was a fairly small cut. Anyway, I swapped these in and the front definitely felt better. Just a bit more consistent. I guess the front bumper mounting only works with the Thundershot arms and less kick up.

Here's a shot of the long camber links. I would be lying if I said I didn't prefer the look with everything more in line

Tamiya Ultra Hornet

To be fair, Ultra G with Thundershot arms is completely different geometry, and I have driven @graemevw Grasshopper conversion and its lovely, so bumper mount definitely works there. 

The main other thing I have noticed is the front rides quite high, and the tub doesn't hit the floor before the shocks bottom out. Ultra G has fairly high ground clearance too, but does just bottom out the tub before the shocks. The DT03 arms just sit higher. Not sure what do. I guess next I get 3d printed parts I can do the carbon tower conversion with the shock eyelets raised up a few mm compared to the tub tower. Other 3d print option would be another front block the drops the inner arm mounts down a little. That would help a bit. We'll see. 

Anyway, it's running nicely, but it really seems I lucked out with Ultra G and how it just hung together nicely. Here's a bit of running 

 

 

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Didn't manage to get a pic, but ran at the track again. New front end geometry is so much better. Was quite tricky today, with the two astro tracks being crazy grippy making my usual softer setup for bumpy grass a bit edgy. Once I got my eye in and took a preload spacer out the back to lower the ride height if was great. Its REALLY fast with that new motor, and not that smooth on the throttle pick up. Bit like you have too much punch on a brushless setup. Nitpicking though. It was lovely. My mate how built a Grasshopper conversion based on Ultra G had a go and said he though it felt a bit more refined. That was the original idea, so that's nice. 

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Track day! 

20230715_103611

Astro was damp but drying and the track layout was bumpy and technical, but really fun. No big jumps, which is good, because I am rubbish at jumps. Ultra Hornet was running really nice. The esc randomly died on my a few weeks back and I was wondering if that 14x2 motor might be the culprit. I got a Carson dragster esc this week and put the Reedy Rage 27t stock Racing motor back in, but with a bigger 20t pinion this time. I think I found the sweet spot. It's quick enough on the long straight, but picks up so much more smoothly from closed throttle. 

Only change I made was moving the balls on the knuckles inboard after doing same on the Hotshot2 worked so well. 

20230715_132008

I think this must be the stock dt02/3 position with the longer hole an addition on these aluminium uprights. Whatever it is, it improved the steering feel and I ended up running Ultra Hornet loads today, indoor and out. I think it's the first time since I built if I preferred it to Ultra G. Was settled, but predictable and fun. Loved it! 

 

 

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Track day! 

FB_IMG_1700344906386

 

FB_IMG_1700344877455

On the grippy indoor astro the initial balance was very understeer, but it's been running minipins on the rear which are very grippy on this surface. After running another buggy I swapped onto minispikes and it balanced right up. Really fun, fast running. Lovely! 

 

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