ThunderDragonCy

Thunder Dragon - Ongoing Chassis Development - now with TRF suspension

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1 hour ago, mman2005 said:

Glad you got the setup you want Cy! Feel like I've been through it with you :D This thread gives me plenty to think about when I decide I want to have a play with mine. For now I have an old pair of original tyres that have gone slick. Great fun getting the back end out.

You definitely need to get one of yours up and running. Just get some cheap 2.2 wheels and tyres and run on, and with any of the other bodies you don't have the issues with twin shock fit, and I'm sure with some tuning the front mono could work OK if you kept the roll bar. This rear setup is so nice though. 

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Update! I smashed my 3d printed front shock mount last week when it flipped out of a compression at the park. Didn't have time/funds to get another in time for the track day I should have been at this weekend. Only option was to use the original mount. Having played with this a little earlier in the summer I knew it allowed a lot of movement, and so bit did! After trying a few things I have ended up with a 3mm spacer inside the front shocks and the long eyelet giving 67mm length. Mounted on the outermost hole on the wishbones (which is different to the original Thunder Dragon CVA hop up. That used 64mm shocks and the third eyelet in the wishbone) this gives nice ride height and the shortened shock reduces the weight transfer and pitch. Had to use the hardest front springs I have (the original vintage twin shock springs, possibly a little harder even than the hard DF03 springs) but it works really nicely. 

20180923_155103

Also taken the slightly mental 4000kv 10.5 brushless out and got another brilliant speed passion 13.5R MMM 3300kv from Modelsport. Still plenty fast but nice for this chassis.

Finally, as I bl***y mindedly want to stick with my 2" wheels and I run mainly on grass I decided to try to give the rear more grip with new tyres. Schumacher full spikes! They work brilliantly and balance out the Mini spike fronts to give the car the nicest front to rear balance I have found. If you run 2.2s I am sure mini spikes rear and cut stagger fronts would do the same job. They look mean too!

20180923_155107

 

 

 

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Ran at the track last weekend and unfortunately the Thunder Dragon was a bit of a floppy handful with that old front mount. Just too soft at the front and lots of turn in oversteer. Looked nice out there though 😉

Tamiya Junkies Robin Hood Raceway meet 20th octoberTamiya Junkies Robin Hood Raceway meet 20th october

So I needed the front to be at stiffer. I dug out one of my earlier 3d printed shock towers to mount the shocks wide again and go back to the c hub pivot bottom shock mounting I figured out earlier in the summer. I left the super stiff springs on and put the front roll bar back on for good measure. Old Thunder is a heavy old bus so I need to keep that weight in check! Was definitely better, but it was still suffering that twitchy fast turn in I have been wrestling with forever. So I got reading about Ackerman steering as more ackerman should calm the front end down. As stock the chassis doesn't have much ackerman (so the inside wheel turns about the same as the outside which makes it twitchy). As I run the DF03 uprights in my 10deg caster c hubs I had the option of adjustment here. Seems the front holes give more ackerman. Then I found a page on rcscrapyard that said angling in the steering wipers helped. I uncooked the servo and tested it out and low and behold, much more steering on the inside wheel than outside I.e. more ackerman. So I set it up with as much angle as possible and had a run out and it feels a lot better. Fingers crossed. Here's the steering setup now

Improved Ackerman on the Tamiya Thunder Dragon / Thundershot / Terra Scorcher / Fire Dragon chassis.Improved Ackerman on the Tamiya Thunder Dragon / Thundershot / Terra Scorcher / Fire Dragon chassis.

I have my own design steering wipers arms with bearings and ball end link so it was easy for me to shorten the link. On the stock arms you can probably install ball screws in the hole where the wire link goes, or shorten the wire link and re-bend it. It is approximately 57mm between the link hole centres now.

I had to lengthen the steering arms a fair bit, but I just used some M3 threaded rod I had spare.

Hopefully you can see more angle on the inside wheel than the outside

Improved Ackerman on the Tamiya Thunder Dragon / Thundershot / Terra Scorcher / Fire Dragon chassis.

 

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Slightly off piste here, and not tested yet, but I have found that a combination of TRF201/501/DN01 rear arms 54142 or 51449 and DT02/3 rear hubs fits the Thundershot chassis. Arms need drilling out to 3mm at the ends to fit the hubs, but it fits. 

TRF501 DB01 TRF201 rear arms on a Tamiya Thunder Dragon using DT03 hubs.TRF501 DB01 TRF201 rear arms on a Tamiya Thunder Dragon using DT03 hubs.TRF501 DB01 TRF201 rear arms on a Tamiya Thunder Dragon using DT03 hubs.

 

More if or when I run it. 

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If they are longer do you also not require longer drive shafts? Or they may fall out!

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Could you fill the hubs with epoxy and redrill them to save the arms?

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1 hour ago, Baddon said:

If they are longer do you also not require longer drive shafts? Or they may fall out!

No, the shafts fit perfectly because the DT03 hubs are way shorter than the Thundershot version. I tried the TRF rear hub and the shaft was actually too long for that. Wouldn't fit. 

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30 minutes ago, Nobbi1977 said:

Could you fill the hubs with epoxy and redrill them to save the arms?

Not a bad shout. I have some araldite. I have shimmed the hubs properly now and they aren't too bad, so I might just do a quick proof of concept (or not) run as is before deciding what to do. These are spare because my DT03 has some 3D printed 3 deg toe in hubs I designed, so if it looks promising I could tweak the model on those with a smaller hole so it would all work. 

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Ran a pack through it at lunch time to see how it went

Tamiya Thunder Dragon orange with TRF rear suspensionTamiya Thunder Dragon orange with TRF rear suspension

Answer is...... very promising! Rear end seemed much more settled and much less bouncy than when I ran in the same place earlier in the week. Balance was nicer. Still turned in pretty sharply, but the rear seemed to have the capacity to live with the front. Less turn in oversteer. I think this might legs! More testing and tinkering to do I think. 

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Further down the rabbit hole today. Some DB01 spares borrowed from a friend. If you are using universal driveshafts the front suspension just fits straight on. No bother at all. 

Tamiya Thunder Dragon / Thundershot / Terra Scorcher with DB01 / TRF front suspensionTamiya Thunder Dragon / Thundershot / Terra Scorcher with DB01 / TRF front suspensionTamiya Thunder Dragon / Thundershot / Terra Scorcher with DB01 / TRF front suspension

No running yet as I didn't buy the kingpins until I knew it would work. Goes together with no bother, just a 1.5mm spacer in front of the arm on the inboard end to take up the gap to the A5 part. Only other slight modification was needing to dremel the ribs inside the Egress wheels a couple of mm near the rim to clear the steering knuckle. The 2.2" wheels fit fine. 

Can't wait to give it a run. Whole thing just feels so much more solid and lacking in slop. 

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Ran it this week. It's brilliant! 

Tamiya Thunder Dragon with TRF501 suspension

Handles so much more calmly than the original. More control, smoother, more fun to drive. Might do some dedicated rear hubs with some toe in, adjustment but mainly to increase ride height a little. Compared to the TRF hubs the DT03 hubs sit the axle about 5mm higher.

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I have been running the buggy a few more times and I absolutely love it. Suvh nice settled handling. However there was one thing bothering me: The ride height at the rear is a bit low because the DT03 rear uprights have a bigger offset from the pivot to the drive axle centreline than the TRF uprights. It's around 12mm vs around 7mm on TRF or xv01 uprights. I am guessing this is because DT03 arms are flat and TRF arms are gull wing. They DT03 uprights also have no toe in and no adjustability. Seeing as the reason these are spare is because I designed my own 3 deg adjustable uprights for my DT03 seemed obvious what the next step needs to be..... 

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

These aren't my DT03 design 3deg uprights. As I said, I wanted to correct the ride height, and also the extra thick material around the pivot on my DT03 parts don't fit the TRF arms. I measured up the xv01 uprights on my TRF211 and got the axle centreline within 1mm of that part and the top of the adjuster surface the same 12mm above the pivot. I put three holes in which needed m3 tapping for a regular 5mm ball screw. And of course, 3 deg of toe in. I also took a leaf out of the TRF uprights book and included a spacer (the white ring in the picture) to place between the bearings.

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

I have some hexes with the step drilled out which I use occasionally on the TRF buggies. I used these and can now tighten the wheels down hard on the bearings for smooth spinning and no slop. 

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

Spare 3 x 32mm turnbuckles from the DT03 set that were spare. 

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

The other thing I noticed with it all apart was some slight binding around the outdrives. I dremel'd the inner arm to clear and I also ran my 3.1mm drill through the inner pivot hole.

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

Unlike the TRF cars the arms here ideally need to pivot on the axle so this freed them up nicely. 

I needed an o ring in the gearbox outdrives and one of the ball diff urethane bumpers cut in half in the wheel end to space the dog ones perfectly. Now all runs super smooth with no binding

Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.Tamiya Thunder Dragon with TRF suspension. Custom 3d printed CTE RC 3 deg toe in uprights with adjustable arm length and corrected ride height.

I am excited to run it set up properly. With the new uprights I should have a little less oversteer on turn in, bit more rear traction on the throttle which should hopefully get the balance spot on. 

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Quick update : Ran at the track last weekend. Unfortunately the indoor flat carpet with a couple of kickers instead of the outdoor. However the Thunder Dragon continued to be lovely drive. Less good was that the uprights didn't survive contact with the track. One snapped at the ball screw hole and the other ball screw was halfway out. Not ideal! I have beefed up the design and switched to a horizontal through bolting design instead of the vertical threading in option. This design was solid on the previous 3 deg uprights I did for the original blue arms. Just waiting for a bit of spare cash to order them.

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Been running for the last few weeks with the DT03 uprights and it's been ace. However today I got Version 2 of my rear uprights to correct the ride height. Here bottom right with some other goodies, including a hopefully improved bearing steering set. More of that another time. 

20190221_161720

Here's the DT03 upright

20190221_161720

And with the new one

20190221_205708

Changed from threaded in ball screws which failed at the track to through bolted ball nuts. Retained a bit of adjustability for roll centre with three height and two arm length options. Even this highest, shortest arm setting is lower and further out than the DT03. Had to dig out some longer 45mm turnbuckles out of the spares box. Lower and longer arms gives a lower rear roll centre, so more roll, more grip, less steering. 

Had a pack charged so got a long run in just before dark

20190221_172151

Small but noticeable improvement. Rear ride height more sensible so I could back off the preload and just more rear grip and cleaner on the power out of turns. Very nice. Made my lovely buggy even more lovely. 

Steering mods and a couple of other things up my sleeve soon. 

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This is almost a surprise to me this one. Carbon shock tower with a difference. Been thinking about a carbon tower as the Terra Scorcher tower is very flexy. 

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

Was chatting weak spots on the chassis on a Thundershot group and someone mentioned the top suspension pick ups always cracking. Indeed, my rear ones are cracked and I recently had to write off a perfectly good front gearcase because I broke one.

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

Exhibit A

The guy reckoned the issue is the screwpin threads stressing the plastic and eventually cracking it. Got me thinking about how to reinforce them and ditch the threads. Can't do shafts and e-clips because there is nowhere to anchor them on the inner side. So I came up with this. 

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

Notice the extensions down towards the screwpin holes. The gearbox is completely flat behind so the plate bolts straight. Apart from a couple of extra holes at wider positions for the shocks this is the same as the Terra Scorcher / Fire Dragon mount. Inner holes are same as the original. 

You might be able to spot where this is going from this view

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

M3 x 12 screw and a standard tamiya ball nut

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

The mount is reinforced, not threaded, and the shock tower now has 5 fixing points. 

And all back together

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

Tamiya hard rod ends on the 32mm turnbuckles. Solid mounting, no slop. Not had a chance to run it but I am very happy with this solution. Really hope its solid. 

And a final little touch. Without the moulding on the original mount I needed to space out the top of the shocks. All hail the usefulness of the blue Thundershot spacers! 

Tamiya Thundershot Thunder Dragon Fire Dragon Terra Scorcher carbon shock tower with pivot pin reinforcement

I have a front one which should work the same way, but I have some body mount fitting things to figure out first. 

What do you think? 

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Your Dragon is going to end up with carbon double deck chassis plates and only running thundershot gearbox's lol

 

I am really enjoying your mods, I would love to see a running vid some day 

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53 minutes ago, Snappy1 said:

Your Dragon is going to end up with carbon double deck chassis plates and only running thundershot gearbox's lol

 

I am really enjoying your mods, I would love to see a running vid some day 

Haha! Don't think I haven't looked at it. Those side carbon plate Hotshots did get me thinking, but I think anything like that will end up heavier than the tub, so I am quite happy for now. I am trying to stay true to the spirit of the car, but the arms are sooooo much better than the blue ones! 

I am thinking of finding a scrap tub to see if my shorty idea will work. I think there is space for a shorty longitudinally if you remove all the ribs but I don't know how I would get it in and out easily. 

Next time I am at the track I'll get one of the guys to get some footage. It moves really well now. 

Cheers! 

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Version 2 of the bearing steering set. I have been running the bearing pivot arms for a while, but there's still loads of slop in the system from all the ball cups. The moment one gets a little worn it just amplifies through the whole steering. So, taking my cue from my TRF buggies, I designed a new one

20190301_111224

Now uses a solid cross link arm with recesses for the M3 nuts as you can see so it clears the 'sump guard' of the bumper. The arms have all the bearings in them

20190301_111237

A 730 bearing pushed into this large hole from the top, and it's all held together by an M3 x 8 screw. This completely eliminates any slop from the cross link.

The inner pivot works the same as before....

20190301_111249

The top nut tightens the M3 x 20 screw hard against the chassis tub to give a solid mounting. There are 2 x 630 bearings in each arm. I use 0.2mm shims top and bottom so the bearings clear the nuts, and the nut on the end is a nylock so you can take out the slop without crushing the bearings. It's still reliant on the ball cup on the steering saver link being tight, and this one very much isn't! but the rest is really tight and smooth. Some new ball screws and ball cups on the steering link and this will be super nice. Going to run it for a bit and if it stays together I'll get it on my Shapeways store.

Cheers!

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Excellent stuff Cy! Very interesting following this thread. How resilient is the white material is respect of slight bending/flexing?

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5 hours ago, ALEXKYRIAK said:

Excellent stuff Cy! Very interesting following this thread. How resilient is the white material is respect of slight bending/flexing?

The versatile plastic is fairly resilient but I definitely have to beef up the size of the parts compared to kit ABS parts to make they are strong enough. Main thing I have found is threading into it isn't great, hence the recesses for proper nuts in this part. 

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Front carbon tower and camber link mount installed. Needed a bit of filing as I didn't quite get the shape right to clear the gearcase. 

Tamiya Thundershot / Thunder Dragon / Terra Scorcher / Fire Dragon carbon front shock tower and ball joint camber link mount

Bottom pair of screws are the original mounting points. The top pair are the new camber link mounting points, replacing the screw pins. Still not sure if the anti roll bar can mount to this, but I am not running it at the moment. 

New camber link top mount using the ball nut

Tamiya Thundershot / Thunder Dragon / Terra Scorcher / Fire Dragon carbon front shock tower and ball joint camber link mount

And with the body on. I can't use the original front body mount because it usually sandwiches in a slot behind the kit shock mount. I have a shortened body mount arriving from shapeways on Monday. 

Tamiya Thundershot / Thunder Dragon / Terra Scorcher / Fire Dragon carbon front shock tower and ball joint camber link mount

The new mount is designed for 75mm shocks, not the 64mm mini cva kit shocks. These aeration dampers are swiped from my TRF201, but I think some DF03 shocks would be nice for this eventually. Looking forward to getting the body mount and seeing how the longer stroke shocks work. 

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Shapeways delivery. Front body mount fits perfectly. 

20190304_20411420190304_20410820190304_204052

Now just need it to stop chucking it down with rain so I can run it! 

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Excellent work. Enjoy watching you freaking out with your dragon. Go, go, go!

 

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