Grasshopper 2 Ultra G Evo Black Edition

[ThunderDragonCy 8380]

@BuggyDad Good suggestions all. I have put trf501 front shafts at around 40mm in front mini shocks, but it didn't appreciably increase stroke and it kept bursting the cva seal because the shaft could hit it and keep going. Ultimately i think the mini shock body is too short. 

Got no scope on the shock mount. Although i am designing it i am limited on how narrow i can go by the gh2 body.

I am leaning towards a halfway house of trf501 or df03 front shaft with the longer short shock body. That should get me the stroke i want at minimal extra length, but i haven't done any calcs in that yet.

[BuggyDad 5904]

16 minutes ago, ThunderDragonCy said:

@BuggyDad .

I am leaning towards a halfway house of trf501 or df03 front shaft with the longer short shock body. That should get me the stroke i want at minimal extra length, but i haven't done any calcs in that yet.

Ah. Good idea. I might look into that for my own one as well then. 

[Honza 1167]

Awesome project. Tamiya based/inspired custom chassis builds are becoming quite common lately 😁

Regarding this

On 1/26/2024 at 9:09 AM, ThunderDragonCy said:

Just had a look and the BBX/XV01 layshaft is shorter and quite different to the TRF201/TD4 style version. Although I am sure it could be made to work I think I will hang out for the TD4 one. The longer layshaft allows me to put the motor more central in the car which in turns fits the motor and mounting bits between the rear trans mount.

What about using a counter gear from a buggy that uses a cross pin to secure it to the shaft? Then you could make a custom layshaft with exact parameters you need.

[ThunderDragonCy 8380]

@Honza Thanks ! The TD4 already has that layout, but the countergear to diff ratio is key to the internal gearing so i don't want to mess with that. I have a layout that should work now.

[Honza 1167]

@ThunderDragonCy TRF201/FF-03 uses layout I have in mind, with the same 20T/48p gear. This just takes a 4mm rod and drill to make a custom layshaft. It's just backup idea if you're not successful in sourcing the TD4 shaft. It's been even possible to get a 20T/48p steel counter gear, before all manufacturers started making layshaft/counter gear in one piece.

[ThunderDragonCy 8380]

Did some layouts of the front with a cva2 short shock. Measuring the ones i have, they appears to have 27mm stroke at full length. According to the 50520 box the short eyelet shock is 87mm long, but that's 7mm shorter than the long eyelet, but i thought the long eyelet was only 6mm longer. So, definitely some measuring of kit shocks to be done before i finish any designs. 

Back to the job in hand though. Schumacher front shock is 22mm stroke, so with short eyelet and 5mm spacer the cva2 short shock will be 82mm full extension and 60mm at full compression. Using 60mm as a guide i sized the front tower so the front wheel is 1mm above the tub floor at full compression. Laying in the 82mm shock from here gives full droop height of 37mm (about same as rear), and 8mm of stroke on the shock (so 30ish% shock travel) gives 23mm ride height. All of this feels good, much better than the mini shock.

The longer shock gives me more options to tweak the stroke and droop as well so fairly sure i am going to go this way. Also feels a bit dynastorm-ish, which is cool.

 

[BuggyDad 5904]

3 hours ago, ThunderDragonCy said:

Did some layouts of the front with a cva2 short shock. Measuring the ones i have, they appears to have 27mm stroke at full length. According to the 50520 box the short eyelet shock is 87mm long, but that's 7mm shorter than the long eyelet, but i thought the long eyelet was only 6mm longer. So, definitely some measuring of kit shocks to be done before i finish any designs. 

Back to the job in hand though. Schumacher front shock is 22mm stroke, so with short eyelet and 5mm spacer the cva2 short shock will be 82mm full extension and 60mm at full compression. Using 60mm as a guide i sized the front tower so the front wheel is 1mm above the tub floor at full compression. Laying in the 82mm shock from here gives full droop height of 37mm (about same as rear), and 8mm of stroke on the shock (so 30ish% shock travel) gives 23mm ride height. All of this feels good, much better than the mini shock.

The longer shock gives me more options to tweak the stroke and droop as well so fairly sure i am going to go this way. Also feels a bit dynastorm-ish, which is cool.

 

I think this is going to be a nice sort of signature element of the look of this thing.

You may well have inspired the next development step for my Falcon. Partly because it has just the same problem but partly also because the only thing better than yellow shocks on a Falcon is bigger yellow shocks. 

[ThunderDragonCy 8380]

Day of in lieu today so playing around with this a little more, and getting right into the details. And, as always, the details kick your *******! Firstly, I got the Associated 26t idlers and they are wider and use 1050 bearings, so I altered the model to reflect that. When sectioning the internals I noticed it was all looking very tight on the main shaft, so I checked some of my TRF201 and TRF211 gearboxes and realised the spacings were completely off! I had based this on my FF03 4 gear transmission as it was easier to start with that. I had assumed the layshaft in the FF03 was same as the TRF/TD4. WRONG! The shaft spacer and layshaft are narrower and shorter respectively. Seeing as I actually had a slipper clutch equipped TD4 I pulled it apart, measured it, modelled up a new slipper/spur/shaft/spacer from scratch from the measurements, and EVERYTHING went to ****! Need to re-jig all the internal spacings and bearing seats, and found the slipper nut sticks out so far it hit the shock really badly. I guess it's good to find now! 

Anyway, had to completely re-arrange the transmission to push the layshaft and spur gear 5mm further forward to miss the shock. As I can't push the motors any further forward because of the GH2 tube, that meant lifting the layshaft as well. So, it's now more of a 4 gear standup than laydown. Still, it all fits now, and it makes moving the Schumacher suspension blocks around much easier too so I think it's a win on balance.

I have also ordered a few more parts. After trawling through Plaza Japan I have got the TD4 slipper clutch, the remaining TA06 gear diff parts I need, some rod guides and o rings and piston rods to improve the shocks. Getting closer now.

 

[Wheel_Nut 376]

I am wondering about the 4 gear transmission.    Can you reduce the height of the transmission by changing to a 3 gear design?    I admit I'm not a fan of 4 gear transmission because it increases gyroscopic and inertia reaction forces.   I believe 3 gear is more popular because these forces will partially cancel between the rotation of the motor and the axles.

[ThunderDragonCy 8380]

The height of the transmission is nothing to do with the 4 gear. I have a laydown version which I designed for the TRF211 which is very low indeed. The issue here is other constraints. The motor cannot be moved further forward because of the tub bulkhead. I needed to move the layshaft forward so the slipper shaft clears the shock. The only way to move the layshaft forward when the motor position is fixed is to lift it as well, effectively moving it around the radius of the motor. The only way I could move it down would be to move the shocks to the rear of the arms. I'm not too bothered about the current position though. It's height means that the suspension is all easy to package, and although 5mm higher than before, it's also a lot further forward, so there are some advantages.

As for 4 gear, I want to do it because I like the idea and I've never done a buggy one before, and it's mechanically interesting. I know there is lots of theoretical advantages to 3 gear in terms of acceleration, but the motor rotation of the 4 gear tends to squat the rear to improve grip, and a lot of the Dirt derivative race buggies used a 4 gear until quite recently. I had a 4 gear in my FF03 to improve the grip using the motor rotation and it was really nice, and softer throttle response isn't a bad thing in my book. I guess the final thing is that the Thundershot transmission in my original Ultra G is 2 gear, so the motor rotates the same way, and I love the way that "squats and goes". The 3 gear in Ultra Hornet definitely has more drive and more immediate feel, but I'm not sure I like it more. 

[ThunderDragonCy 8380]

Oh hey!

Black body and stickers look mint. Well excited! 

[BuggyDad 5904]

If I may throw in a numpty question (I'm being thick)... 

Your desire to go for a 4 gear transmission, when 3 gear seems to be the norm, interests me. It seems to me that in a 3 gear, the diff rotating forwards = spur rotating backwards = motor rotating forwards. The big mass here is in the rotor so acceleration will tend to lift the nose and squat the rear, right? More rear grip, less front grip. Forward rotating (accelerating) wheel inertia adds to the same effect, as does the rotational effect of a forward force at the road working against a centre of mass at a higher level. 

So add an idler to reverse motor rotation for the opposite effect, and therefore in a 4 gear the torque effect of the motor is to keep the nose down and anti-squat. Reduce on power understeer, reduce rear traction? 

Or, do I have this the wrong way round, and if so, how is it explained? I think I do have it the wrong way round, because on a quick search I see reference to 3 gear doing what I think 4 gear should do. But I don't know why... 

[ThunderDragonCy 8380]

@BuggyDad You have it the right idea when it comes to reactions to the forces, but the wrong motor rotations as you've missed out a step in each. In a 3 Gear, diff rotates forwards = idler backwards = spur rotate forwards = motor rotates backwards. So 3 Gear is the one that gives you more drive towards the front wheels on power. That's why they're more popular now as surfaces tend to be high grip these days and tyres are much better. By adding the extra idler a 4 gear has the motor rotating forwards so the reaction is tending to squat the rear suspension, which is better for traction at the expense of front on power grip. This is all hand waving though. I just want to build a 4 gear because I think it will be cool ;-)

[ThunderDragonCy 8380]

@Wheel_Nut I had a look at putting the shocks on the back of the arms and moving the layshaft down, but this pushes the shaft a long way rearwards and also causes issues with idler clearances inside the transmission. Even though the layshaft has ended up a few mm higher with my current layout, it's quite far forward which is good. It's all a bit academic given that I'm bolting it all to a GH2 tub and body, but it's always good to sense check stuff.

Speaking of which, I have some Schumacher arm shafts to measure up and so all that details has gone into the model. The outer rear arm pins are only 2.3mm! I also read the Cougar KC manual which is where my rear arm blocks are from and found that the inner blocks are slightly asymmetrical to allow for 0.5 deg toe in adjustment, but I missed that when measuring as it's barely 0.5mm offset. Figured it out now, modelled up left and right versions and all the spacers and blocks I'll need. Note the flat edge on the toe in block. That's how you know which way around it is for toe in adjustment. I'll have to 3D print the red arm spacer and yellow anti-squat blocks.

 

At the front, I finally figured out how to do a front shock tower block on the inside. I don't why I found it so hard before. It's the yellow part. Also updated the c hubs (orange) to have a forward extension for the camber link so they clear the front of the shock tower (which the inner ball mounts to). 

Feels like I'm getting close now. Going to wait for my PJ package to arrive and build the shocks fully so I can check fit to the arms and measure them accurately. Once I've done that I can finalise all the carbon and printed parts and get it all off for manufacturing.

[BuggyDad 5904]

1 hour ago, ThunderDragonCy said:

@BuggyDad You have it the right idea when it comes to reactions to the forces, but the wrong motor rotations as you've missed out a step in each. In a 3 Gear, diff rotates forwards = idler backwards = spur rotate forwards = motor rotates backwards. So 3 Gear is the one that gives you more drive towards the front wheels on power. That's why they're more popular now as surfaces tend to be high grip these days and tyres are much better. By adding the extra idler a 4 gear has the motor rotating forwards so the reaction is tending to squat the rear suspension, which is better for traction at the expense of front on power grip. This is all hand waving though. I just want to build a 4 gear because I think it will be cool ;-)

Ah ha! Excellent news - this means I can be both wrong (which I kind of knew I was) and not a complete idiot. So the gearboxes I was thinking of (basic buggies eg Blitzer) are 2 gear, and that's limited to transmissions that just aren't fancy enough for people to talk about? 🤔

Helps explain why my Falcon won't steer under power and visibly squats, not helped by it's absurdly low gearing and 8.5T motor. 

Slightly concerned though that Project X (3 gear BBX transmission) is combining an obsession with moving weight forward with motor torque that pushes the nose down under power. We will see.

This has also added a new factor in my consideration of a future project. The Mega Falcon. Or, designing a 3 gear case that takes a sensible diff (and stock gears from something) for the DT-03. 

[ThunderDragonCy 8380]

Yeah, 2 gear is also the Thundershot in Ultra G, but i liked that it squats under power and gets loads of traction. I am hoping the 4 gear will do similar.

[Wheel_Nut 376]

I got a set of those XV-01 alloy bellcranks in preparation for my 2WD truck project.   I think they are a bit shorter than the one you made for the earlier edition Ultra G with blue suspension arms.  I wonder if there may be a compromise in precision for the servo linkage.  Do you see any benefit in designing a custom bellcrank with revised geometry, instead of the alloy ones?

[ThunderDragonCy 8380]

8 hours ago, Wheel_Nut said:

I got a set of those XV-01 alloy bellcranks in preparation for my 2WD truck project.   I think they are a bit shorter than the one you made for the earlier edition Ultra G with blue suspension arms.  I wonder if there may be a compromise in precision for the servo linkage.  Do you see any benefit in designing a custom bellcrank with revised geometry, instead of the alloy ones?

I designed the custom single bell crank because at the time i couldn't figure out how to make a double one work. Having the xv01 parts in my spares box meant i tried them out this time and i was surprised how easily they dropped in. That said the only advantage it has is slightly better bump steer.

[ThunderDragonCy 8380]

More detail bits. Firstly I got the Schumacher front arm inner pins, and the only way they are retained is by a plate that screw across the front. Of themselves they don't have any screw threads or e-clip grooves. Due to the space I have I couldn't put a front retaining plate on, but now I have the kit I measured up the tub and modelled a little more of it around the area. There is a front version surface of the tub just ahead of the arms, and the pins are a bit longer than they need to be so they'll still hold the arm on even if they move a couple of mm, so I moved the arms up on the mounting block a little so I can still install them, but if the pin works loose and moves it will stop against the tub before it can lose an arm. The pin in the blue part. The tub is the light purple-ish bit. The arm is red

Due to that small move of the arm, I had to go around all the camber links and shock tower again to make sure everything worked properly. Needed a couple of tweaks, mainly to the tower, but I also worked out I can now include a cross brace and still get the body through, so that's good.

At the rear, I have been a little concerned I was just relying on the mounting of the carbon base plate to hold the car together. Again, now I have a bare tub to look at and measure, I figured out an optional transmission brace which hangs down from the old resistor mounting points. It's the tan coloured part. It's not going to be super stiff, but I figured another attachment to the tub can't hurt.

 

[ThunderDragonCy 8380]

Read m'colleague @Wheel_Nut Hornet build thread and took a couple of bits of inspiration for some things that had been bothering me.

Firstly, through all my Ultra buggy builds i have wanted to figure out a way of reinforcing the front of the around the steering aperture. Ultra G cracked a tub there and i have been trying to figure out something inside. @Wheel_Nut simply put a plate on yhe underside. With a smaller steering aperture. Easy! Brilliant!

The other thing he did was use an M07 steering set. Whilst i am not going to cgange to that, i am designing and 3d printing the steering bar, and the M07 has the steering arm balls rotated 90 deg to the link pivots allowing more free movement. Mine had them underneath and i was worried they would pop off at full bottom out. 

The pic above is from underneath with the arm block removed so you can see the plate (carbon weave) and steering link (pink). The link isn't an m07 one, i just designed another link in the same style. Everything looks like it clears and both should work great. 

I like that the time it's taking for my parts to arrive is allowing space to make these little tweaks and improvements. Getting excited for how it will come together.

[Wheel_Nut 376]

Nice to see the CAD 3D model.  I definitely approve of the chassis reinforcement.  I wondering how much caster angle is used compared to the Ultra G.  Are all of the parts already on order?

[ThunderDragonCy 8380]

@Wheel_Nut Thanks. This has 25 deg kick up for the arms and 0 deg c-hubs. This seems fairly standard 2wd setup. Most cars (including the TRF) have 25 deg kickup and optional 5 deg caster c hubs for bumpy tracks. I tried both on my TRF201 and TRF211 and preferred 25 so i am going with that to start with. I can always do some more c-hubs with 5 deg caster if i want them.

Ultra G was done when i was less experienced with 3d CAD so has about 10 deg kickup and 5 deg caster on the c-hubs. I tried getting more on Ultra Hornet but the really wide fitting of the DT03 arms meant they hit the tub before bottom out on the shock, so that has a littke more than Ultra G, but not much. The slight issue with both the other buggies was keeping the stock from shock tower. Its tight anyway, and more kickup brings the arm closer to the tower leaving less room for the shock, or less tgan ideal geometry. On Ultra Hornet the shocks bottom out before the tub hits the floor which isn't ideal.

[ThunderDragonCy 8380]

Oh, and to answer your other question, none of the 3d printed or carbon parts are ordered yet. I gave most of the bought in parts already. I am waiting on a shipment from Plaza Japan so i can build my mashup front short shocks and confirm all dimensions and fit up by measurement of the real shock, then i can finalise the front tower and at that point i will order everything i have designed. I can start the tub build, shell and shocks whilst waiting for those.

[Wheel_Nut 376]

The 25 degree angle looks a lot more contemporary, but the Ultra G seemed already quite decent for what it was, judging from the video in the other thread.  I think these Grasshopper style cars have a forward C.o.G compared to other buggies, so it probably affects the handling balance.  Anyway it will be interesting to see how well these changes translate to on-track performance.

[ThunderDragonCy 8380]

@Wheel_Nut Ultra G runs great, but part of the fun here is seeing how far i can push this silly idea using a gh2 tub. Have to say, shout out to the Schumacher LD3 manual. Lovely, detailed setup explanation and suggestions at the end. Learned a lot.