Grasshopper 2 Ultra G Evo Black Edition

[ThunderDragonCy 8115]

New 3D vendor is very fast!

New case install. All bores nice and tight and feels really smooth. You can see the extra clamp boss in the middle there. Also changed the rear block mount. It's 1mm higher so now has no anti-squat, but I have a spacer printed that i can put the anti-squat back in if needs be.

[BuggyDad 5320]

2 hours ago, ThunderDragonCy said:

New 3D vendor is very fast!

New case install. All bores nice and tight and feels really smooth. You can see the extra clamp boss in the middle there. Also changed the rear block mount. It's 1mm higher so now has no anti-squat, but I have a spacer printed that i can put the anti-squat back in if needs be.

Nice! I might try to find my way to a similar camber link mount solution where I've used a BBX gearbox. 

[ThunderDragonCy 8115]

50 minutes ago, BuggyDad said:

Nice! I might try to find my way to a similar camber link mount solution where I've used a BBX gearbox. 

It's basically a copy of the Schumacher arrangement, but it seems to do everything i need it to

[Wheel_Nut 365]

Removing the anti-squat may help with traction.  Sounds good to me.  Do you have a gear cover to fit on?

[ThunderDragonCy 8115]

8 hours ago, Wheel_Nut said:

Removing the anti-squat may help with traction.  Sounds good to me.  Do you have a gear cover to fit on?

That's what i hope. All my other mashup "Ultra" buggies don't have it and they noticeably squat under power, but i think that's a good thing. 

I do have a spur cover, but i have struggled with tapping threads into the motor plate in order to mount it

[ThunderDragonCy 8115]

FINALLY managed to tap the stainless steel plate. Was getting nowhere with trad taps again, when in desperation i tried my Tamiya Thread Forming tool. And it only worked! Spur cover.....ENGAGE!

Psyched out of my tiny mind to run this at the track.

[Wheel_Nut 365]

I think reducing the anti-squat must improve compliance and grip.   I suspect it may have a slightly forward C.o.G, so it may benefit from higher front spring rate.   I look forward to the news of your track test.

[ThunderDragonCy 8115]

The long awaited first proper run of Ultra G EVO didn't end well. Ran at Tamiya Junkies today, on the indoor track to see where i was. Lots of understeer, and then failure on first hit on the shipping rope track marker.

Broken on the 3d printed arm mount. Never broke one before on an Ultra buggy, but due to the Schumacher arms the boss is much shorter, so much less material. Very much back to the drawing board. Needs stronger front arm mount and much more front end. 

[BuggyDad 5320]

Just now, ThunderDragonCy said:

The long awaited first proper run of Ultra G EVO didn't end well. Ran at Tamiya Junkies today, on the indoor track to see where i was. Lots of understeer, and then failure on first hit on the shipping rope track marker.

Broken on the 3d printed arm mount. Never broke one before on an Ultra buggy, but due to the Schumacher arms the boss is much shorter, so much less material. Very much back to the drawing board. Needs stronger front arm mount and much more front end. 

Sad face. 😢

Lovely to catch up today and see so many other buggies running well though. That rope can be unforgiving because wheels/bits catch it rather than sliding, I think. I came unstuck in a similar way. 

[Wheel_Nut 365]

Sorry to see your mishap on the track.   I wonder if the design of the front suspension mount can be changed to add reinforcement for the hinge pins ahead of the suspension arms.   I also thought about bolting the suspension mount to the carbon fibre plate.   It would become more rigid, but possibly less flexible and prone to breaking.  That aspect needs some thought.   I made a crude 2-D picture to show my idea, although I figure you might have thought of this already.  The kick-back could be reduced to 20 degrees if there is not enough space.

[ThunderDragonCy 8115]

Thanks for the suggestions. I have designed a new version with tabs boths sides of the arms to hopefully improve things.

[ThunderDragonCy 8115]

Ultra G Evo is back together. Despite having had the parts for weeks, I have been a bit "off" RC. I think it's because work keeps getting in the way of going to track meets, so I am not motivated to fix my cars. Possibly also the fact that first run handling was really poor, so I a bit annoyed it wasn't better. Anyway, here it is

And here is the reinforced front arm mount

Extra tabs in front and behind the arms. Ditched the Schumacher pins for some 1/8" ground rod off eBay, cut to length with my cable cutters. Not subtle, but it fits much more snuggly in the parts. That 3.2mm drill must have just opened the hole out too much in the first version. FYI 1/8" is 3.175mm. 

Due to the massive understeer it was suffering on the first run I took the opportunity to flip the front arms so they are in short wheelbase position. It's only 3 or 4mm, but I think it will help. I think the stance is nicer if nothing else. I have also lowered the roll centre at the rear, which should also help. I noticed on Ultra Hornet the top camber links are angled down towards the middle quite a lot (which lowers the roll centre, and in theory improves steering), so I have gone in that direction here too. 

Still concerned the damping is a bit much with my trick pistons, but at least I can pop some 300cst oil in them at the track if I feel the need. 

No idea when I might run this, but nice to get it done.

[Grumpy pants 5178]

Impressive ⬆️ 👍

Looks great your GH, nice stance too 👏

[ThunderDragonCy 8115]

Well, getting this fixed up got me looking for opportunities. I was pretty much passing the club on my way to meet my family for lunch today, so I set off an hour earlier to give this a go

I had time before I left to put 300 oil in the rear dampers (down from 400) and I also swiped the similar length (but much softer damped) shocks off Ultra Hornet as well. 

First things first: It ran really nicely! Balance was a little understeer, but generally nice. Certainly WAY better than that first run. Had a really lovely feel, and there is definitely a great buggy under there somewhere. 

It was diffing out a bit and spinning on corner exits a little. Not much, but enough to be careful on bumps with the throttle. I swapped the softer dampers on and traction was better. I think I definitely need to open out the holes in the pistons in the dampers and soften them off a bit. Not too much though. It absorbed landings nicely and was generally good. Might try some slightly heavier oil in the rear diff too. 

I also played with the slipper and got that set nicely. It was pretty much locked to start with!

Encouraging, and so relieved it's nice! 

 

[ThunderDragonCy 8115]

Finally found my pin vise set! This pushed me into stripping the rear end down and getting oily.

Insides of the trans all look good, but the diff itself was running quite rough. I have never used the full steel internals in one of these ta06 diffs. I always put the steel cross shafts in but used the plastic bevel gears thinking i would replace them when worn. Even on my trf211 or ff03 they never did! The steel bevels in this are noticeably heavy and run quite rough. Need to keep an eye on it. They appear properly shimmed and adjusted.

Anyway, the limited running i have done has me wondering if i need some more diff action. If the car is sliding out of a corner it tends to spin up a wheel and loop rather than driving forward through the slide. I had 3000 oil in there, which is pretty usual for a buggy gear diff, but it felt very open in action in my hands. I pulled it out and put 10k oil in simply because that's what i had next step up. Doesn't feel too stiff. Hope that it's good. 

One side note: Despite being efficient in terms of design and doubling up certain bolts in the trans to do two jobs at the same time, it is really quite tricky to take apart and put back together again. Something to learn for the next one.

Now the trans is all buttoned up i pulled the dampers apart. If you haven't read the rest of this/can't remember, i got some onroad SSBB 11mm diameter pistons for the cva shocks, with 4x1mm holes. I did some maths comparing to small and big bore buggy damper pistons and opened up two of the holes in each piston to 1.2mm.

Now i have found the damping a bit much having run the buggy, i simply opened out the other 1mm holes to 1.2mm. So, i have 4 x 1.2mm holes front and rear.

As a comparison, the buggy big bore (12mm piston, not 11mm as here) uses 2 x 1.7mm holes front. That's 4.54mm2 of damper port area. 4 x 1.2mm holes is 4.52mm2 port area. But in the smaller 11mm damper this should theoretically be softer as there is more "hole" than "piston" in the 11mm vs 12mm. It really doesn't feel that way. 

 

I rebuilt them with 450 oil front expecting much softer feel, and they felt good. Not fast or under damped, just good. I rebuilt the rears and put 400 oil in and with the springs i have running they still felt a bit slow and "heavy" action. So, i immediately emptied them and put 300 back in like last time out running. Feel good now. Lively, but still damped. Hopefully they will be good and get me some more traction. 

Oh, i also added a spacer above the spring cup to limit travel as i relaised when bebuilding the rears this was possible

Looking forward to testing the new setup. Only thing i can think of that these dampers feel so heavily damped for similar hole sizes to aeration dampers is that the SSBB pistons must fit more closely in the bore, with less gap for oil around edges.

Despite the faff these do feel great and still way cheaper than big bores even with buying the extra internals.

 

 

[ThunderDragonCy 8115]

Additional: All this oversteer behaviour got me wondering about the front of the car. Buggies tend to roll oversteer if the front is too soft in roll. I checked and realised i had the other (lower) inner camber link setting available on my front tower. That will raise the front roll centre and reduce roll. Changed too many settings at once probably, but wanted to tinker

[Wheel_Nut 365]

Interesting comment about roll centre.  It made me think that ride height change is likely to have a bigger effect on roll centre than a small change in geometry.  Can you lower the rear ride height to improve rear grip?
 

Some of the earlier photos you posted were confusing to me, since it seems like the battery wasn’t fitted.   That causes a big change in ride height, and perhaps more so at the front than the rear.

[ThunderDragonCy 8115]

54 minutes ago, Wheel_Nut said:

Interesting comment about roll centre.  It made me think that ride height change is likely to have a bigger effect on roll centre than a small change in geometry.  Can you lower the rear ride height to improve rear grip?
 

Some of the earlier photos you posted were confusing to me, since it seems like the battery wasn’t fitted.   That causes a big change in ride height, and perhaps more so at the front than the rear.

Ride height definitely has a strong effect, but with the battery on board it sits at about 22mm and fairly level. I don't think I want it much lower as it's already quite hard to find grass short enough to run it, and the astro track I occasionally get to is quite bumpy. I could quite easily try softer rear springs and use preload clips to play around with the ride. I want to see how all the changes I have made now work first though. I have a feeling the diff will be quite helpful, but it will be good to know for sure.

[ThunderDragonCy 8115]

Not going to get to the track for a while so i decided to put the road tyres on and have a play in the street to see what my changes have done. Firstly, after being a bit disappointed with the speed i got a 25t pinion, up from from the 23t. This drops the FDR from 8.7 to 8. It's definitely faster and still seems to accelerate well, but also tops out quite quickly. I do wonder if it would work with even lower fdr. What are other people running a Superstock with?

 

I gave it a run and still was a little wayward under power, but not quite as much. It also got a bit kicked at the rear on a chunky drain cover, so maybe the 300 oil at the back wasn't enough?

As it was on tarmac i noticed than when it was fishtailing under power one of the front wheels was coming up. So that got me thinking that possibly it was too soft at the rear. When you are looking for traction you tend to soften off the rear suspension so it keeps the wheels more in contact with the ground. However there is a crossover point where too soft allows the weight to transfer too much and it rolls too much too. 

I tried some stiffer springs from the yeah racing set. Possibly too stiff, but although they didn't cure the oversteer, it definitely contained the weight better. Something to keep in mind i think.

I also installed the shim to introduce some anti-squat

This also gave a noticeable difference on power. Not sure if good or bad! 

 

[Grumpy pants 5178]

Very clever! 

Well above my pay grade 😂

[ThunderDragonCy 8115]

More tinkering today. Didn't take many photos, but did snap a pic of the tub mod i did so i can run a shorty a little rearwards as well as slammed all the way forwards

 

6.5mm drill wiggled about a bit until the slots are big enough for the plugs.

In search of better handling, i moved the upper outside (hub end) camber link pins inboards on the rear to shorten the link and raise the rear roll centre a little more. Also put 400 oil in the rear shocks to make them less bouncy. Not sure roll centre wrked much, but rear was more settled on bumps.

Started looking at ride height and droop and it seem it's running quite high at the front with loads of droop. More than the rear. I must have got my sums or measurements wrong on the cad. 

I used my trusty 2x lego bricks per end with no springs fitted setup method to measure the shock length at 21mm ride height. Then i lifted it up to full droop/shock extension. Rear was about right to CAD at 36mm ground clearance at full extension. For reference in the design i used Ultra Hornet which is about the same. 

Front was way over 40mm! I worked out i needed about 3mm shorter. Front shock as built is 82mm. With a 3mm cva spacer inside (and 550wt oil back in) it's 79mm, which gives about 34mm droop. I now don't really have any springs that fit so i am going to buy a couple of the firmer Core RC big bore fronts and see where i get to. 

[Wheel_Nut 365]

It seems a really good idea to get the front springs sorted.  The geometry changes so much if the ride height setting is off.     Hopefully some shorter front springs allow better geometry so you don’t compromise front grip, even though the spring rate is higher.   In other words, It could be one way to improve grip at the rear of the car without any compromise (particularly in a low traction situation).  Please post pics again when it’s updated, with the battery fitted of course.

[ThunderDragonCy 8115]

The springs arrived. I went for 2.6lb rear and 2.8lb front.

Front springs needed a thick spacer to take up slack and a medium spacer to even up the ride height with the rear. This is about 19mm with shorty battery pushed all the way forward. 

Will give it a run at the weekend.

[Wheel_Nut 365]

Looks good.   Maybe you can try the rear battery position too.

[ThunderDragonCy 8115]

3 hours ago, Wheel_Nut said:

Looks good.   Maybe you can try the rear battery position too.

I definitely will when i give it a run