Thunders Grasshopper EVO Project

[ThunderDragonCy]

Threw an esc in and gave it a run in the street. Drives really nice. 380 is quite noisy and got a bit warm in just a few minutes, so might still be a bit tight on the mesh. Have to say I liked the slow and steady 380 vibe! 

Everything moves quite well, but the front suspension was running very low. It's also quite slow on the damping. As I haven't got any lighter oil I will get some shafts for them to put the proper pistons in. 

Although running quite low at the front, it did bottom out the tub just before the shocks, which is good. However I thought it would be worth trying to lift it. Ultra G and Ultra Hornet both bottom their shocks before the tub, which whilst not ideal, does give nice ride height and handling.

I popped the long eyelets on to see if they fitted and my new arms have enough clearance to make them work. They look good and the tub now sits roughly level after being dropped from a couple of inches so I think I will try this next. 

Need to swipe some double sided tape from work to stick all the electrics down and it will be good for a proper run. Might throw in the 540 silver can to see if the trans whines in the same way as the 380.

[ThunderDragonCy]

Interesting possibility if it ru s nice at the higher front ride height is that I could do some revised front arms eventually with less offset to the damper mounts and go back to the short eyelet. That would be neat.

[Wheel_Nut]

I don’t mind the offset shape of the arms.  It has a similar effect to leaning-in the shocks, to give more suspension travel and create a progressive spring rate.

The spring geometry with the offset shock position looks similar to the Grasshopper 2.  I wonder how close it actually is, and whether the maximum wheel travel is similar.

[MadAnt]

This thing is looking fantastic. 

Also, for raising the ride height, maybe just the C hubs need to be offest a bit. This way it keeps the control arm angles closer to level which may be better for handling and ground clearance.

[Andreas W]

That turned out as a proper Grasshopper Evo. The proportions are now spot on. Looking forward to read your impressions after you have driven it more.

This is something I would liked to build out of my 2nd Grasshopper kit. I am already looking for a  2nd hand, cheap Dragon. 

[ThunderDragonCy]

A quick spin in the street with the 540 motor and highfront end. 

On the motors, its way quieter and smoother than the 380 so the 380 mount still needs another revision.

On the suspension, ground clearance and bump performance much better, but front grip waaaaaay lower. Lots of understeer. There will be a compromise somewhere. I suspect softer front damping and a little lower ride height will be the thing. Need try some other eyelets on the end of the shock to try and get somewhere between the short and long CVA eyelets. 

[Wheel_Nut]

Grasshopper front tyres often give understeer.  The high front roll centre is part of the equation too.  Stock swing arms would have an even higher roll centre.

[ThunderDragonCy]

Tweaked the shocks. Replaced the cva eyelets with short open trf adjusters, which grip the thread enough that I could wind them out 4mm and have them stay there. Car sits nice now and runs well enough in the street.

I decided to charge up a battery and head up to the park after tea for a proper run. As I was slightly skeptical of the tyres I packed the 2.2" JC Racing Wild One style fronts with cut staggers off Ultra G, and the Grasshopper 2 rear wheels and tyres. 

The grass was pretty short, but the kit wheels and tyres, front particularly, we're pretty bad. Rears were OK, but fronts just had nothing. 

After a bit of razzin about I decided to switch the fronts. Suddenly the steering was pin sharp and it was the rears that couldn't live with the grip! Swapped on the Grasshopper 2 wheels and tamiya pin spikes from the Saint Dragon kit. Brilliant! Loads of rear grip, nice front, lovely!

 

 

Ran in the grass for ages. I haven't run a silvercan for years, but with the 15t pinion and a punchy lipo it was really nice. Wouldn't want much more. Even more interested to get the 380 running now, especially a Sport Tuned for Club 380 racing.

So, whilst I really REALLY wanted to run with the kit Grasshopper wheels, the fronts particularly really are rubbish. Are there any 1.5" fronts from BITD that have some spikes?

Otherwise, although it's not the look I want, something that I can put a rib/spike on would seem to be the solution. Wild One fronts would be the obvious choice and are a touch smaller than the JC I ran tonight. I want that vintage small wheel look, but I also want to enjoy driving the car. 

Really pleased with how it handles though. It seems to be fundamentally a good buggy.

Any other 1.9" or small front wheel suggestions that have some actual grip gratefully received

[Wheel_Nut]

I think the Grasshopper 2 front tires would balance much better with the paddle tires on the rear.  Particularly on dirt, the harder ribs have more bite into the surface.

[MadAnt]

19 hours ago, ThunderDragonCy said:

Any other 1.9" or small front wheel suggestions that have some actual grip gratefully received

That's awesome, you have been making great progress on this project.👍

I do have a 2.2 size wheel recommendation. The Kyosho Turbo Scorpion five spoke wheels will give it that classic look while letting you be able to use modern or easier to obtain tires.

I'm using those wheels now on my Hornet EVO, but with different tires now than what you see in the photo. The offset is a little wider, but it still looks pretty good.

[ThunderDragonCy]

Thanks @MadAnt I appreciate that. Those scorpion wheels are cool, but I have plenty of 2.2 options on my other Ultras. I want this to have a proper old school sensibility. Will keep looking.

[Grumpy pants]

The best SRB combo is reputedly Rough Rider front wheels/tyres and Super Champ wheels/tyres on the rear.  

The FAV & Buggy Champ uses the same fronts wheels/tyre combo @ 1.7. 

Hornet & Fighting Buggy use the same rear wheels/tyre combo. 
 

[Andreas W]

If you 3D print an adapter for the rear wheels you can run white Tomahawk wheels with ditto tyres.  The soft fronts should give plenty of bite while still keeping the old school looks. M tyres at the rear are probably grippy enough for you. Modelsport normally has all this in stock.

 

Here my not so sophisticated Grasshornet with Scorpion wheels and the mentioned rear tyres. (The fronts are Schumacher Cut Stagger LP, which work good but wouldn't cut it for you in the looks departement).

[ThunderDragonCy]

After contacting Schumacher about the modern J Concepts tyres that would fit Grasshopper2 fronts, and found they would be special order from USA, I bit the bullet and ordered up some Wild One fronts and rib/spikes. I just can't believe absolutely no one makes something better than the kit tyres in 1.5". 

[Wheel_Nut]

Are the grasshopper 2 rear tyres the best vintage option or do you have something else in mind?

[ThunderDragonCy]

2 hours ago, Wheel_Nut said:

Are the grasshopper 2 rear tyres the best vintage option or do you have something else in mind?

They seem to work great on grass, so I am going to leave them on. Its not about cutting edge performance, just something that is enjoyable. 

[ThunderDragonCy]

I suppose some Hornet rear tyres would be good too, but I had these in the Saint Dragon kit

[Grumpy pants]

3 hours ago, ThunderDragonCy said:

I suppose some Hornet rear tyres would be good too, but I had these in the Saint Dragon kit

That’s what I’m going for, not based on driving/handling experience tbf, just the hope of a bit more grip in the dirt and short grass.

 

[Andreas W]

I simply love this conversion. I have been playing with the thought of building a hommage to my brothers Hornet from back then. I have a complete second Grasshopper kit and all part needed to build a Hornet out of it, but I don't feel the need for another solid axle RC. Which of the Dragons is the best donor for this conversion? More or less at every time one of the lesser Dragons are sold cheaper here. ATM the Thunder Shot is the cheapest with the Saint Dragon on second. Does the Fire Dragon come with proper damper pistons? My cheapo Thunder Dragon had that. I am not keen on the nailhead pistons.

[ThunderDragonCy]

17 minutes ago, Andreas W said:

I simply love this conversion. I have been playing with the thought of building a hommage to my brothers Hornet from back then. I have a complete second Grasshopper kit and all part needed to build a Hornet out of it, but I don't feel the need for another solid axle RC. Which of the Dragons is the best donor for this conversion? More or less at every time one of the lesser Dragons are sold cheaper here. ATM the Thunder Shot is the cheapest with the Saint Dragon on second. Does the Fire Dragon come with proper damper pistons? My cheapo Thunder Dragon had that. I am not keen on the nailhead pistons.

That's fantastic @Andreas W You need either the Saint Dragon, Fire Dragon or Terra Scorcher because they are the only ones with four dampers. You could definitely do something similar without using the Hornet EVO axles and kit wheels with the Dragon rear suspension and driveshafts. Even use the Dragon wheels on the rear. PM me for the mounting block for Dragon arms on the front like Ultra G. Or I can look at sourcing all the 3d printed parts I used here for you. I priced up all those parts at about £75. Just let me know. Keen to help someone else build one.

[ThunderDragonCy]

Parts list for those interested.

Grasshopper kit (or hornet and then the Grasshopper parts tree with the solid swing axle mounts)

From the kit you need:

Tub

Body

Driver

Grasshopper swing axle mounts 

battery door

A10 arm retainer

MSC mounts (cut to lower the servo as per Grahho post above)

Bumper

Front knuckles

Screwpins for front knuckles

Wheels and tyres should you so wish

Wheel nuts

CTE (that's my stuff):

Front arms

C hubs

Steering base plate

Camber link mount

Steering master arm

Steering slave arm

Steering wiper bar

Thundershot trans bobbin extenders for Grasshopper axle mounts

Upper trans mount

Low shock tower

Short rear arms left and right

Right uprights

Thundershot chassis parts (probably best to get a whole kit and sell the unused bits):

A parts for rear trans case

Gear parts bag for rear diff, spur gear, outdrives, bevels, layshaft, 2.6mm screws for diff and trans cover

Motor mount

Brass tubes for motor mount screws

0.8mod pinion of your choice (for motor around 27-23t I would suggest the steel 17t tamiya pinion)

If you have bought a whole kit then B8 rear arm mount. Otherwise if buying parts I can do a 3D printed one

If you don't want to use suspension shafts then the screwpins from the thundershot chassis kit for rear inner arm pivots, outer arm pivots both ends.

If you don't mind JIS screws, use the kit m3x6 for the motor and m3x22 for motor mount.

Random ebay bits:

HSP 61mm dogbones https://ebay.us/m/FCmgFX

2 x 100mm long 3mm stainless rod to reinforce Front arms - cut to length once pressed into arms https://ebay.us/m/QWUkcC

Other Tamiya Parts:

Hornet evo rear axles

If using suspension shafts 

2 x 48.5mm for rear inner arms

4 x 33.3mm for outer arms front and rear

13 x 5mm ball nuts (inner and outer camber link rear, out camber link on c hub front, Steering wiper front, upper rear shock tower mount rear)

8 x 5mm ball screws (inner camber link front, front knuckles, steering arm and servo saver, rear arm shock mounts)

14 x 5mm open adjusters. Any will do but suggest the long open adjusters 51283 or 54869

Turnbuckles depend a bit on adjusters, but 4 x 3x32mm front from and rear camber links, and 2 x 3x42 for steering arms should work. You can always just cut m3 rod instead. 3x65 for servo steering link or again just cut a threaded rod.

Hi torque servo saver or similar long servo arm

2 x cva mini shocks front, short eyelet, cut eyelet from the top (see above). Drill out, push m3x20 button head screw through. Tighten down with m3 nut. 3 x tamiya o rings, pass through shock tower, 1 x tamiya o-ring, m3 nyloc nut tightened until flush with end of screw.

2 x 50591 ball collar for front shock arm ends.

2 x cva short shocks rear with 9808074 41.5 piston rods, short eyelets

Assorted other parts:

10x 1150 bearings

2 x 850 bearings

4x 830 bearings (8 x 3 x 3)

4 x 730 flanged bearings 

2x m3x20 countersink screws + 3mm x 1mm thick spacer for steering arms

2x m3x25 cap head screws for steering arms to wiper

2x m3x25 cap head screw for c hub camber link balls

2x m3x25 cap head screws for front arm shock mounts

4x m3x10 cap head screws for steering wiper balls and rear inner camber link balls

4x M3 x 16 cap head screws for rear outer camber link balls and upper shock mounts

2 x m3x16 screws plus m3 nuts for steering base plate mount

3 x m3x16 countersink screws plus m3 nyloc for camber link plate mount.

4 x m3x10 cap head screws for upper trans mounts

Assorted screws from kits for mounts shock towers and trans mounts and nerd bars etc.

I think that is it!

[ThunderDragonCy]

Additional: If you want to do the build at a lower cost and are not bothered about using the kit rear wheels, as mentioned above, bud the rear trans with all Thundershot chassis parts and wheels and that will have a nice width. If you do that you can use the B12 narrow rear shock tower and cut the top off and that should clear the Grasshopper shell. Then just setup the rear shocks ad per the Thundershot/Thunder Dragon manuals.

I can sort you a front arm mount for Thundershot arms like Ultra G and some c hubs to use the Grasshopper knuckles and front wheels. You can use the regular servo position too if you aren't fussed about linkage steering. I would suggest cutting the servo aperture anyway and centring the servo as much as you can, then use the turnbuckles from the DT02 set (can't remember the lengths) or m3 threaded rod again cut to length. You would just need the camber link plate 

[ruebiracer]

Such a cool car @ThunderDragonCy, looks absolutely fabulous now. You´ll sort the tires out, I´m pretty sure.

[ThunderDragonCy]

Was thinking about this a little more last night, and wondering if a 3d printed gearcase that used the Grasshopper internals, but broadly kept the same layout as this car might be more cost effective. You really do end up not using a huge amount of a Thundershot series kit, but to buy the parts on their own is quite a lot. Got thinking that even if the gearcase was 50 pounds or so it would still be cheaper than a TS kit. Only thing with that is having to do do the hacksaw mod on grasshopper rear axles that seems to be a feature of all the other conversions. I always thought that was a bit janky, but actually it's probably not that hard when I think about it. 

Anyone got any thoughts on this?

[Wheel_Nut]

The Grasshopper stock gear set is not the greatest for this application IMO.  The drive shaft out-drives may be hard to source, and the really janky part is using 4x bearings to support the diff (unless you find a smart way that only requires 2x bearings).  The other disappointment is the open gear diff.  It would be better to use a stronger version of the DF-01 that allows a ball diff.  Alternatively the MIP ball diff and Monster beetle counter gear could be an option.