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ThunderDragonCy

Grasshopper 2 Ultra G - Independent Suspension All Round

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This project idea has been rolling around in my head for a couple of months. I love Grasshopper 2 bodies, but never been a huge fan of the buggy underneath, hence my grafting a body onto my DT03. I also love Thunder Dragon's too, and after reading a few things around the net a plan began to form to build Ultra G: Super G's big brother. My original plan was to flouro spray some modern 2.2" wheels to get the Super G look, but then this turned up on Facebook. What can I say? I'm a sucker for the fluoro wheels and the fact it came with a new shell and decals made it a bit of a bargain overall.

Ultra G

The Thunder Dragon rear gearbox and suspension wasn't with the Super G, I just put it in the photo to show you what I'm thinking. I put the gearbox together from spares and some help from fellow TCers. Thanks chaps. The chassis on the buggy is brand new, and the seller supplied the cracked original. Was about to fix it when I noticed the body clip turrets are also mangled so I think it's in the recycling bin for that fella. I have skipped ahead a bit because I pulled all the very tatty original decals off the original shell at lunchtime and gave it a clean up. If anyone has a beat up but serviceable GH2/Super Hornet/Rising Fighter tub and battery door PM me. If I had those I can make a whole GH2 out of the leftovers!

So here's the big idea - Ultra G is Super G's more capable, more developed brother. I'm going to replace the GH2 rear end, motor and gearbox with the Thunder Dragon transmission and suspension. That's the rear suspension sorted. The Thunder rear end still mounts through side plates a la Hot Shot series, so I plan to make some spacers and drill the GH2 gearbox sliders on each side to catch the bottom mounting hole with some long screws, and then make some short rods and some ball ends to mount from the top gearbox mount to the GH2 top shock mount. That might allow some adjustment of the gearbox angle, to tweak anti-squat, which might be fun. That's the idea anyway. We'll see. 

For the front I've ordered my 4-bar conversion piece from Shapeways and have some DT03 c-hubs on their way courtesy of @ALEXKYRIAK (thanks dude!), and I have some DT03 uprights spare. Question here is whether I get the DT03 front wishbones like I've done on my Rising Fighter, or do I keep it more vintage? Thunder Dragon arms would also fit and are a little shorter which is more in keeping with the idea of the buggy and era to which the chassis belongs. With some shims the C-hubs will fit the other end no problem. What do you think? 

Wheels will obviously be the Super G wheels, but with some Schumacher CAT Blocks on the rear, and something suitable for the front. Haven't decided yet. 

Bodyshell-wise, after a series of loud coloured GH2 bodies on my other buggy, I'm going a little more trad this time. It will be white, but I'm going to get a set of the Grasshopper 2 Jnr Dress Up decals I sorted out through MCI. I'm thinking Version 2 decals, but go neon green as that stock green is a little wishy washy for my tastes. Or maybe blue instead of green for a blue/red decal scheme like the original GH2? Again, would be good to here your thoughts.

gh2 v2gh2 dress up

As I wasn't expecting to pick up a Super G I had already sourced some modern black CVA shocks for this. Now I'm torn. The CVA2 is better than the originals - you can mount them on ball ends for a start which you can't on the old yellow shocks - but the look would be great with the original shocks. Not sure. This is going to be a runner so it does need to drive nice. 

Anyway, the adventure begins.....

 

 

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This is intriguing! I am almost as excited as you are for the start of this project.

About all I can contribute is my support for the green decals, but only because blue/red in that style makes me think of the Super Dragon instead...

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Definitely following this one Cy, looks very interesting. I like your adventurous spirit of mixing and matching. I understand your love for the Grasshoppers, I too like the shells and character of the Grasshoppers, I keep meaning to get around to getting hold of a Grasshopper (and poss a GH2) but the kit list is long enough as it is. Interesting mix of Thunder Dragon and the GH2.

I didn't really know anything about the Thunder Dragon, until my very recent refresher  via Google -  looks quite 70s/80s....! A definite nod to Giuseppe Nuccio Bertone methinks. Interesting to read that this car is apparently the next step up from the HotShot?

Also like the idea you're going for the more traditional colours. The white, red, and green are classics, immutable like British Racing Green or Ferrari Red.

Following.

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Cheers guys. @ALEXKYRIAK yes the Thundershot series chassis replaced the Hot Shot series after the Super Sabre (boomerang chassis) was released. It is a big refinement of that idea with modern length driveshafts, better transmission, MUCH better steering parts. Still had its foyballs though. The kinematics are ok but the DF01 is quite a step on and although the linkage steering is much better from a bumpsteer and consistency point of view the maximum steering angle is rubbish. That is all a bit beside the point for this build though!

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So a bit ******* about, but this is a build thread, so I'll post build pics. This is the Thundershot rear gearbox I built on Sunday:

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Gear cases from a fellow TCers, diff casing and outdrives from the spares box, new metal internals. Make a note at this point to remember to install the metal washers you just bought especially for this build behind the diff gear shown. You wouldn't want the whole gearbox together when you realise you forgot them. Ahem.

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Filled about half full with the 300000 cst diff oil for some limited slip action. 

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Bearings, layshaft and spur gear installed. 

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No bevel gears or 4WD transmission installed as this is 2wd only this build. I did nearly forget to install the 1150 bearing the transmission housing though, because nothing else is in there. It supports the end of the layshaft so its important to pop that in. The end where the propshaft outdrive would exit is open, but I have a grommet from my mountain bike which looks like it might well be just the job to seal the hole.

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Arms from the spares box. As you can tell they have clearly seen better days, but we will go with them for now. I think they might be my original '88 Thunder Dragon kit arms. Uprights from another helpful TCer and bearings and screw pins from the bit box.

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Really baggy fit of arms to gearbox. There's a blue 2mm shim on the other side you can just see and a silver 1.5mm shim this side to take up the slop. Screwpins again, although I'll keep an eye on these as I have to replace them with shafts on the Thunder Dragon. That requires some modification though, so not keen for now.

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All done. Going with plastic top arms for now as I have brand new ones spare. Original narrow Thundershot/Dragon shock mount as again I have it spare. We'll see if I can get stiff enough springs for these to work. At least Ultra G is much lighter than my Thunder Dragon so it's got a chance. Waiting on some CVA V parts sprues so I can shorten the CVAs to fit these. The 94mm long short shocks are too long for this configuration.

Driveshafts are Yeah Racing Unis I had spare. I also have the option for a rear anti roll bar as I have the Terra Scorcher Rear Bar kit.

More to follow soon!

 

 

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Did a little bit more last night. Things got exciting with cutting bits up!

First things first. Finishing off the rear suspension I tried the shorter eyelets for 90mm shock length to fit to the original lower central mounting position but they were too long. Original Thunder Dragon shocks must have been 85mm. Not wanting to rebuild I tried the upper Long Shock position (for the now defunt 105mm shock length) and found them not far off. Popped the long eyelets back on for 94mm shock length and they fit perfectly with the arms on their top out stops. Goodness knows how you would fit shock 11mm longer unless they are built with internal spacers.

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Measuring up. The GH2 is 100.5mm across the outside of the sliders. The Thunder Dragon gearbox is 66mm wide.

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After measuring the depth of the slots I calculated that the spacers needed to be 15.5mm long. I mae them from 4mm OD brass tube. I Don't have a lathe so they are a bit rough.

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First fit up check. There's a slight problem!

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The motor hits the GH2 slider with transmission angled way down. No good. With the bottom gearbox mounts lined up with the bottom of the sliders and no motor the gearbox needs to be hard up against he chassis bulkhead. Quick wave of the hacksaw and all sorted.

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I drilled holes in the bottom radius of he slider using a circle mark from the moulding on the inside. It was tricky to stop the drill wandering on the smooth surface so i had to open out the holes a bit to give me some wiggle room. Hopefully it won't matter once the upper supports are in.

All assembled with M3 x 30 screws

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It seems fairly central and square but it is really hard to get everything lined up because I drilled the GH2 chassis mounts freehand. The closest everything sits gives a slight angle to the transmission which will give some anti squtmat, but hopefully it won't scupper the handling.

It doesn't feel massively solid with just these M3s in. Fingers crossed once the top mounting is in.

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Interesting project. I'm sure this is going to be one super nice runner when hitting the dirt! :)

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Is the diff sealed? I put oil in an unsealed diff, and it ended up everywhere but inside the diff. gooed up the whole tranny and even the outer case!

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15 minutes ago, _oliK said:

Is the diff sealed? I put oil in an unsealed diff, and it ended up everywhere but inside the diff. gooed up the whole tranny and even the outer case!

Not with an o ring, but the halves mate tightly and screw together. I use the same stuff in my dt03. A little bit comes out but not much.

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Some more this evening. The gearbox top fixings. First some ball ends in the top gearbox mount and GH2 top shock mount.

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Measured them and they are a little over 32mm centre to centre. I made up two very short arms with rod ends from the spare box and M3 threaded rod I have in stock. I used 17mm of threaded rod, and there's about 1.5mm gap between the ends of the collars. Pop them on to get a solid rear end:

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Feels fairly solid, but still a little concerned about the bottom mount. Will see how it goes when running, but I might run up some plastic spigots in CAD that would engage properly in the GH2 chassis slider and the Thunder Dragon transmission mount. I'll get them from Shapeways if something breaks.

So now it stalls a little bit as I'm still a couple of weeks away from my front end parts. I've ordered the decals for the shell, so I'll prep and paint that and the spare shell so that's ready for sale. Seeing as it was fixed up I chucked on some 12mm hex rear just to have a look. 

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Looks a little goofy as the springs are a little hard and there's no battery so it's all sitting topped out. Still, quite pleased with how it's going.

 

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6 hours ago, ThunderDragonCy said:

Not with an o ring, but the halves mate tightly and screw together. I use the same stuff in my dt03. A little bit comes out but not much.

What? Mine was screwed as tight as it gets, still caused a mess. Well, good luck. Maybe it works for you.

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This is shaping up very nicely. The proportions look like they're going to work, especially when it's all done up with better parts and a nice paint scheme.

The fixing of the rear to the chassis looks perhaps a little precarious, just imagining it under load landing a jump or something. Are there any ways to brace it further, or to triangulate the load paths? Can you get a solid shaft somehow between the two ball-studs, and then use that to brace off at the top edge? Can you get a second fixing at the front bottom edge somehow to counteract the pivoting that this might undergo under load given that it's effectively an axial element through here? Would be nice to see some more photos from various angles!

Loving this build, way off-piste and experimental.... this sort of thing is why there's that 'What is it about Tamiya?' thread....!  :)

 

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@ALEXKYRIAK The ball mounts at the top are actually pretty solid feeling. It's definitely the lower one I am concerned about. I couldn't drill out the thunder Dragon gearbox for a through shaft as you can't get a drill long enough. On the thunder Dragon it's only held with M3 screws but it sits in a recess in the chassis tub. That's why I think a plastic extender spigot which makes a better supported joint would be the one. I'll try and get some more photos. 

Another thing that helps is is that the front of the gearbox butts up against the chassis bulkhead so by making the top rods a touch short and flexing the chassis to fit them it's quite firmly installed.

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Little bit more today. Got my 4 bar conversion part from Shapeways and tried out Thunder Dragon arms. Looks like they will work so ordered a couple of sets so the buggy has new all round. Ordered a handful of M3 screws i need as well. Once i have these bits i should be able to finish it and get it running.

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Looks great, Thunder, am totally in awe of you designing your own bits, really impressed. :) I have had a go in Rhino myself on a few things, but haven't got it right enough to commit to a print.  

Do you think it would be possible to extend the plastic along the pin length somehow to minimise the need for packers and to minimise slop longitudinally at the base of the shock itself? It looks like there's a fair distance between the inside faces of the blue plastic, where that silver screw is. This arm looks similar to the DT03 lower front, and it has a similar characteristic, something I hope to be dialling out in my next DT03 build. Is the slide, at the bottom of the shock, a deliberate move by Tamiya do you think?

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@ALEXKYRIAK Thanks. I love designing things but it helps that its my day job. I have the right training and pro software to make it happen.

This was just a loose fit up. Shouldn't need any spacers with the correct length screws.

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Finally got around to some more work on Ultra G. Partly ill/busy/waiting for parts. Partly strangely gone cold on this. Not sure why, but i have parts now and an evening to crack on!

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New Thundershot wishbone front and rear. The used ones i had built the rear with were really for the bin. Very bent!

After my original cut brass tube spacers for the gearbox/chassis interface didn't inspire confidence, i knocked up some fitted plastic spacers on CAD and got them from Shapeways with a few other bit. The small end is 4mm diameter, sane as the GH2 gearbox pivot bar, which makes a better fit in the chassis ends. The other end slides over the end of the Thunder Dragon gearbox posts. 

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Worked really well. Solid!

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This is version 2 of my GH2/Rising Fighter/Super Hornet 4 bar front suspension conversion. All fits spot on and no need to drill the pivot holes either. Rwally pleased. If you search CTE RC on Shapeways you can buy them now too. 

Originally designed for the DT02/3 front wishbones, i wanted to keep the vintage feel and matching wishbones so fitted up some more Thundershot lower arms. As you can see they need a spacer, and also a tiny trim of the web to clear the pivot housing at the bumper end

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I threaded all the holes M3 to use up some spare stainless screws i have. Looks nice!

64mm CVAs installed in outermost position on wishbone. Installed with M3x20 screws, one if the brass fittings from the 50520 CVA set.

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Next part of the 4 bar conversion: Screw some ball ends into 2 servo posts, butt the post up against the rib on the shock tower and lines up with the top of the tub. Drill 2.5mm through the mounting hole and use a 10mm self tapper to secure.

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Once fixed, drill another 2.5mm hole through the post and tub (taking care to avoid the threaded section of the ball end) and screw another self tapper through. Solid!

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Didn't get any further, mainly because i think in the office clear out/tidy/change around the plastic DT03 c hubs @ALEXKYRIAK kindly sent me have gone missing. Quite annoyed! If anyone has a pair of plastic DT02/3 c hubs spare let me know!

Seems to be chugging along now and i have managed to acquire a set of the iconic Super G fluoro wheels. Also got some MCI Racing decals based on the Junior dress up decals i helped get done. Need to prep and paint the shell white.

Hope you like!

 

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Loving this build thread. I particularly like the front bar suspension conversion and the plastic spacers. Very interested to see how they perform for you. 

Would love to read more detail on how you design, conceive, measure, digitally model and then produce, if you ever have the time.  (At one point last year I was very interested in modelling up a car design but clearly it’s a very complex task - not like me to have aspirations way above my ability to deliver them!)

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DT03 c hubs turned up yesterday courtesy of very speedy Modelsport. Got a couple of hours this morning so after a hectic day at work yesterday i settled in for some calming tinkering Wooooooosaaaaaa.

Anyway....

Grafting a narrow 2wd c hub onto a 4wd wishbone was always going to require some spacing.

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Wishbone screwpin needed 4mm if packing. I used plastic M3 washers in the bit box. Pushed the wishbone forward to help front arm clearance. The Thunder Dragon wishbone is designed for the shock to run infront normally to avoid the driveshaft, but here it only fits in the centre. The ball screw for the front arm also needes spacing forward as well. Used a CVA shock large internal spacer and M3 x 20 screw.

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Rods ends and threaded shaft from the spares tray. Rather appropriately the shafts are Thunder Dragon steering arms, made redundant when i switched to DF03 uprights.

Did a first pass ESC install which fittef really nicely. Also found that i had been flexing the rear tower down with the upper gearbox mounts. The shell woukdn't fit i had moved so far! Reset with shell in place and ended up with 5mm spacing between rod end collars. To help stop this i put a strut brace between the resistor mount and the MSC mount. Can't do the other side because of the ESC

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Servo installed. Haven't got the right length threaded rod for steerkng arms

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Couldn't resist a dry fit up. Used the Pargustore adaptor for the Super G rear wheels.

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One thing i didn't apot kn my loose fit of the front end was how much narrow the track would be

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It is 250mm across outer edge if the rear wheels and 210mm across the fronts. On the one hand it does give a vintage Grasshopper2 stance, but not sure how it will handle. We shall see.....

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It lives! Got the steering sorted and bolted the battery door closed with m3 rod and nuts because i don't have the c14 parts. He's a lively little ******! Turns in really nicely, but back end is really slidey! Lots of wheelspin and spins with too much power. I suspect the ancient, hard oval blocks might gave something to do with it. Put soft springs on the rear and some 22.5wt oil in the front dampers so suspension seems in the game. Taking it to work for a bit of lunchtime grass running hopefully. Popped some spare Schumacher CAT blocks in my bag in case the oval blocks really are that terrible!

No pics or video. It was dark. More soon. Need to get the shell prepped and painted now the temperature is slightly higher. Quite chuffed!

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Read up a bit on what might be causing the lively rear and it seems that about 5 degrees of anti squat (induced by needing to angle the gearbox down to fit against the bulkhead) is excessive! Lots of anti squat causes the car to lose traction and spin out on the throttle - exactly what i was getting. Tried putting some CAT blocks on the rear to see if it was tyres, but no. Not that. 

To get the gearbox level i needed to move the bottom mounts away from the chassis, but the grasshopper2 gearbox mounts gave me limited options. My kids have a Rising Fighter with different gearbox mounts. I measured these and it turns out they are 5mm longer than the GH2 versions. A quick dry fit showed promise so i gave it a quick go

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I am painting the shell for this buggy right now so i popped my spare shell from my DT03 on

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Seemed to work, but the lower end of the Rising Fighter gearbox slider kept dragging on the floor. So, drill some new 3mm holes in the top end of the Rising Fighter part and cut the bottom off flush with the tub with a junior hacksaw.

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Whilst i was at it i dremmelled the steering aperture and fitted the long high torque servo saver to improve steering lock.

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Gave it a quick run and the rear is waaaay more stable. Put some slightly stiffer rear springs on now there isn't crazy anti squat. Getting there. 

On the shell i think i got enough layers of white on today that i should be able to sticker it up tomorrow. 

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Finally ran it off road! Grass was super grippy, and it was a lot of fun. Really happy with how its shaping up

Really narrow front doesn't seem to make it handle badly, but it does look odd. Really like the matching blue wishbones.

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