El Gecko

Super Stock TZ or BZ would be much faster and more powerful than the Sport Tuned you have, and round about a 17.5t brushless equivalent I reckon. According to a thread on here, even the newer silver can Sport Tuned is an upgrade over the black can.

I'm sure I've seen it around and used it as unconscious inspiration but no, this is my first time posting this mod. The pic above is of my Brat, which is the most recent one, still running original hex shafts. The bumpstops made the car incredibly smooth, even moreso than the Blaster with universals and my original Frog with no bumpstops and hex shafts. The Blaster is an ex-MudBlaster that is now closer to a stadium truck with a buggy body, or an "outlaw" buggy with stadium truck wheels. It was my first time trying the universal setup, and instantly had problems. So I went on a wild goose chase doing everything I could think of until installing bumpstops. The mod itself is quite simple if you have access to a drill, a file and a good pair of side cutters. I made the Brat bumpstops from aluminum sheet and only used a Dremel to knock down some of the larger areas to make it fit. Same with the steel ones I made for the Blaster. While a Dremel makes the process faster, it's not strictly necessary. And for that matter, I don't think it's even necessary that the bumpstops are made of metal. All you really need is a 90 degree bend and a hole for the mounting screw, and the rest can be filed down to fit. Thickness is around 1.5mm, and obviously you'd want to make sure it's even on both sides. But they are really trivial to make, as I've learned.

I don't remember which version of universals I have, but I thought "torque oscillations" were my problem, too. Until I added the bumpstops and it all went away. Now the car is smooth as can be at any speed. The typical 2.2 monster wheels are not well-balanced to begin with, and the large, soft MB tires make it worse at high speeds. I tried shortening the shocks too, but there is always a bit of slop there as it switches from compression to tension, so it was unreliable unless the shocks were limited more than I wanted them to be. The bumpstops are unaffected by slop or any other shock setup.

Salvaged from a childrens push toy...

Depends on your definition of "worse". I think they traded one problem for another. I too have never popped one of the original hex shafts, but they don't spin freely at full extension, bumping and clacking as they rotate. If you've got the car on the bench with wheels spinning, lift both rear trailing arms just slightly and you can hear everything clear out. The bumpstops help keep the driveshafts from attaining such a severe angle, which keeps the hex ends from binding and wearing out as fast, and can also help keep the original-style gear diff together for longer. Part of the problem with the diff is that the driveshafts tug on the ends of the diff yokes, forcing them downward toward the ground and causing a misalignment inside the gearbox. The bumpstops take the "pressure" off the diff yokes and help keep the diff together, straighter, and hopefully lasting longer. On the other side of things, the diff isn't as stressed with the dogbones and universals because they have less wiggle room before they pop out, but that means the bumpstops are basically required to actually drive it at more than half throttle (IMHO they're required for any ORV if you want to keep the diff/driveshafts of any type in working order). I would choose the universals because they're attached to the wheel axles, impossible to lose if they pop out unless the grub screw has also come loose. I have original hex shafts in 2 cars, and the one with universals and bumpstops did 12 stints of the last Racing by Post track without throwing any driveshafts. This is a car with sticky 2.2 road tires on Blackfoot wheels, so about the most flex one can get out of those rear trailing arms. Definitely "race-proven" in my eyes. I tried all kinds of other tricks and tweaks, but these bumpstops had the most immediate, significant effect on keeping the driveshafts in.

1. Try putting the rear arm stoppers on the opposite sides. IIRC, one side is smoother and allows more free movement of the trailing arm. Also, yes: the stoppers should be screwed right up tight to the chassis sides... no spacers otherwise the driveshafts are guaranteed to pop. 2. The 53908 universal shafts are great, but they need the rear suspension lowered at full extension otherwise they pop out every few seconds. The biggest issue on any ORV is when the trailing arm flexes while cornering. It's worse on one side as you discovered, but it's almost always the inside wheel that loses a driveshaft, because the inside wheel has the least weight on it, especially under braking, and the driveshaft end is the least engaged with the diff yoke at full suspension extension. Then you add the cornering forces flexing the inner trailing arm out from the chassis even further, and it's no surprise what happens. I made some little aluminum shims to solve this by slightly limiting the ride height, which to me is an acceptable tradeoff to keep those pesky driveshafts where they're supposed to be. My trailing arms and particularly the opening in the aluminum gearbox halves are all VERY worn out, and it hasn't thrown a driveshaft since. This fix works to smooth out the old style hex shafts as well, because even those bind and crunch and sometimes pop out at full extension. Tamiya should have included these in all ORV kits in some form once the problem presented itself, but I have a feeling they wanted to preserve as much suspension travel as possible.

It's always cool finding out about different forms of motorsport. Here in the States, "autocross" means something completely different, but the UK format seems like a lot of fun, too. Your autocross cars across the pond look very similar to our Pikes Peak racers, except without the giant wings. As for RC, I think you could definitely get close with a front hex conversion as @SlideWRX said. However, my thought is that the new TD-4 or TD-2 chassis with their cycle-style fenders would be a perfect base for a scratchbuilt body. Then you could use the Fuchs style wheels no problem, and the chassis itself would be a bit more accurate as well.

And you guys think hop-ups are a con?

Less caster meaning angle both knuckles forward just a few degrees. In the rere manual step 2, it says to align MP2 squarely with MP3, but if you rotate MP2 a few degrees off center, it will raise the rears of the steering arms, raising the ball ends in relation to the ground. Which puts them closer in line with the servo saver end, shortening the length of the required steering rods and enabling you to screw them into the plastic ends further. Being more closely aligned with the servo saver also has the benefit of removing a bit of bump steer, similar to the effect you would get from adding taller standoffs to raise the ball end locations.

I'm not claiming to be a Frog expert like the true expert you originally tagged, but just a suggestion--try running less caster on the front knuckles. That will put the ball ends closer in line with the servo saver by raising the rears of the steering arms, lessening bump steer and allowing you to thread more of the rods into the plastic ends. I'm still using original everything on my Brat, and even only half-threaded in, the linkages have been fine (same on my Grasshoppers/Hornets). Another fairly easy option is to get another set of Frog/Grasshopper/etc. steering rods and just cut/rebend the long one a bit longer than the short side, to give you more thread engagement in the ball ends. I can't remember how I got the balls out of my steering arms, but I think they're riveted in from the underside, so they'll just spin if you try to unscrew them. I drilled and tapped my arms for M3, and so far they haven't needed a locknut on the bottom. The steering linkages are actually not bad in stock form, but besides the "too short" problem, they're also let down by the notoriously sloppy front suspension arms. You'll typically have toe out when the front wheel camber is positive, and toe in under negative camber, just due to slop. The only way to really tune that out is to sleeve or otherwise strengthen all the pivots of the suspension arms (as @Frog Jumper mentioned, the brass sleeves from inside the gearbox work perfect for this, but I can't remember if they need to be cut down or not). Also I have never felt the need for a center servo fix. In practice, actually driving the cars around, it's really not that noticeable. The offset motor position has a bigger effect on the balance and traction than if the tie rods are equal length.

Did a few more stints today, made sure to follow the correct course line around the first few markers since I did it wrong last time No excuses other than bad driving, however still managed to improve slightly over all the previous tries, and now at least I have something recorded for the correct track. Don't think I'll have the chance for more attempts this week before the deadline, but this has been a fun one @Grastens!

We have a long history, doubt I could ever get rid of this one no matter what else happens.

I don't think thick grease like AW is necessary for the Frog diff. I just use a thin layer of standard STP bearing grease (lithium-based) like on all my other diff gears. The die cast metal gears are a fairly tight fit, which gives a bit of limited-slip effect just due to friction. Oddly, they don't seem to wear out very quickly, as I've got friction still in the original gears in my vintage Frog (yes, original gears with tons of "hard miles" still working perfectly with a 17t Trinity Sapphire motor and original hex shafts--and never a drop of AW). I've also been bashing the Blaster around all summer with its re-re diff gears, as well as taking it for a very spirited nine consecutive 5-minute stints of the latest round of Racing by Post, (don't worry, I had some breaks to let the motor cool down, change batteries, etc.) and I'm happy to report that the diff feels just as fresh and tight as it did when it was first rebuilt. And this is with a 21t brushed motor (16t pinion) on wide 2.2 stadium truck wheels with sticky tires on dry tarmac. Somehow, so far, it has survived. Although admittedly, the gearbox hasn't been cracked open in awhile, so who knows what kind of funky voodoo is going on inside!

The angle is probably a bit steep for a flat ramp (40% if we go "up 4 over 10"). I would only really go up to 15% or so unless you're driving a car/truck with significant suspension travel. Higher speeds needs a longer/flatter ramp, so it makes sense you have to slow down for yours currently. If you want the cars to go higher, but not as far, you'd have to build it like your bigger ramp, with a bit of curve/transition so the car gets a bit of kick at the top of the ramp. The increase in airtime may help you control the car in the air a bit. But if you prefer a flat ramp, we can take a cue from the ramps they use for 1:1 Stadium Super Trucks, which are right about 15%. I found the dimensions on the wiki page, and if we scale them down to 1:10 (rounding down to the nearest inch at 15% grade) we get a ramp that's 20" long and 3" tall. As you know, the actual ramp surface would be longer since it's the hypotenuse of that right triangle. I think that would give you a better "jump" given the limited suspension movement of a buggy. I have a feeling your car is bottoming out when it hits the ramp, and the chassis is getting bounced off its line from that impact. Or simply the abruptness of the transition onto the ramp is upsetting the suspension. What's the leading edge like where the ramp meets the ground? Your width sounds pretty good to me for a portable unit, but it's always nice to have wider ramps. (bigger targets for high speed projectiles vehicles)

I know it doesn't look like much, but it's really incredible how well this old thing drives!! It was essentially left for dead in a junkyard when I found it and have been slowly resurrecting it. We had a nice little bash session after postal racing on route 5 today

Finally had an opportunity to set up the course in a nearby parking lot, chance of rain today but none fell while I was driving, and the track* was a lot of fun! The Blaster was the only contender, although the Brat came along for moral support (and had a little bash session of its own afterwards). I've been making a lot of modifications to the Blaster recently, and to my surprise and relief, it actually worked perfectly for two whole battery packs of racing. The dogbones stayed in the whole time! And somehow the bald rear tires are still hanging on, too. *So, this time the driver excuses are because of poor track management. Had a few hiccups with the lap timer app, but the big problem is that I didn't double check the course map before laying the chalk. So instead of going around the outside of marker 2 and the inside of marker 3, I ended up doing a U turn around marker 1, between 1 and 2, then back out between 2-3 and around the outside of 3. It made for a very tight sequence of turns, and really slowed me down, but at least I've got something to record for this round. I'm hoping to get a chance at redemption later this month, but it's been fun so far! It's been awhile since I've done laps on a racetrack, and it was nice to be able to still get into a good flow fairly quickly, even if I was driving the wrong track

Totally right about the BF, but the RC10 (buggy) casts a long shadow! In the "Hobby Shop News" I have from winter 1990, there is an article comparing the first three racing trucks to hit the market, and Tamiya and Losi won that race with the King Cab and JRXT. The JRXT was directly based on the JRX2, with only a few parts differences. Traxxas wasn't far behind with the TRX-T, quickly renamed the TRX Eagle, then later on the Blue Eagle. The Hawk used a different molded tub chassis, and eventually everything got mixed together into the Rustler. The first Traxxas trucks used similar style 2.2 wheels as the BF, with bearings in the front and the same 5-stud hub adapter interface in the rear. The sidebar in the article says "Where's Associated's Truck?" and stated that there was only a single prototype in existence at the time the other three were already being reviewed.

I always forget that part. One tooth difference!

The Blackfoot gearing is exactly the same as the Frog "high torque" gearing except the motor spacer. The spurs and diff gears are all the same size, and both setups use 16t pinions. The Frog spur gear is obviously multiple pieces, whereas the Blackfoot uses a one piece gear, but they're the same ratio. The only real difference is the motor spacer on the Blackfoot so it can use the extra long 10t pinion gear for even further reduction. IMHO you'd just need to add a motor spacer and 10t pinion to your Frog with high torque gearing, and it might survive that field. But I suspect that nothing is going to run well there except a 1:8 scale 6S monster. Depending on the closeness of the mowing, the Frog might actually get stuck.

Agreed, I have one of those Radons too, and it seems a little lazy... not as much punch as I was expecting, although it does reach a decent RPM. I'll pull it apart at some point, I'm curious what's actually in there.

In case there was any doubt, this is why the new cheapo motors don't have as much torque as more expensive or older ones. Exhibit A: Snow Panther Hobby 17T TUNED MACHINE I finally got some time to pull one of these apart, and as you would expect, the cheapo 17T on the right has many fewer windings than the 27T '91 ROAR stocker in the middle, but you all were totally correct: the wires are either the same, or possibly even a smaller gauge! This means much less rotating mass and higher RPM, but also much less torque, which explains why they drive the way they do. I'm not sure of the turn count on the ancient modified arm on the left, but you can clearly see the thicker wires there. I'm curious to do some swapping around, to see how the old armatures respond to the new can. Assuming they work on similar principles as my HO slot car motors, they should perk right up since magnets are quite a bit stronger these days.

Perhaps my favorite track of all time! Technically I should be driving an R33 GTR this round, in NISMO 400R trim of course! I'd love to make an RC version of that one day. Bonus bonus points for running at night on wet tarmac?

Yes the chassis are nearly identical except a few details, but the truck body and those big wheels makes a big difference! Just explain it as "variations on a theme" so you get a different driving experience with each iteration. And don't forget to mention spare parts... there's a lot the same for both chassis, so spare parts for one are spare parts for the other. That's my justification for having a Frog, Brat, and what's left of a Mud Blaster (all the same chassis, all set up to drive completely differently). This also works for my Grasshopper, GH2, and 2 Hornets (although the GH2 is hers). Interchangeability aplenty!

I only have a rere GH2, but I think the chassis and gearbox are the same in all versions of GH2, maybe not exactly identical but the mounting holes will be in the same spots, things line up the same way, etc. The gearbox in my GH2 is identical to my 80s Grasshopper (1) except an extra piece of plastic on the front. As far as I know, that gearbox has been unchanged since the 80s except a few little things like that. The GH2 friction shocks will likely fit fine, but you'd be better off getting CVAs to replace your originals, or something aftermarket and oil-filled.

My thought was "well so can slot cars!" but of course, slot cars need special track, power supply etc. I can certainly see the appeal of Mini 4WD when other options are limited, they just never really took off here like it did in other places.