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Ha ha , way back in the day my friend had a Kyosho Progress 4wds , he learned to hate it ! There was too much slop in the steering linkages and you just could not get it to run in a straight line for love nor money , great round corners though , and the chain tension was a nightmare as well .
There's just no way to keep it looking like a Scorpion and have rear wheel steering , I'd have to loose those beautiful alloy trailing arms !

mugenbulldog wrote: ↑Wed Apr 12, 2017 12:47 am Two words: 4 wheel steering. Problem solved!

Widening the front track will also improve steering. I believe Dadio mentioned his goal of narrowing it, hence the problem surfaces. Lengthening the wheelbase reduces steering. Narrowing front track reduces steering. Not enough weight or downforce up front reduces steering. And obviously, servo throw will affect how much the wheels physically turn left/right. Other things will affect steering, but less significantly.

I was actually trying to reduce servo throw with my Barney build because the servo saver wanted to move beyond where it was capable, and binding on a part of the frame. I just had to adjust the endpoints with my transmitter and that corrected it. The Optima was known for having understeer issues, but my build customizations widened the front track significantly, and there's also probably some added weight up front...Barney turns quite well now, good turning on acceleration compared to my original Optima.

My desire to reduce the front track was to rectify it being wider than the rear after fitting the Optima front steering hubs , it was only to return it to stock track or parallel to the rear , it was never intended to reduce the track from stock so it should not be affecting steering , the issue is more in the design of the steering system i installed not having sufficient traverse in the wrack , this i can rectify by moving the ball joints inward on the steering hubs giving more steering angle for given wrack travel ,pretty easy to just drill and tap new holes in the hub arms , this will probably give greater angle than is needed but i can reduce end points to fine tune it .
With the front gearbox and drive train it should have far more weight over the front wheels than stock so that should not be an issue in terms of steering .
There's now way that I'm fitting a front wing for additional down force , it would be totally out of place on this build , I'd rather return to 2wd .

I wasn't making suggestions, just outlining the items that significantly affect turning ability. Those items are each a sliding scale where there's a particular point that's optimal, for a given car and driver.

If the wheels don't physically turn enough, I agree that adding holes to reposition the outer tie-rod ends more inbound on the knuckles would get you there, and might also address the bump steer issues you mentioned. Maybe even trying a different servo could help, as different servos have different throw ranges.

I was frustrated by, and had to solve, all these issues with some of my builds...mostly the Barney car and my buddy's AYK Buffalo, it has a front end design quite similar to the Scorpion. Just trying to help.

I can take all the help i can get believe me , i just drilled and tapped the new ball joint positions on the hubs and moved the ball joint in on the servo horn , doing the two re positions it has greatly increased steering angle and meant i could increase the servo travel , in the previous geometry i was at 61% end point limit and now it's up to 81% , this should improve not only the turning circle but also give greater control as I'm using more servo travel .
One bad thing , our young border collie found and chewed up one of the brand new front tyres , never even glued to the wheel

After adjusting the steering linkages i got a chance for a road test this evening , on the road it's a little low on straight line stability but i think that's largley down to tyre choice , there's no understeer anymore , in the short grass of my front garden it was really transformed , tracked nice and straight and turned nicely .
The only thing that surprised me was that it still pops wheelies even with the extra weight on the front axle .
I still have to make a chain tensioner as there's a little slack that makes it a little noisy but other than and a little finishing off of some parts and some paint then she's finished .

I'm an idiot , after the dog chewed up one of the front tyres i re fitted the wrong size front tyres for the road test , much smaller than the rear ones , no wonder it had little straight line stability on road ! Off road was much better because of the lower traction .

Well several tests later and i have nice steering ,chain drive working well , there's only one problem it keeps spitting out front drive shafts ! I'm going to try a cvd shaft , it's not in keeping with the build but it will have little visible impact , i could extend some of the upgrade UJ shafts but they are way too expensive , usually £35 plus P+P if you can find them .

The cvd shafts arrived today and they fit the steering hub well but are slightly too long and the pin in the dog bone end is too wide , i have a set of Scorpion dog bones coming so it's a simple matter of cutting and joining the two shafts at the right length .
After that then all that's left is a chain tensioner and paint yay !

we;ve gone too long without pics - give us some eye candy!

He he , theres not much new to see other than the front wheels/tyres and a pair of overlong cvd shafts sticking out the bottom of the car , I was away on my holl's for a week and we had stock take at work in the evening's this week ,this weekend it's re carpeting the living room and preparing for a Ww2 renactment next weekend so little time to do anything , not that there's much to do till the new front shafts arrive .

The scorpion dog bones arrived today and I found a little time to make sleeves and cut and silver solder the two parts together but by the time I was finished it was 10.15pm , where does the time go ! So it's road test in the morning yay !!!

Well the test drive went perfectly , it even withstood a cartwheeling crash ! I'm not even sure i need a chain tensioner yet ,probably will as the chain stretches but not yet .
only downer is with Photobucket being too glitchy to work right now so i still can't give any photo updates , i'll try later , i'll see if i can persuade someone to help video it in action as well .

photo update showing cvd shafts and wheels , im more happy with the silver soldering on the shafts and i made the sleeves slimmer as well so they look neater at least to me .

That's awesome! You need to festoon it with a few more stickies now to liven up the body a bit. And we all want a video of this masterpiece in action!!!