You have to use silifoam tires, they are the only ones I have been able to keep on high MPH cars. I used some old ones on the Mustang and it shredded them, pulled the coating off but they were pretty bad when I put them on.
You have to shim the crown gear to tight tolerances for it to survive. I try for about .001-.002 and you need a straight crown, Delrin helps. A lot of slop between crown and pinion and you will be replacing crowns every few runs. Wizzard sells .003 .005 & .010 shims with an .065 center hole.
Built another chassis with brush tubes and stock crown with tight clearance and it ate the crown in about 3'. The other car I have like this has a brass crown. Most of the time the stock crown will last longer than this. Used a .153, 5/32" drill for the brush tubes then soldered the tube to the bottom. Be careful soldering the two together, pre tin all of it, or you will melt the chassis. Can anyone make 15-18 tooth brass gears for these cars there is surely a need for them. I think Eagle used to make them but he does not anymore.
yep, the weakest link in the drive train will fail everytime. Eric Hirt from the York area of south central PA had cut some brass 15 tooth gears for the outlaw t-jets we were running. he is no longer associated with slots and Sgrig bought up and used all the remaining stock years ago. the kind of torque that is being developed with low ohm armatures and high magnetic field magnets is difficult for a 50+ year old toy to handle. the simple answer is to back off the power a bit. the CNC cut plastic crown gears aren't going to hold up much better because they are developed for long term high RPM use, not instant torque.
so, unless someone sets up to manufacture brass crown gears, we are limited by the amount of stress plastic gears can manage. and, understand, the gear train is under even more stress shutting down once the armature is no longer powered.
Yes Sir that is all true. Sjracer told me about those gears one time. That was all well before I got started back in the hobby. Since there are no alloy gears available, downforce vs wheelspin will be the key to survival. I have a couple of ideas that might help me out?? I learned a LOT during the 4 gear unlimited build phase we went through here. The 4 gear is a much weaker platform for this type of build in my opinion. So it will be interesting how things go. I am up for the challenge.
I can hardly wait to build one! I've got the fever. Crown gear is already my concern .
I'm curious how the OS3 delrin 15 tooth crown gear holds up to these demands. They suggest using their pinion gears which come 9, 10, 12 or 14 tooth. Would these still be concerning?
I have not tried a Delrin gear but I don't think any plastic gear will hold up for long. I have a couple of AFX chassis with hot arms in them and they seem to last a while. The T jets with the brass pinion seems to kill the plastic gears quickly.
Last Edit: Feb 23, 2019 11:47:58 GMT -7 by dave632
I have a couple of 20t predator gears that I have used successfully in my PSO builds. The mesh is much better than the stock gear so I think it will work...better. Any plastic will be short lived though. I had a few of Eagle's preliminary brass castings, but they were just unuseable...bummer. If a car can be built that can survive testing and race rounds in it before failure, that's all we need. Sounds good anyway.....lol. I'm also thinking that maybe something larger than the tiny 9t (I think) lower cluster gear would be easier on the crown (fewer rpm's. Maybe 12t?? I know that's not a cure all. Any thoughts on that?
Last Edit: Feb 23, 2019 10:05:45 GMT -7 by jjwallace