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Post by dave632 on Feb 17, 2019 10:52:14 GMT -7
Doing some testing with an unlimited T Jet I have. Running at 24v for some reason it is running slower than it had at 20v??? Anyway the body survived with no problems as the car hit between 39 and 42 MPH, running between .38-.42 ET. Will be fooling with this some more but there is no problem with stopping a car at this speed on my track. I did use an old Mustang body that the rear had broken off in the past.  Unlimited T Jet |
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Post by dave632 on Feb 17, 2019 13:38:08 GMT -7
Car is bending the 1/32" brass rod wheelie bar.
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Post by GTS on Feb 17, 2019 13:48:17 GMT -7
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Post by AJR on Feb 17, 2019 17:53:41 GMT -7
I can hardly wait to build one! I've got the fever. Crown gear is already my concern  . |
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Post by dave632 on Feb 17, 2019 18:03:23 GMT -7
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.
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Post by GTS on Feb 17, 2019 19:34:28 GMT -7
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? |
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Post by dave632 on Feb 17, 2019 20:16:38 GMT -7
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.
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Post by dave632 on Feb 17, 2019 20:19:41 GMT -7
I have another chassis I will be fooling with and I will install the aluminum top plate on it along with some brush tubes to see if there is any difference.
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Post by dave632 on Feb 17, 2019 20:20:48 GMT -7
Are we going to allow AFX 3 gear to run also???
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Post by dave632 on Feb 18, 2019 13:50:10 GMT -7
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.  brush tubes installed
 drill size .153 |
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Post by Deleted on Feb 18, 2019 15:10:18 GMT -7
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.
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Post by AJR on Feb 18, 2019 18:34:49 GMT -7
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.
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Post by dave632 on Feb 23, 2019 7:24:34 GMT -7
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. |
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Post by AJR on Feb 23, 2019 10:03:06 GMT -7
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?
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Post by GTS on Feb 23, 2019 11:26:17 GMT -7
You guys might already have this link but here is the link for those Delrin crown gears and the brass 9, 10, 12 & 14 tooth pinions. I stumbled across it looking for other items. I've never ordered from this vendor.
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