A tale of 2 stealths

[rccars4sal]

Allright, what we have here is ahhh,, strange, and yes, strange. Why 2 stealths?

First pic, top to bottom, old grungy stealth, new USA stealth, and new worlds kit stealth cases.



Second pic USA gears on left, black diff. Worlds kit gears on right, hollow idler, yellow diff.



Third pic the side by side build as it will happen.



4th pic worlds kit top shaft at 1.057" from tip to back of the flat.


5th pic USA stealth top shaft at 1.098" from tip to bottom of the flat. These measurements will be re done, because a difference in thread length might not matter. Its the length and position of the flat that seems to matter?



Click the pics for a couple more shots of my as always cluttered work station.

More to come.

[jwscab]

measure from the face of the gear to the edge of the machined flat. that is the critical dimension. where the bearing sits on the shaft on the motor plate side. That will tell you immediately any differences.

also, before assembly, please put the motor plate spacers in the new stealth and compare the height with the worlds case, there could also be some differences in motor plate location. If your dial calipers have a 'tail' on the movable jaw, you can use it as a height gauge.

[GodSpeed]

Awesome post. Thanks. Will stay tuned.....

[marlo]

Great info, I've been wondering about the new stealth's for a while now.

[rccars4sal]

Got them done. Diffs: The USA diff is familiar, the balls click in like they should. After its built, it didnt tighten down as much as I expected. Screw bottomed out, then back 1/8 turn, and it just never dit tighten up then release. It feels good, but wondering if it will loosen noticeably after running. The worlds kit diff slightly diff erent. The balls fall in loosely, no little click. After its built, it did tighten up nicely, then felt perfect when the screw was backed out 1/8 turn.

So, on to the assembly. Both units have a little roughness and will need broke in. Neither too bad in that department.
The worlds car trans went together requiring no re work. No rubbing of the slipper plate.

1st pic the worlds kit top shaft. .518 from the flange of the gear to the edge of the flat.



2nd pic the USA stealth top gear. .492 from the flange of the gear to the edge of the flat. A difference of 26 thousanths, or about 5 sheets of paper,, or a freakin MILE in machinist terms. This is a huge in consistency in the production process,, or possibly a whole different standard dimention???



I had measured the spacers at .345" after removing the molding flash. I had to file them down to .32" to make the slipper plate not rub. So, I took .025 off, almost the same as the difference in the shafts. Makes sense. I also had to file the bolts down so they wouldnt rub the slipper plate.

Last pic the two trans tip to tip of the slipper shafts. You can see on the right side there is about 1 extra thread sticking out from the nut. It had to be tightened down that much more( roughly 25 thousanths again) to get the same "feel" as the worlds kit slipper. Worlds kit on left, USA kit on right.



Another thing noted. The USA top shaft was about .0003 smaller in diameter than the worlds kit top shaft. What this means is it wobbles slightly more in the bearings. Probably a tolerance of +- .0005 on the shaft diameter is acceptable.

I think They are both good. The USA trans required the rework of the spacers, and the shaft is machined a bit off I think. Who knows what their manufacturing tolerances are though. They might be in spec.

[scr8p]

seems to me that all you really need, if you have a problem top shaft, is tap the gear away from the milled flat spots. that will throw everything away from the motor plate.

[rccars4sal]

I didnt know the gear was movable on the top shaft. That would take .026 length of shaft out from being supported by the bearing. Not much I know.

[jwscab]

The shafts could be OK but the gears pressed on wrong or not to spec.

[RichieRich]

So the gear is not being placed on the shaft at the right point which is either creating a tight case and/or making the slipper touch the motor plate?

[Charlie don't surf]

Tale- not tail as in appendage-

[askbob]

Tail- as in been out chasin' tail?

[rccars4sal]

I really dont think the gears are placed wrong. Upon visual inspection it was pretty obvious that the machined flat went farther back. It would have been more obvious if the gear was closer to one end compared to the other. I will check today though. Thought that looked kinda funny,, but couldnt quite place it. tail tale.

By the way,,, Ive been playing with both transmissions here and there,, spinning the big gear just for fun ... The play in the USA top shaft is pretty bad. I can make the gears "knock" together by spinning it quick with my fingers. The worlds gearbox seems (.)(.) in every aspect. Ima see if TA will replace the top shaft. I dont like it at all.


O/K,, more numbers. Length of the machined flat USA part. .442" . Length of flat worlds kit top shaft. .398" . Diff erence of 44 thousanths, or approximately 2 miles.

Distance from end of shaft to flange of gear on the back side .142 on the worlds kit part. .137 on the USA part. Difference of 5 thousanths,, totally acceptable in my book considering its a manual job pressing parts together with a broach. Generally the way that works is there will be a precision stopper in place and when the worker goes to press the 2 parts together he just forces the broach down until it stops at the precision stopper. So, a variation of a few thou is pretty good.

Now,, consider Im using dial calipers accurate to .001 and I can pretty much split the distance between the lines to estimate around .0003. My measurements were made very carefully, and repeated to make sure the numbers are consistent. The pics with the calipers oriented to the parts may be slightly off, because of laying them down and getting the pic. Anyway,,,, I hope this sheds some light on possible reasons for new stealth problems. I expected the worlds kit to be the problem child after reading the threads concerning slipper clearance. In my case it was the kit no 6560 steath trans kit that has problems. Im confident to say its a top shaft that is machined pretty far off nominal dimensions for both diameter, and length of the flat section that is the issue. Probably, the shaft is usable as is, but pretty sure this gear box would chew the idler up pretty quick with a brushless and lipo set up. Also, there might be issues where the motor plate attaches to the back of the chassis because its now .025 out of position sideways. Havent built the rest of the car, so not sure if there is that much room for error between the gear box mounting bolts and the motor plate rear mount holes to make it work without hogging out the 2 rear holes in the chassis. Ehh the 6560 trans is going on a custom build,, so no worries about the new mint machined worlds chassis needing cut into!

[harvey]

My observation after beginning assembly of the trans included with the worlds kid is that the problem with roughness lies with the case itself. The gears are too close together. It has been mentioned that there is a tight spot in the rotation, and I found this as well. However, the tight spot is not consistent. Meaning, it does not occur every revolution. If only the top shaft were out of round, the tight spot would be once every revolution. Ditto if it was only the idler. Because the tight spot is not every rev, but seems random, it indicates that neither gear is perfect, and binding occurs as the ratio between the two gears brings the high point on each gear together.

I experienced the tight spot with the top shaft from my B4, but to a lesser degree. However, it works perfectly in the b4 trans. This leads me to believe that none of the gears are perfect, and that this is normal. It only becomes a problem when the gears are too close together. My theory is that the peaks of the one gear teeth are bottoming in the valleys of the other, hence the binding. (just like a tight pinion/spur) To remedy this, one would have to reduce the diameter of both of the gears. So one could spin the top shaft in a chuck and sand the top off the gear, but this would change the profile of the teeth, and the way they ramp off of each other. I don't know how one could to spin the Idler. Also, that would change the gear mesh with the diff gear.

I know some folks have been sent replacement top shafts and I would like to hear what improvement is noticed specifically as to gear mesh, but it seems to me that a more effective solution would be a replacement trans case with the one that has been called a USA case, along with the older style idler. The slipper problem with the deep top shaft flats does not concern me as much as the gear mesh, since it can be remedied with the previously mentioned spacer from the b4 trans.

Please feel free to debate, as my ego is not fragile and I just want a smooth tranny!

[GoMachV]

I have in the past spent a lot of time finding burrs on gears, and true- one rev of the topshaft should provide a noticeable and repeatable "bad" area if it were the problem. If the concern is every rev and a half, it could be the idler. If it's every couple revs then the lower. Those are estimations but you get the idea. I would also like to hear from someone with a rough trans that has removed the diff or topshaft to see which is causing the concern.

The case may be holding the gears too tight but the shafts are being held at a constant, only the rotating parts can cause the feeling to come and go

[foots]

Too much saki on break.