RC10Talk - The Net's Largest Vintage R/C Community

I got my worlds today so I figured it would be a good time to figure out wtf Associated did. I have three scenarios all played out

-stock worlds case and idler
-6565 case with worlds idler and extra bearings
-6565 case and 6570 idler (aka "how it should be")

I have a couple pics of the parts I had at my disposal, all new and sealed. My top shaft is the same as the one in the bag so I suspect the machining is correct. I haven't bolted the slipper on yet. Also, I had my original topshaft ready but didn't need it

I know running that idler in the old case with double bearings isn't proper, but it does help show the idler is crap as well as the case. Quit redesigning the wheel, the old ways were MUCH better.

Video:
[youtube]3W1f9dyMFqI[/youtube]

Well on the bright side, we have NEW outdrives at sticker price that work with our old cases

And you can still get the 6565 cases and 6570 idlers too. For now anyway!
It feels like a real stealth now

In my new US case I found a fair amount of side to side play with the diff compared to the worlds case. None of the tolerences seem as tight as the original parts, except the gear mesh which is even worse in my opinion.

Not having messed with any of the rere parts, are you saying that all of the binding issues are because the new idler gear is crap? Using the old idler gear in the new case solves it?

That combo can't be tried because there is no room for bearings. My test shows it still binding after the case swap while using the new idler, so it at least contributes to the problem.

the idler gear sounds like it's most of the issue. from hard to spin to rough in spots, that all points to an out of round, and at the high side of spec molded gear.

if you can stick a b2/b3 idler in the kit case, I wonder what would happen.

out of curiosity, how hard was it to get the bearings in the idler? if the bore is undersize, that will make the gear expand when installing.

jwscab wrote:if you can stick a b2/b3 idler in the kit case, I wonder what would happen.

the b2/b3/t3 idler is larger. i actually didn't know that until this new stealth came out. i had always assumed it was just the larger diff gear by itself that gave that trans it's 2.40 ratio.

scr8p wrote: i had always assumed it was just the larger diff gear by itself that gave that trans it's 2.40 ratio.

I might be reading it wrong, but the idler diameter doesn't effect the ratio at all- it's just an idler. That said, it looks like the 6570 and 6569 are 26 tooth. The bearings were not a tight fit. I do not doubt that a break in would help, but our originals never needed it and neither does the USA case and idler

i'm not good with figuring out how they come up with internal final drives.

but to me, i would think if you take out a 26 tooth idler and install a 28 tooth idler, it will slow the speed of the diff gear. does that not change the final drive of the trans?

no...idler does not change gear ratio. you could have 15 gears all in a row of varying tooth count, the only ones that matter are the first and last to make up the ratio. now, the speed at which those idlers spin will all vary, but they don't 'drive' anything.

hmm...i thought all the idlers were the same tooth count? just changes in the bearing/axle arrangement?

if they are indeed different that is starting to make sense. they figured out how to make the one that fits b2/b3/t3/t4, and this one with a different tooth count was not made properly, and it's just for this case only.

jwscab wrote:no...idler does not change gear ratio. you could have 15 gears all in a row of varying tooth count, the only ones that matter are the first and last to make up the ratio. now, the speed at which those idlers spin will all vary, but they don't 'drive' anything.

well, i'll go with you guys on that. it just doesn't seem right to me. i'll have that "light bulb" moment eventually.

jwscab wrote:hmm...i thought all the idlers were the same tooth count? just changes in the bearing/axle arrangement.

i thought so too. until i tried to put the idler from my 2.40 trans into the worlds stealth case.

yeah it's kind of tricky to think about. think of the tooth engagement, an idler will move one for one with the drive gear and driven gear, but the drive gear may have 4 teeth for one rotation, while the driven gear might have 40 teeth, so therefore a 10:1 ratio to get a full rotation. idler is just along for the ride and to route the power through the teeth.

The only time an idler matters is when it is a cluster gear.

Anyway, back to the idler- I could swear I read earlier that they used a t3 idler but obviously there is a new parts number per the manual- not sure what their thinking way. I think the idler is more of a problem than the case to be honest. That's assuming no topshaft issues too- mine is a properly machined one. Lots of places for issue when the quality control is nonexistant

scr8p wrote: well, i'll go with you guys on that. it just doesn't seem right to me. i'll have that "light bulb" moment eventually.

Just consider the math. To get the final ratio of the 3 gears in sequence you can figure out the ratio of the idler and top gear and the idler and diff gear then multiply those two values together:

28/20 = 1.4
48/28 = 1.714285714
1.4 x 1.714285714 = 2.4


or, because you're just multiplying two quotients, you can simplify the math by just dividing the tooth count of the diff gear by the tooth count of the top shaft:

48/20 = 2.4