Pinion screw hitting spur

[MetalNut]

Quick question. I'm getting close to finishing my kit and just tried to install my HH Crawlmaster. I'm running parts of the "bulletproof" transmission, namely the SuperShafty top shaft, Robinson 32p 56T slipper spur gear, and a Robinson 32p 12T pinion. There isn't enough shaft on the Crawlmaster to move the pinion set screw below the spur gear, so it hits on every rotation. Is this a known issue with this setup? I haven't read anything about it.

I know I can shimmy the motor, but I'm worried that'll make it a bit wobbly/unstable with just two attachment points. Ideas? Am I just missing something obvious?

Thanks!

[RusT808]

Will flipping the pinion around help?

[MetalNut]

Originally Posted by RusT808

Will flipping the pinion around help?

Unfortunately no, that makes it even worse. I ended up putting a small washer between the motor and the motor plate on each of the two screws, then moved the pinion as far down on the shaft as seems safe, and now it's ok. I'm just not feeling great about the little washers keeping the motor stable under torque.

[RusT808]

Maybe a larger pinion and spur combo.

[RusT808]

Or carefully grind the flat spot a little more with a dremel using the sandpaper drum. I did on my HH puller, had the same issue you have here.

[Postclanker]

So...your pinion set screw should not be sticking up at all. Are you sure you are screwing the set screw down on the flat side of the motor shaft??? It should seat flush when tightened down. A 14t pinion would be a 4:1 ratio and help this issue and your gear ratio.

A picture or two might help us help you.

As far as a washer/shim goes, try using a slightly longer screw and a small lock washer. I've been using this on motors for years and no issues.

[RusT808]

A 9t or 10t pinion will not have the tooth clearance for the set screw. I'm guessing this is what he is using.

[Postclanker]

Thought he mentioned a 12t...
Still would like to see a picture. I don't think I've ever run anything smaller than a 14t. The grub shouldn't be sticking out at all.

[MetalNut]

I'm setting it up with a 12T pinion per Harley's motor thread. To quote "Short Story, 56/12 32p (brushed)".

That is a slightly smaller ratio than the stock, which I believe he mentions to be 56/14. I figured if he's recommending the 12T it'd be an easy fit.

I triple-checked that I'm tightening the pinion set screw on the flat spot of the motor shaft. I guess I'm going to go check one more time

[MetalNut]

Ok, I took a picture for you guys. It definitely doesn't look right, but the set screw IS lined up with the flat spot on the shaft, as you can see. Maybe I have a bum set screw?

[Postclanker]

Is that grease on there? I've never seen that done

Have you tried another grub screw ?? Everything else looks in order...with the exception of the grease of course....

[MetalNut]

Originally Posted by Postclanker

Is that grease on there? I've never seen that done

Have you tried another grub screw ?? Everything else looks in order...with the exception of the grease of course....

Yeah, I'm kinda old school and like to run a little grease on all metal parts. I took that picture before I wiped off the excess, it's actually cleaner now

I don't think I have another set screw of that pitch, unfortunately. I may have to figure out what size I need for that RR pinion and try to order one. Or I may just shimmy the motor a little more, as the screw is still hitting a tiny bit.

This project will never end

[Postclanker]

Ya, wipe it clean ...is your spur a metal one...I've been looking for 32p metal spurs...if so, where'd you get it?
Most pinions will come with their own set screw...the one you have in there looks large/long. If you have another one try swapping them

[MetalNut]

Yes, spur and pinion are both metal, Robinson Racing. They are what Harley suggested in his "Bulletproof Wraith" thread. Keep in mind the spur is actually this one, and will not fit the stock wraith shaft. You have to get the bigger shaft from SuperShafty.

I'm using the set screw that came with the RR pinion, it's a 5-40 1/8" screw. It's definitely too long for this application, but it's what they gave me. I'm going to see if I can get a 5-40 in 3/32".

[Postclanker]

I would try to shim that nice Robinson spur out a bit if you can. Although after some thought, not sure how you would do that. Your better bet might be to try another pinion gear.

Sorry, not much help...good luck bud

[ninja turtle]

File the backside of the pinion down a little.

[Postclanker]

Originally Posted by ninja turtle

File the backside of the pinion down a little.

Great idea...put it to a grinder if you have one...

[crawlhog]

Originally Posted by Postclanker

Great idea...put it to a grinder if you have one...

just grind it down , not rocket science.

insert spoon , start feeding

[MetalNut]

I've ground enough screws in my time to know that it's very easy to mess up the threads. The way I usually do it is to put a nut over the screw first, grind off the tip as much as I need, then screw the nut off, thus "cleaning" the threads as it goes.

If I'm going to do that with the pinion set screw, I'd have to do it while it's in the pinion, for the same reasons. For now I just shimmied the motor with a washer, that seems to be working well. If it fails, I'll grind the screw

[ninja turtle]

Use a file on the screws and you won't have that issue with the threads.

When I said to file the backside of the pinion, I'm talking about the part of the pinion that is hiting the motor. Also I would use a file not a grinder as the pinion is tiny and not very easy to hold on to. You could use needle nose or something like that but you could mess up the teeth on the pinion.