Need some tech advice re: Turbo Optima gear upgrading

[Coelacanth]

Never heard that before, ED...thanks for clarifying.

Here is the OT-74 limiter gear assembly that I just received. Hopefully it's the better of the two versions...anyone can confirm?

[Mr. ED]

Never seen that before. If it works well, I'd love one for each of my ultimas.

[Coelacanth]

Never seen that before. If it works well, I'd love one for each of my ultimas.

The guy I bought it from sells it for cheaper than most of the others I saw, and has 9 more.

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=290423344267&ssPageName=STRK:MEWNX:IT

[ROH73]

That's the one that comes with the Turbo Optima; I've never had any issues with it.

[Coelacanth]

I checked my manuals for both the Turbo Optima and Salute, they both show this particular limiter gear. Anyone have experience with the previously pictured unit, the one with the curved spring washers?

[losiXXXman]

Let me see if I've got this straight. Does the OT74 act somewhat like a slipper clutch, or is it just protecting the internals from drivetrain shock of landing with the throttle pegged? From the pictures, the shaft of the unit is notched, so you'd have to use the set scew style final pinion right? anyone think the shaft could be crossdrilled to allow the use of the plastic pinion?

Since I found a thread about these gearboxes, I had a few other thoughts... Has anyone trie making their on 48p internal conversion using a traxxas diff maybe? I was also thinking about trying to use the frog spur cluster gear on the external side, the small one is 18t which appears to match the Ultima stock spur cluster. You could then have spurs of 49, 50, and 52 teeth.

Thoughts??

[Coelacanth]

Let me see if I've got this straight. Does the OT74 act somewhat like a slipper clutch, or is it just protecting the internals from drivetrain shock of landing with the throttle pegged? From the pictures, the shaft of the unit is notched, so you'd have to use the set scew style final pinion right? anyone think the shaft could be crossdrilled to allow the use of the plastic pinion?

My understanding of that part is that it's a torque limiter. It's referred to as such in the Turbo Optima manual, and the part doesn't exist in the original Optima; it's just a shaft with O-rings and washers.

It's interesting what you said about basically reverting to an Ultima final pinion (plastic)...I recall someone suggesting that to me--I think it might've been fireboy on eBay, whom I've bought Optima parts from including an OT-76 hard final pinion. It was suggested to do that but I never got any confirmation from anyone who actually DID that mod, if it was successful or not. Just rumors, I guess. It would involve replacing the shaft (or cross-drilling it for a pin, as you stated) and final pinion gear. I think the part number is UM-5 gear shaft set, or maybe UM-1 gear set.

I'd be interested to know exactly what would be required to go that route, as supposedly the plastic gear would last forever (heh!)--at least compared to the stock soft aluminum final pinion, which is probably the biggest weak link in the Optima drivetrain.

[losiXXXman]

Well, I had an Optima Pro way back, but couldn't tell you anything about what was on that. I picked up an Outrage from ebay, that I am turning into an Ultima Pro-ish buggy. My gearbox has the plastic pinion with a roll pin slot, and the shaft is cross drilled. So, picking up an outrage should get you where you need to be. I got mine for $16 shipped!!

I've never understood how a plastic part could be more durable than aluminum, I guess aluminum is soft hence the need for the hardened one for durability.

[sgirouard]

Sorry to bring back an old thread but I'm hoping someone can help me.

I picked up a Turbo Optima with the following OT-74 limiter gear

I have the gear, but I'm missing the parts to mount the gear. Does anyone have a picture of this gear "undone" or instructions, so I can see what I'm missing. I'm assuming it's a washer and screw, and does anyone know the size of the screw needed?
Here is mine

[Coelacanth]

Scott, in your picture, it looks like someone has installed a clutch bell or something where the limiter gear needs to go. Ordinarily, this is just an open hole in the gearbox side-plate and the limiter gear shaft goes inside there, and then through the final pinion gear inside the gearbox.

See if you can remove whatever's going on in the area shown in the red circle. You may have to first loosen the grub screw in the final pinion gear by opening that top "D" hatch in the gearbox to let that mystery assembly pull out.

As far as the limiter gear goes, the shaft end where the gear goes would probably be threaded, and the washers, bearings, gear, and wishy-washers would all go onto the threaded part, and attached with a reverse-threaded nylon lock nut.

[sgirouard]

I ended up buying the one with the spring that you pointed me to Marc so I'm going to install that, BUT...

I did take this one apart and it appears to be stock. The counter gear fits over the part you've circled. I'll take pics the next time I get a chance to work on it and show you. I dont think there's any after market or "funky" home made things going on here.

It looks like I would need 3 washers and a screw and I'd be able to assemble it. But I can't find any diagram of this spring washer version of the limiter gear.

[treehugger]

.

[sgirouard]

Is that the diagram of 3 washers and a screw Treehugger?