If I have the robinson racing is the process the same to lock the tranny in second gear?

Hmm, I guess I missed some of these questions. If it's not too late:

@jnev: I had some Ti coated bits I used. Even so, I wore a bit out doing this. So, get a couple and use cutting oil to help wear and cooling.

@David: The Revo outdrive is substantially larger than stock or even the Jato outdrive pins. If you use the Revo pin, the hole in the shaft will be too big and there won't be much metal left in the shaft and the shaft might break instead. The Jato pins are slightly larger and seem to be made of a different type of metal and have held up where the stockers didn't.

jacobsjo87: You mean the RR internal metal gears? If so, the process is about the same, you might have to drill the necessary holes. Even if the holes are present, you'll have to tap some 4mm holes as well. The stock 2nd plastic/nylon gear has holes arrayed evenly across it so it's easy to self-tap some 4mm screws into it.

Which CB and 2nd gears are you guys using to start off with ?? And can you give me a link to the r/c monster revo motor mount ? Thanks for any help

Most, if not all, aren't using clutchbells - we're using Mod1 pinions (scroll down) . Second gear depends on the user. Standard ratio works fine, but I use the wide ratio set for a taller transmission gearing. This allows a better range for spur/pinions.

This is the motor mount: http://www.rc-monster.com/proddetail...d=RCMrevomount

Nitro Revo Transmission Pin Mod
 

A buddy and I were at the track today playing with the Revo and Jato and I blew my spare Revo tranny. This was the one I had not done the "pin mod" on, so I thought I'd snap a few pics as a sort-of "how to"...

The broken pin:

http://scriptasylum.com/forumpics/pinmod4.jpg

The Revo FOC tranny screw pin is a different color than the stock chrome-like tranny screw pin. I wonder if they are hardened and stronger? Well, I called Traxxas and they said "they might be". Huh? Oh well, no real help there. They did say I should loosen the slipper to help control the torque, but then I'd lose much of the BL snap. Might as well drive a nitro! :smile:

Assortment of pins to choose from:

http://scriptasylum.com/forumpics/pinmod3.jpg

The Jato pin is too short to use anywhere in the tranny, but is included in the pic just for reference.

I noticed that whenever a pin broke, it was right where the threads meet the shaft, so that must mean that that spot is the most stressed. So, I modified two of the stock pins so they are about 7mm long each and then threaded both screws on each side of the gear hubs so the shaft tips meet inside the shaft. Below is a pic of the modified screw pin:

http://scriptasylum.com/forumpics/pinmod5.jpg

When cutting the black FOC pins and the original chrome pins (same size, diff color), the black ones seemed to take longer to cut with the dremel, so I think they are harder. This method has an added benefit: Since both sides are now captured, if a pin does break, the broken end won't fall out and mess up the other gears.

Picture showing the relative shaft diameters and gear hub thicknesses:

http://scriptasylum.com/forumpics/pinmod1.jpg

As you can see, each of the three shafts are different in diameter, so there is easy no "one fix for all" solution. The output shaft seems to be made of a softer metal so it is pretty easy to enlarge the hole. The input and idler shafts seem to be hardened so it is a PITA to drill. And the smaller shafts aren't big enough in diameter to hold up when drilled out.

Steps for each shaft:


Input (top) shaft: Since 2 modified pins will be used: in the plastic gear hub, enlarge the hole on the other side of the gear hub (opposite the threaded side) using a 7/64" drill bit to allow for the threads of the second pin. Modify two of the stock chrome pins like in the picture above and screw them in. The chrome ones are OK to use here because the pins have less force being exerted on them due to the gearing.


Idler/middle shaft: Basically do the same thing as the previous step, but use two of the black FOC pins instead. The pins here need the extra strength.


Output shaft: Since the output shaft is a softer metal, and has enough diameter, drill out a 2.5mm hole in the output shaft and the gear hub. There is no suitable "standard" size that properly equates to 2.5mm. Then drill a 1/8" (or 3mm) hole in one half of the hub to allow for the larger pin threads.


Another alternative I haven't tried is to use either a cut allen wrench or drill bit shaft instead of the 2mm pins for the input or idler shafts. A 2mm wrench may be strong enough without needing to enlarge the shaft holes. You'd just need to file off the "points" of the allen wrench so it will fit. If done right, you could just use a bit of muscle to press-fit the pin in place. If it's too loose, you could epoxy or JBWeld the ends of the pin to keep them from falling out.

I torture tested this setup and it seems to be holding up very well.

So after this mod is done, what would be the spur/pinion combo that would make it equivalent to 72/12 on an E-Maxx transmission. That is assuming that the Revo trans is equipped with a close ratio.

Reason I'm asking is because I might end up using a Revo trans instead of an E-Maxx trans for my E-Revo project, and I'll be running the Novak HV6.5 setup.

Welcome to the forums!

Using the close ratio tranny, a 40T spur, a 10T pinion will give you the same speed given the same motor, voltage, etc.

For speeds in the 35mph range, I would go with the wide ratio tranny option, a 40T spur, and a 14T pinion. That seems to work best for me, and the wide ratio seems to let you use a more common set of gears while still offering some adjustment options.

BTW: I used this calculator to get this data...

Thanks for the welcome, Brian.

Great info you just gave me. I think I'll choose the wide ratio route that you just suggested.

And thanks for the link to that calculator.

Does anyone have the part numbers for the revo outdrive pins as well as the jato outdrive pins.

revo - #5145
jato - #5149

Before anyone goes out and gets those pins, wait a couple days because I found some errors in a previous post about the pins...

Thanks for the info Brian!

OK, the "pin mod" post has been fixed...

Has anyone else gotten a little "binding" after this mod? It's nothing major, just a tiny bit of resistance once a revolution. I looked at all the gears, they all were fine. There was a little bit of "sawdust" in the case, mostly from the gears and using a big block, then a TZ I suppose. Brushless is gonna help! :lol:

If you're getting binding, there could be two causes that I can think of:

1) When you do the 2nd gear lock mod, the 4mm screws you use to lock the clutch may be causing an issue. I noticed that when I threaded those 4mm screws in, the end of the screw sorta "pushed" some plastic out and may get in contact with the output gear. An exacto blade is easily used to trim this.

2) When doing with the larger pin mod, you could be overtightening them. It's hard to explain what's going on, but basically they are too tight causing the gear to flex. Try backing off a 1/4 of a turn.

I didn't do the pin mod, so it must be the extra plastic. Thanks Brian.

Are you guys talking about a brushless set-up only or can this be used with a nitro engine ??

Nitro engines need the one way bearing, so no.

Pinmod V2
 

OK, after rebuilding a couple of Revo trannys now, I think I have a winning combination. I noticed that whenever a pin broke, it was right where the threads meet the shaft, so that must mean that that spot is the most stressed. So, I modified two of the stock pins so they are about 7mm long each and then threaded both screws on each side of the gear hubs so the shaft tips meet inside the shaft. Below is a pic of the modified screw pin:

http://scriptasylum.com/forumpics/pinmod5.jpg

When cutting the black FOC pins and the original chrome pins (same size, diff color), the black ones seemed to take longer to cut with the dremel, so I think they are harder.

Also, this mod has an added benefit: Since both sides are now captured, if a pin does break, the broken end won't fall out and mess up the other gears.

Each of the three shafts are different in diameter, so there is easy no "one fix for all" solution. So...

Input shaft: In the gear hub, drill out the side of the gear hub using a 7/64" drill bit to allow for the screw pin threads. Modify two of the stock chrome pins like in the picture above and screw them in. The chrome ones are OK to use here because the pins have less force being exerted on them due to the gearing.

Idler/middle shaft: Basically do the same thing as the previous step, but use two of the black FOC pins instead. The pins here need the extra strength.

Output shaft: Since the output shaft is a softer metal, and has enough diameter, drill out the shaft hole to 2.5mm and use a Revo out drive pin.

I torture tested this setup a couple days ago and it seems to be holding up better.

Actually you can do this mod with a nitro engine, but you would lose either low speed punch or some top end. So unless you're throwing a BB in there and want a low rotating mass tranny, there'd be no reason to do it.

Right, but part of the reason the one way in in the there to begin with, is so your nitro engine can "coast". Ever see how your truck rolls back after you let off the gas? That's the clutch and the one way working together to allow your drivetrain to spin freely in reverse.

It might work, but I think you're going to have problems. I know it will be more like a 1/8 scale center diff setup but since it's an actual transmission, you might see more carnage.

Yeah, the only reason to lock the tranny is to allow the motor to be used for reverse and/or braking. Since nitros don't have full power at lower rpms, first gear is there to give you low-end grunt, yet allow fast speeds when shifted in second. If you lock the tranny, you'd almost have to have a substantially larger motor to have the torque AND high speed. If you're concerned about less rotating mass; don't be. The extra gear (first) that is removed is very light and has neglible effect.

The one way bearing in the tranny is so that first gear can disengage when 2nd kicks in. The Traxxas SportMaxx was single speed and it did just fine as a basher, albeit with a 30mph top speed. I agree with Brian, no reason to do it with nitro, I was just noting that it can/has been done and works just fine, minus the drawbacks we already discussed.

Im thinking about locking my truck into 2nd, becuase I hate the feel of my truck when it slams into second. throws the truck sideways, or causes a wheelie(I cant imagine what that does to my diffs), but I want to keep mechanical brakes. Can you do that?

Sure can. Just disable reverse and brake on the ESC.

how do i make those 3 indents on the silver circle?

I started it with a dremel and cutting stone, then finished it with a small round file. Takes no time at all.

when making those half circles on 3 corners, does it have to be exactly the same place? or could i do the half circles on some other side?

Well, the half-circles have to line up with the holes in second gear...

I'm still a bit confused as to which pins I need for the pin mod. I'm pretty sure I need #5145. Is there anything else?

The output shaft can be easily drilled out to use the Revo outdrive pins. However, since the input and intermediate shafts seem to be hardened, drilling them is a chore. Besides, those shafts are already kinda small in diameter and drilling them larger may weaken them. So, I've had good luck with using the pins found in the FOC kit (they seem to be harder) and cutting the smooth pin down a little and using two for each spot, one on each side of the gear hub. This post (earlier in this thread) shows you what I mean.

So only one of the pins need this mod? Where do I get more of those FOC pins? Thanks!

You'll need 2 pins for each shaft you need to mod.

Need to know how many shafts need the mod. I can do the math from there.

I believe BrianG said the input and output shafts should modded.

His quote
Those pins replace the ones currently in the tranny. There are two places where these go; on the input gears (blue ones in the pic in the first post), and on the output gear that is on the output shaft. These pins secure the gear to the shaft.

Thanks offroader, now I just need to figure out where to get those FOC pins.

I'm having a really hard time finding more transmission screw pins for this mod. Does anyone have a part number? Thanks!

You might want to try to give Traxxas support a call. They may be able to send you a few once you explain what you are doing. Or, they can maybe supply you with a part number just for those pins.

I'll try that. Thanks

Just talked to Traxxas and they said that the tranny screw pins are not sold seperately. Which means I would have to buy the entire gear to get the pin. So 3 pins at 7.50 a pop is a bit pricey, but I'm willing to do it if necessary.