The motor mount you speak of was done long long ago in a galaxy far far away :D
http://www.rc-monster.com/forum/showthread.php?t=351
You can also see it in my avatar.

The mount pictured above is nice but may be suseptible to chassis flex. Mounting the motor to the tranny (emaxx style) is the best method IMHO. this prevents chassis flex or flex in the angle aluminum. Flex in the mount will wreak havok on your gears.

I believe the 3.3 chassis is lengthened in the front between the tranny and front shocks.

Where are the pictures?

Actually your design was somewhat of an inspiration to do mine the way I did. I just didn't like the motor as far out on the side. As far as the angle mount flex goes, that can be greatly reduced with a simple rear motor support.

Hah! I was thinking the same thing. The engine brace from the 3.3 also helps a good deal.

The new Vantage CF chasis for the 3.3 is extended in both the front and the back. That might be enough to give an XL motor clearance. :)

Hey guys,

Couple of thoughts.

1) To use the stock transmission means using a chassis mounted motor as far as I can tell. I really looked at ways to try and mount the motor to the gear box but I don't see an easy and sturdy way to do it. Love to see ideas on how you guys did it with the stock tranny if you figured it out.

2) The mount I designed could be redesigned to be pushed forward by just over .25 inches if the spacer wasn't used, I don't know however if this makes enough room to clear the larger motors, and it would require even more redesign to accomodate smaller gear ratios. It can be done but I frankly don't have time to do it unless I know there will be enough people buying them (just too many projects in the que and regular work has been killing me)

3) I looked at other ways to try and mount the motor towards the center of the chassis but it puts the motor up higher if you go over the shocks for example, and it will be difficult do this in a way that makes it sturdy.

4) I am open to ideas but to effectively machine something for these bigger can motors, I need the gears and a bigger motor. If there is a popular motor (or standard size and gear), I could work something up if there is enough interest and someone who could lend the motor/gear for a few weeks.

I welcome any comments, ideas, or thoughts.

I personally don't have an extra motor laying around, but the XL size can is almost 70mm long. The standard diameter seems to be 36mm, except for the Neu motors. The wires (if they come straight out the back) can be made to fit if the motor is rotated so they are on top.

I don't have any measurements for the mounting height of the motor since I did mine by eye (scientific, eh? :)). But I do have a couple of pictures that may help you get an idea by looking at the relationship with other components.

As far as gearing goes, the Revo has three Mod1 options: 36T (38mm Diam), 38T (40mm Diam), and 40T (42mm Diam). Popular pinions seem to be 14T (16mm Diam) to 16T (18mm Diam) Mod1. You have to subtract 2mm for the mesh when you measure the two gears together. I also have V1 of my motor mount I can donate for sizing purposes. It's not pretty, but it's the right size.

http://bgosselin.home.mchsi.com/e-re...otor_mount.jpg

http://bgosselin.home.mchsi.com/e-re...evo_v2_top.jpg

Brian your truck looks great. Are you using the revo center diff ?.

Thanks!

No, no diff yet. I bought a center diff from Squee that's basically a custom buggy diff, I just haven't put it in yet.

Lol, I just noticed there are two of the same pics above. I'll have to fix that!

Brian, thanks for the offer. I just don't feel comfortable selling anything that I can't actually fit and test with an actual motor. I'd like to think that most people wouldn't be comfortable buying something built on measurements and theory with not actual testing.

I'm confused on the length issue, my motor is 72mm in total length and I get ZERO interference with the suspension and my wires didn't have to be routed in any way shape or form. Is my chassis different somehow? If I moved the whole mount forward by .25 inches, it would easily clear any wires or anything on the back of the motor this length.

That said, the only thing I see needing to be changed to use different gears is really the amount of "throw" required to get the motor closer to the spur and accomodate smaller gear center to gear center distance for smaller gears.

Brian your motor sits visibly farther back than mine, you sure it's only 70mm in length??? :)


TypeR, thanks for posting pics and comments. If you have any issues let me know.

Interesting idea (whoever suggested it) in supporting the motor on the hind end, trying to figure out how to do this. Could be tough since motor diameters seem to vary quite a bit probably need something that adjusts....

I haven't noticed any flexing once I bolted the motor down but maybe I just didn't beat on mine hard enough yet. :D

I liked the idea of getting the motor centered on the truck and getting the batts stradled on each side, but I just can't see to visualize a way that won't introduce a ton of flex and part complexity (making the cost higher).


I apologize TypeR, and the rest, but the motor mount *is* the most expensive cuz it takes the longest to machine. Unfortuneatly, I can't seem to get it simpler. The vert piece requires a 2 decking operations, a finishing op on the lip, and three tool changes to complete before hand finishing. The lower takes two drilling operations with different jigs, 6 taps, and finishing. It takes me well over an hour for each one individually, not to mention machine wear, finishing materials, and the screw hardware/materials. There are more than 300 lines of Gcode involved in making just the motor mount and I spent about 35 hours in total getting it to be a repeatable reproduceable part (including two prototypes which are in my recycling bin).

I am not complaining, as I told brian, I make very little on these and do it mostly for the enjoyment of the hobby (cars and machining) and to cover the costs of making stuff. It also helps me show just enough income on my business to keep the IRS off my back.

That's OK, I know what you mean. It's tough enough to get things exact even with the test parts without trying to guess from pictures.

Ok, OK, I was a little incorrect about the motor length (must have been thinking of a different motor). The XL can is 74mm without the wires. Add in the RCM heatsink and the length goes up to ~79mm. Although about 3mm of that extra 5mm is the end clamp, which is not very wide and not likely to hit anything. Still, you can see from the pic of my truck that the end of the motor is quite close to the suspension arm and my motor mount is as close to the spur I can get without hitting the slipper adjustment screw. I'm using the stock blue chassis.

About the motor support; I don't think flex is an issue during normal driving, but when you take jumps, there is a fair about of weight (motor) that wants to drop when you land. Aluminum does flex and if you are on the throttle when it's flexing, the mesh isn't perfect. For support, I was thinking about wedging a piece of firm rubber between the mount and the motor. I'd probably shape the rubber so it fits the contour of the motor can. The only other place to support a Feigao/Wanderer motor with a bracket would be by using the RCM heatsink clamp screws and I don't think they were intended to be stressed in that way.

What would be the difference with the center diff vs. the Revo or emaxx tranny?

It's the center diff hop-up for the Revo tranny. The new Revo 3.3 has the option of using a center diff inside the tranny. Unfortunately, it only uses 4 spider gears, while Squee's used 6 IIRC.

I'm reading all of this with great interest, but it still seems to me that bang for the buck and ease of conversion still falls with the Emaxx tranny. But I also recognize that without people doing things like this, we probably wouldnt have converted nitros!

Hey Paul - No worries. I didn't mean to imply that the motor mount was too expensive/not worth it, I just wanted to point out for folks who want the nifty 2nd gear adapter that it's one of the cheaper parts of the kit. :003:

I'd like to see an optional base plate that is moved forward (the .25" you mentioned) to allow the pinion to ride completely on the motor shaft when using the Mod1 gears. Right now the pinion hangs off a bit.

As far as the rear brace, I've been tossing around a couple ideas. The simplest being a pedestal that could bolt to the rear of base that would be curved with the approxiamate diameter of the motor can, but not touching. And then use some kind of shock absorbing material to go in between, that would compress to the final shape.

The other idea is more complicated, and would make the use of a heatsink problematic, but would be like the Fine Designe motor mount that has a rear clamp to completely support the rear of the can.

I looked into using the Emaxx tranny, but once you buy all the stock Traxxas pieces and upgraded parts to make it work, it's much more expensive than Paul's kit (which also looks cleaner and performs better IMHO). If you already have those parts though, I can see why it would be an attractive option.

That's true, but a big downside to the Emaxx tranny is the COG is kinda high when using the stock chassis. Not to mention that the strobe is not available anymore, so other methods must be devised for the slipper.

The Revo tranny works quite well with a couple of mods and is lighter than the emaxx tranny, especially once you remove all the unecessary gears (reverse, and 1st gear). The only "tough" part is locking second gear and that seems to have several workable solutions. Also, finding a suitable motor mount seems to be a challenge, but it's been done a few different ways with success so it's possible.

I like having the motor on one side and the batteries on the other for ease of replacing them. Granted, when using NiMH batts, the weight can be a little unbalanced, but the use of lipos should really help that. Even so, I've been using 14 GP cells all on one side and haven't noticed any adverse handling characteristics.

Looks like we have a similar idea for the rear motor support. The pedestal idea may be simple, but simple is usually the better (and cheaper) route. Although instead of seperate pieces, just make the whole thing out of a firm rubber and wedge it in there. That should be even cheaper and simpler. It also would work with the slightly larger motors (Neu) since rubber does have some flex.

The heatsink clamp is interesting as well. To get around the issue of using the RCM heatsink, just machine it such that part of the clamp replaces the RCM heatsink bar.

Well, I was at the track today and I once again broke one of the little pins that hold the gear to the shaft (internal to the tranny). Is there a stronger replacement for this? It's the pin in the lower right corner in the picture below (borrowed from buytraxxas.com).

http://www.buytraxxas.com/images/products/5396.jpg

Other than that, the tranny is holding up well. All the internal gears show little or no wear and the locking mechanism (v2) works well.

Brian, did you ever install the center diff?

Dang it! I knew I forgot something, and I just had the tranny apart too! :007: :007: :035:

Good point squee,
The center diff should releave some of those big bursts of stress on the tranny parts.

I agree on the center diff and relief of stress. It should make tranny last better.

The sad about this is that I got a custom center diff from Squee a while back (uses buggy diff), but keep forgetting to put it in everytime I have the tranny apart.

Put a yellow note on the gearbox..

It shouldn't take but about 20 minutes to do...If that.

lol, yeah, or tie a string to my finger...

I know it doesn't take long, but I don't like to take things apart unless I need to as the threads get worn. Besides, I was just looking at the diagram that it came with and I think either something is missing or something doesn't fit quite right. I'll take a better look sometime...

OK, I decided to disassemble the tranny and install that custom center diff. Wow, what a PITA!!!

I slapped 'er in per the instructions and as soon as I assembled it, there was binding somewhere. Loosening the tranny case screws half a turn fixed it, but that was not a viable option.

I took it back apart and saw that the shim that goes on the gear side of the diff was bent due to some raised areas on the blue gear. So, I shaved off the little lumps on the gear so the surface was flat. Then, I put the Al shim on my vice and hammered it flat again. Of course, being aluminum, this spread out the shim so I had to do some precision dremelling (is that even a word?) to get the shim back into the right shape.

About an hour and a half later, and re-arranging the various thickness shims around, the center diff is installed and turns freely without binding or front to back movement. Obviously, I have yet to try it in real-world conditions, but I expect to be pleased since it's a modified buggy diff.

No pics of the diff in trannsy. Oh why?

Hmm...Sounds like a PITA...I never had any troubles at all...It went in as easy as possible...

Well, because I thought it's not really interesting. I mean, there are plenty pics of the Revo trannys around and only the diff was added. This allows you to use your imagination. :)

Please don't leave any room for my sick imagination Brian.. I'm begging you.. :p

OK, everyone can use their imagination except Serum - and other like-minded sickos. :005:

Thanks Brain..

I aim to please. :)

A little update showing Mike's new motor mount installed in my Revo:

http://scriptasylum.com/forumpics/revo_mount_1.jpg

http://scriptasylum.com/forumpics/revo_mount_2.jpg

http://scriptasylum.com/forumpics/revo_mount_3.jpg

http://scriptasylum.com/forumpics/revo_mount_4.jpg

Very solid and installed with absolutely no trouble or issues.

Looks great....

looks great, hope mike made lots of these

Looks great indeed. Hope it works well fro you. Man... I really need to get some money and build a revo. :027:

Nice :004:

I ran it around the yard a little today and took a couple of smallish jumps and everything still seems solid. I never really had any problems with my old mount but it would flex slightly when I pushed firmly on the back of the motor. This mount doesn't do that. So, if something is flexing, it's GOTTA be the chassis.

I'm sure it happens but it's going to take a lot to flex a stock chassis enough to notice something like spur/pinion grinding. So do you got some pictures of the whole truck?

Yeah, there's a link in my sig "My Brushless Conversion"...