My Brushless Revo Bolt on conversion kit

Since I have a small machine shop (2 cnc mills and a cnc lathe), I set out to build a BOLT ON KIT that could be sold for less than 100 dollars in a retail setting, that would allow for a brushless drop in conversion (I know some of you will scoff at the novak setup but it was the cheapest and easiest conversion motor combo I could find).

Problem 1: Gearing (yea I know you all went through this too)
The stock gearing (like all nitro cars/trucks from my understanding) was metric to begin with, all the stock stuff is Mod 1 Metric teeth. I checked into my gearing and drive supplier catalog but couldn't find an easy way to adapt a metric gear to the Novak motor shaft (or any standard 540 motor shaft for that matter). I decided to do an 'end around', time to change the stock spur gear. After some messing around and searching, I found a suitable SAE pitch gear that Associated makes, and quite incidentally, it has three molded holes that were almost a perfect match to the 120 degree bolt pattern on the slipper!
So we keep the slipper (good thing IMHO), and now I had to just machine an adapter/spacer to get the gear mounted flat, (after 3 or for stripped gears I finally got one machined/sized correctly and now it is solid).

The second issue within the gearing adventure was that the gearing inside the gear box needed to be locked in a manner that would stand up to the torque and abuse of driving an overpowered electric vehicle. I tried the long bolt in the centrifigal clutch unit trick but the click clacking and not so instantaneous engagement pissed me off after a few runs. I also eventually stripped the screw off and then the steel stoppers molded into the gear.

Locking the reverse shifter was very simple, a nicely bent piano wire and a bolt took care of it. I used the Emaxx overall G/R on a Novak system as a guide and after lots of math, I settled on the second gear gear ratio and the associated gear and a 14-19 tooth pinion.

I then broke down and machined an ALU replacment hub for the second gear gearing (replacing the one way bearing hub completely and bolting into the gear). I completely ditched the first gear, and with the locking hub, the electronic braking and reverse work perfectly. Works like a Charm!

Problem 2: Motor mounting
So I started with a hybrid motor mount of carbon and aluminum, the carbon gave too much flex and I went to an all aluminum machined two piece motor mount which allows gear ratio and mesh adjustments. It bolts into the stock engine location as you can see in the pictures on my site.

I then designed some simple 2mm carbon fiber trays that bolt into stock bolt holes on the chassis for the battery and ESC, and its done.

Performance:

Holy cr*p! I ran a 14 cell (cheap 3000mah NiMHs) and then a 4s2p TP prolite setup it will wheelie on any surface even easing into the throttle, and is visibly faster than the nitro setup I had on my stock revo. I had removed all of the nitro workings including the throttle and shift servos, the rx pack, the plastics for them all, all the braking components, etc.

The verticle CG remains very much the same, so the handling of the truck (other than off the line grunt which was not even close in the nitro setup) is very much the same. I went to stiffer springs in the rear to better support the battery weight and keep the ride hieght higher for my personal bashing terrain and tastes but other than that the machine is pretty much stock.

(and now the best part)

Price: The conversion kit is 74.99 retail, and yes I will sell individual parts if you want them, see www.eaglesviewaerial.com/products.html for the kits. The only things you need to complete are BL motor, batteries of your choice, and a 14-19t pinion gear from Traxxas (from the Emaxx line).

Ok ok, pics, I can't post em because I took them in high quality format and don't have any of my image tools with me, check the website for detailed pics.

PLEASE NOTE THAT THE CARBON PORTION OF THE MOTOR MOUNT IN THE PICTURE IS NOW ALUMINUM....
(sorry, been out of town, need to shoot pics of the new mount piece).

I will post videos of it shortly, check my website for more details....
If you have questions or want parts machined, please let me know, I will try and do a run of hubs this weekend feel free to call me or IM/email with questions (ph:847-778-0874)

[Sneeck]

Very nice kit. Just a head's up, but Mike has the mod 1 pinion's w/ 1/8th shaft.

[Serum]

You made a nice conversion, But if i may be so free to criticize; (please don't take me wrong)

I would only use it with lipo's, because with heavy nimh cells, the balance will be gone. With the 4S2P packs you are using it already is out of balance.

That batterietray doesn't support the batteries to fall out in front or in the rear, with bashing you really want your cells to be put on tighter than tight.

The speedo is placed on a forbidden spot, it is a treasure, you want it well hidden for impacts. if you crash your conversion like this, it will be bye bye speedo if it took a wrong hit.

Have you seen this sexy conversion?

I have seen a movie of the hvmaxx on 4S lipo, and i sure was impressed! in fact; i am thinking about buying one for a lightweight bashmaxx. It is one nice setup. About the gearing, i think you are smart enough to look up the used gears, and calculate the gearing ratio. Without the pinion/spur the gearing ratio of a stock e-maxx is 5 to 1. and the advice Novak gives on their site can be used on your revo too.

Sorry for being so hard on you, it isn't my intention, but i think when you sell something it needs to be perfect, don't you agree?

Daniel did a perfect conversion on his revo, it uses the stock maxx transmission. (which gives you a nice 2 speed and a motor brake)

You might consider using the mechanical brake, it will be even quicker with the 2 speed and the mechanical brake will be easier on your controller as well. (so the controller gets less hot)

Again, sorry for being so straight forward..

Hey feedback is welcome, I appreciate the thoughts.

I love the gorilla max setup btw, I have a lot of respect for the designer and looking at the bits as a machinist, the cost is totally justified. I just can't bring my self to bash a rig setup with something that nice on it...



Couple of things.

1 Yes I agree that the speedo is in a place I am not crazy about, I am working on a mount that will put it up in the front just over the rear of the shocks, plan was to offer it free to any who bought the original kit, cost of the carbon for the plate is minimal, the motor mount and tranny lock were the harder bits.

2 Batteries flying is not a problem when you velcro the crap out of it, I use velcro on the bottom of the batts, and pull the straps tight (unlike in the pic), and I have had zero probs with them sliding. That said, I agree it would be nice to have a pan there but it could significantly increase the cost. Well,
wait...

Idea! I know bling is king but I could probably machine a battery 'tub' from delrin pretty cheaply, something one piece possibly, shouldn't really increase the cost too much, would the possibly users of a kit like this scoff at delrin plastic instead of carbon plates?

3 Balance. (just to credentialize, I am an aircraft guy first so I am sensitive to this more so than many), are we talking about lateral or for/aft CG on this thing? The batts in Nimh form were mounted fairly far forward on that plate, and the for/aft balance was darn close to the back of the transmission is that too far back? If you are talking about lateral balancing, the ESC and motor are only 3 oz less (and mounted on the opposite side) than the two Nimh packs I had in there so lateral balancing wasn't really a problem for me, are you suggesting that 3oz is a prob? I am not an experienced racer so I wasn't able to feel much handling difference but I could be off base, give me some guidance.

The metric pinion gears are not a problem for me now, didn't have the lathe when I did this, now I can bore any steel pinion to the diameter I want (just doing a reaming operation on it). So I should be able to support any motor shaft size. Gear I found along with the alu mount for it are actually cheaper to buy than most of the reasonably sized metric gears I was able to find on my source.

Gear ratio, I worked backwards, I used the basic recommendations from Novak as the target, I used the knowledge from Traxxas site of what the 2nd gear ratio was, divided out the stock pinion to spur ratio, and multiplied back in the new pinion to spur ratio. I have it pretty much right based on motor temps, current loading, and general speed and torque.

As for the mechanical brake, I didn't like dealing with the reverse shifting and braking stuff, it was purely choice, I had no need for the second gear and I prefer the electronic braking. You could easily keep these components in and just use a motor mount too.

ANyhow thanks for the feedback and the idea, I might try some stuff with delrin to see what I can come up with instead of the carbon plates...

[BrianG]

That's pretty cool. I too have some comments:

- Tranny locking. I don't really know what you mean by using piano wire, but the way I locked mine seems to be quite effective: http://www.rc-monster.com/forum/show...3&postcount=23. I know you might have seen this already since you posted a reply in that thread.

- Mod1 Gears. As pointed out before, Mike offers Mod1 pitch pinions and traxxas offers stock 36, 38, and 40T spurs which are Mod1 as well. Due to the fact that the 1mm pitch is a bit stronger than other pitches, I would think that you would go with that simply for durability. This would negate the need for the milled adaptor that goes on the slipper assemby. Plus, the stock Revo spur seems to be wider which would help distribute the force across more tooth surface area.

- Gearing. In my locked tranny, I decided to remove first gear and install the wide-ratio gear set. This gearing is still lower than an e-maxx tranny, so it makes up for the relatively low pinion/spur ratio when using the stock 40T revo spur. A little while back, I created an online R/C speed calculator that takes the various gear ratios into consideration: http://scriptasylum.com/rc_speed.html. There has been some debate over the accuracy of the final speed, but the gear ratios are correct. You can select from several known transmissions and such to see the relative difference.

- Battery placement. I like your overall design, but I was planning to make trays that would fit underneath the truck. That would really lower the CG and allow you to equally balance the truck. However, this would reduce the clearance by about 3/4" over stock, but frees up a lot of space on top of the chassis to install the ESC (even is a box to protect it better). The reduced ground clearance might make it better suited for racing primarily.

Can your motor mount be adjusted horizontally? It looks like that milled piece pushes the spur further back, but if I don't use it, the pinion will fall short. If the motor can slide forward a little, it would solve that problem (for me anyway).

Hey Brian thanks for the comments!

In answer to your questions...


- Tranny locking. I don't really know what you mean by using piano wire, but the way I locked mine seems to be quite effective: http://www.rc-monster.com/forum/show...3&postcount=23. I know you might have seen this already since you posted a reply in that thread.

I just bent a piece of piano wire, put it in the shift input hole (where the shift shaft sticks out of the transmission) and then bolted it to the transmission case so that the shaft wouldn't slide, this keeps it from sliding in and out of reverse/forward. Very simple really.


- Mod1 Gears. As pointed out before, Mike offers Mod1 pitch pinions and traxxas offers stock 36, 38, and 40T spurs which are Mod1 as well. Due to the fact that the 1mm pitch is a bit stronger than other pitches, I would think that you would go with that simply for durability. This would negate the need for the milled adaptor that goes on the slipper assemby. Plus, the stock Revo spur seems to be wider which would help distribute the force across more tooth surface area.

I can tell you from experience that strength of the gear between a mod1 vs a 32 pitch gear is negligible. The milled adapter serves one primary purpose, to allow the gear to be mounted FLAT to prevent the plastic from buckling and providing an uneven fit. It really reinforces the plastic center of the gear, not the teeth. I have worked with a number of different gearing systems in the heli's i have been designing (mostly 1500 watts and up) and can tell you with confidence, if the fit isn't right, the mod1s will strip just as quickly as the 32 pitch teeth, They are pretty close in size and relative strength.

A wider gear however is stronger for the reason you stated above, that part I agree with, what I found was that in practicality, if you set the gear mesh right and have the motor mount rigid, and have the gear mounted firmly, it makes very little to no difference at all between them. Also, the gear I am using is a 52 tooth gear, I went down the traxxas spur gear line of thinking but they didn't have a mod1 gear big enough for the gear ratio I was shooting for assuming that the 2nd gear stock ratio was the prefered starting point. The 2nd gear ratio starting point was preferred because it made things easy to lock up within the transmission, (the hub was easier to machine for that particular fit).
Basically this is a case of one thing affecting a lot of other things, but either method seems to work pretty well. Good points.

- Battery placement. I like your overall design, but I was planning to make trays that would fit underneath the truck. That would really lower the CG and allow you to equally balance the truck. However, this would reduce the clearance by about 3/4" over stock, but frees up a lot of space on top of the chassis to install the ESC (even is a box to protect it better). The reduced ground clearance might make it better suited for racing primarily.

This is one of those things that everyone seems to like something different. What i like about your setup is that it is sleek, the only thing I hate about mine is the girth of the vehicle now. YOu have a nice clean look to the sides and top of your setup. Problem I had is that I wanted to keep the ground clearance as high as possible without changing the vert cg too much, as stated before I am a basher, not a racer. For racing I really like your setup better, I guess it would be pretty easy to offer an either or type setup to make everyone happy, no?

My motor mount does not slide forward, but I could easily just redesign the lower motor mount block to add another .5 inch of spacing, it is quite simple to do, CNC makes machining changes so easy it is sick!

I am intrigued enough by the idea of doing machined delrin tubs that I am ordering some 3 and 4 inch thick black acetal copolymer (prestressed delrin) stock to try some prototypes in the next week or two. I wish I was home during the week to do more of this stuff!

[BrianG]

Thanks for the replies.

I hear what you are saying about the gear pitch and fit. This is where a SOLID motor and tranny mount is imperative. Any flexing or twisting will change the mesh and will strip anything. Still, I think I'll stick with the Mod1 spur, if only because they are easy to get at my LHS since they are stock Traxxas parts.

My stumbling block is the part you have nailed down: the motor mount. If that was available seperately, adjustable vertically, adjustable horizontally (to bring the pinion laterally closer to the tranny), and in 3mm-4mm thick aluminum, I'd definitely get one if the price was reasonable. Basically; a univeral mount that will mate the motor pinion with the stock spur -or- your milled spacer/non-standard spur combo.

"My design" as you put it isn't even off the ground yet. I was waiting for parts for finish a current Revo design and I had an extra chassis, so I started messing around with a design that uses more stock parts (easier availablilty locally). I have plans for it, but I ad kinda halted until I could get a motor mount designed. Making things with Lowe's aluminum stock on a vise is difficult to do accurately. :)

No reason we can't join forces, I am not proud dude!

The motor mount is available separately now, with or without the milled spacer. Mount is 25 plus shipping, spacer is 8 bucks plus shipping. Making it adjustable horizontally may take some redesign, let me chew on it for a few days, maybe the answer will come. 2nd gear lock hub is 20 plus shipping. Obviously you only pay one shipping charge if you order more than one part.

Just so you guys understand, I am not making a fortune on these nor do I expect to, that pricing barely covers the tooling and material, basically I am making about 5 bucks an hour doing these parts (less than most fast food employees). In other words I am doing it for fun since I can piggy back it on my other business (don't tell the IRS I wrote off all the CNC stuff this year).

The current mount is milled from quarter inch (6.35mm) aluminum stock drilled tapped and countersunk, and has a natural finish. It uses M3 screws (3mm metric socket head) and is very stiff.

The spacer/mount is made to work with the stock slipper.

Again I am available by phone to chat if you have any questions.

Also if anyone wants custom CNC stuff done, I am willing to do prototyping VERY cheap if you are any good with CAD...

BTW Brian, I can almost guarantee that the Team Associated gear I am using is available at your LHS, it is from a nitro TC3, (52 or 54 can't remember which off hand 32 pitch gear). I will get the part number when I get home. Every shop that I have been to that sells cars, has this gear, it is a popular part.

[squeeforever]

nice! i like it. however, you could have saved ALOT of pain and just went with a jato spur gear. there mod .8 and mesh up perfect to 32p, not to mention it would just bolt right on.

[crazyjr]

Originally Posted by squeeforever

nice! i like it. however, you could have saved ALOT of pain and just went with a jato spur gear. there mod .8 and mesh up perfect to 32p, not to mention it would just bolt right on.

true but they are a little smaller than the Revo gears

[Batfish]

Originally Posted by crazyjr

true but they are a little smaller than the Revo gears

I bought Revo gears to try on my Jato conversion. The 40 tooth Revo gear is just about the same size as the 48 tooth Jato gear. I ended up using the Jato gear because the .8mod is almost exactly the same as 32 pitch. .8mod is 31.175 imperial (I read that somewhere). I ran a Robinson 32pitch gear against the 48 tooth Jato gear for a couple months with no noticeable wear on the spur.

b0gh0s,
First - Welcome to the forums!

Second - This is a nice project at a reasonable cost. I would have the same concerns regarding ESC and battery placement that have been mentioned earlier.

Lastly - RC-Monster hosts these public forums as a means for our members to collaborate on ideas and discuss vehicles and projects. We ask that you not use it as a means for selling your product. You are free to discuss your product and refer people to email, PM, or your own website for further details regarding sales, but please refrain from posting sale information here.
Once you are at a final design (and our gurus here like the overall product) maybe you should talk to Mike (RC-Monster.com owner) about the possibility of selling your product as a dealer. You're welcome to email him at mike@rc-monster.com

All the best to your efforts and welcome aboard!

Thanks Joe! Thanks to all for the welcome btw, this is a cool group and everyone has been pretty nice so far.

I always try to respect the forum rules (going forward I will not post pricing information in the future, sorry). Just to reiterate my intentions, as I stated above, I am not expecting to make any money off this stuff (no one I know really does) but rather just have some fun and make a product that I can sell for a price that will actually offset the cost of making it. I just enjoy designing and building stuff. (and breaking it too). I would be happy to get Mike dealer quantities and pricing, if he can make a margin on it, god bless!

As for the Jato gears, sounds like a good idea, the only problem is that if I go much smaller than 50 teeth, I run into problems finding appropriate pinion gears small enough to hit the target gear ratio range. One of the reasons I went to another brand of gear and went through the trouble of making the gear offset mount is that it makes finding and trying pinion gears easier (much easier access to pinions sizes 14-20 in my LHS experiences than finding 4, 5, and 6 tooth pinions). Again, this associated gear is really popular, and is only 3 bucks per gear typically. Cheap, easy, and accessible.

Squee,

That avatar is killing me! :D

[Serum]

We are complaining about that avatar for over half a year now, he doesn't seem to get the hint.. :p