Questions about Revo 3.3 to electric conversion

[corneileous]

Yes, and with the Max8, you would have more room to grow, like maybe if you later decided to use it in a heavier rig. But as was mentioned, your drivetrain may not handle 4s, at least without doing some upgrading.

OK, and even though this question may be more or less better suited for @SpareParts but what upgrades could I do being that I’m probably pretty limited on what I could do unless I just get even deeper in the customization part? It’s been 10 years since I’ve at least seen my front and rear diff but as I mentioned earlier, I do know that Traxxas has upgraded ring and pinion gears that aren’t cast that are actually made of machined steel. And who knows, hot racing, Integy, GPM, or some of those other aftermarket RC parts companies might have some stronger diff kits as a whole that I could probably look into but being that it was said the transmission was also one of the weak points, I guess someday I could think about upgrading from the stock plastic case to an aluminum one. I could probably even upgrade to aluminum front and rear bulkheads as well without hopefully adding too much weight.

 

[SpareParts]

Haha yeah I am still using the mechanical brake because I think it is neat. On the trail truck I am running it entirely like a nitro with the mechanical brake and the reverse gear.

I run 3s because I have a lot of 3s batteries and 4s just gets me in trouble. I suppose you can probably gear it for 50mph; those speeds aren't unreasonable for a nitro revo after all, but again the main difference is a nitro motor doesn't go from 0-50mph instantly. Turn your punch down and drive reasonably. If you have 4s batteries already just use those and gear it reasonably.

On the revo conversion I have an old Tekno conversion kit that came with the motor mount, battery tray, esc mount on the transmission, and the receiver box. On the trail version I have a cheap ebay motor mount and a hunk of kydex as a battery tray.

For ESC location, I would say wait until you figure out your battery tray and battery size, then try to even out your weight distribution as much as you can with the esc. With a 4268 motor on the back left, and a 4s battery on the back right, you'll probably want the esc on the front left. Unless you have some crazy beefy servo that weighs a lot, then maybe the steering servo on the left. In any case it isn't an ideal weight distribution but it also isn't that terribly different from 8th scale buggy layouts.

The rear chassis support thing is Traxxas part 5632. It was kind of a tight fit on the nitro, not sure if the spacing is slightly different on the summit/erevo. I actually got it to use as an esc mount but I didn't like it for that purpose.

I was curious how the max10 g2 system really did. I had the max10 sct/3660sl in my stampede for a while on 3S and the motor ran hot as did the esc. I ended up moving the esc to my eJato with a 3665/3100kv and it does really well in that. I got a slash chassis for the stampede and a mild 1/8th system on 4S in it... and a lot of other upgrades to deal with that. lol!

What motor mount do you use for the conversion? Homemade or something else?

FWIW, the first brushless e-revo had similar diffs to the nitro's, but not fully the same. Similar ring/pinion gear/housing/bearings, but the cup was different as it had steel inserts for the x-pin and the "i-bar" to try and beef it up. They held up well to 4S with the MMv2/1515 2200kv system in the v1 e-revo. Some guys even replaced the input bearings with oillight bushings and ran 6S without issue... long thread on traxxas.com. I'm surprised the internals held up... regardless, when I decided to run 6S, I got a 2.0 roller and move stuff over that I could and never had an issue with the drivetrain with 6S then.

True, the erevo v1 diffs and later slash 4x4 diffs were improved with the I-bar. That can easily be added to the nitro revo as well. I think the parts are fine as long as you don't drive like you're trying to break it.

If you go back through the forums for these brushless conversions from like, 2004-08 there is a lot of great info but they pretty much all end the same way; Once the erevo came out, everyone sold their conversions and bought an erevo. There are limitations to this conversion without a doubt.

I too converted my stampede 4x4 to a slash 4x4. And then I had enough parts to rebuild the stampede again! I have 3660 motors in most of my 1/10 trucks and I don't see much heat. I think I gear my trucks far more conservatively than most; if it is getting hot then I gear down. I like long run-times and durability. I have 8th scale buggies for more speed but I don't run them much.

 

[olds97_lss]

True, the erevo v1 diffs and later slash 4x4 diffs were improved with the I-bar. That can easily be added to the nitro revo as well. I think the parts are fine as long as you don't drive like you're trying to break it.

If you go back through the forums for these brushless conversions from like, 2004-08 there is a lot of great info but they pretty much all end the same way; Once the erevo came out, everyone sold their conversions and bought an erevo. There are limitations to this conversion without a doubt.

I too converted my stampede 4x4 to a slash 4x4. And then I had enough parts to rebuild the stampede again! I have 3660 motors in most of my 1/10 trucks and I don't see much heat. I think I gear my trucks far more conservatively than most; if it is getting hot then I gear down. I like long run-times and durability. I have 8th scale buggies for more speed but I don't run them much.

I didn't know they put ibar's in the slash. Kind of odd considering the lack of grip those things have over the stampede. Would make more sense if they put those kinds of diffs in the hoss with the larger motor it has and more grippy tires. I run tires similar to those on my slashpede 4x4 (still HCG) now. Just the 17mm version from the maxx with +10mm 12->17mm hubs on my mip x-duty's since they key their hex to the axle vs using a pin.

I had mine geared kind of tall, but was running 2.8 trenchers at the time and I spend a lot of time bashing in the grass at a grass bmx track. Although, at the time, it was overheating on me at the skate park... probably just too tall of gearing. With the blx185/blx4074 2050kv in it on 4S... I rarely reach WOT in the thing now as it likes to take flight at those speeds. But I can run pack after pack in it without overheating and keep pace with my buddies when they are running their 6S trucks.

I still have 2 nitro revo's that I almost never drive. If either still had a 2.5R or 3.3 in it, I'd consider converting one to brushless, but one has a big block and the other an OS21TM. Both with fully RRP steel transmissions. Haven't driven either in a couple years though... just too easy running my brushless stuff. Still fun to break one out once in a while though and run 500cc's through it.

 

[SpareParts]

I didn't know they put ibar's in the slash. Kind of odd considering the lack of grip those things have over the stampede. Would make more sense if they put those kinds of diffs in the hoss with the larger motor it has and more grippy tires. I run tires similar to those on my slashpede 4x4 (still HCG) now. Just the 17mm version from the maxx with +10mm 12->17mm hubs on my mip x-duty's since they key their hex to the axle vs using a pin.

I had mine geared kind of tall, but was running 2.8 trenchers at the time and I spend a lot of time bashing in the grass at a grass bmx track. Although, at the time, it was overheating on me at the skate park... probably just too tall of gearing. With the blx185/blx4074 2050kv in it on 4S... I rarely reach WOT in the thing now as it likes to take flight at those speeds. But I can run pack after pack in it without overheating and keep pace with my buddies when they are running their 6S trucks.

I still have 2 nitro revo's that I almost never drive. If either still had a 2.5R or 3.3 in it, I'd consider converting one to brushless, but one has a big block and the other an OS21TM. Both with fully RRP steel transmissions. Haven't driven either in a couple years though... just too easy running my brushless stuff. Still fun to break one out once in a while though and run 500cc's through it.

Ah yes, I forgot about tires! Good traction will definitely lead to more heat. I like crappy slippery tires so I can drift around in the grass without traction rolling. That's why the rock hard talons are so excellent on my 3s revo.


I thought the Slash ultimate or platinum or super duper came with the I-bar, but maybe not. It was just such a common upgrade.

 

[Greywolf74]

I watched a video on this a little earlier today about gear ratios so if I understand this correctly, you’re saying between the motor pinion gear and the transmission spur gear, I can go with whatever I want as long whatever I go with, the pinion gear makes 2 and a half revolutions to one complete rotation of the spur gear, correct?

Yes, thats correct. or you could look at it as the spur will have 2.5 times more teeth than the pinion. For example if your pinion has 10 teeth then your spur would have 25T. I just used those number for the sake of keeping the math simple but lets say you had a 54T spur and you wanted to run a 2.5:1 ratio. You just divide the 54 by 2.5 which gives you 21.6 so you could start with a pinion somewhere around 20-22T depending on what you have handy. It doesn't have to be exact. If the closest thing you have is a 18T then run that.

Whereever you start out at keep a close eye on ESC and motor temps (160F max) and if your electronics are getting too hot then step your pinion down or make your spur bigger. If the motor is way cool after a full pack then consider stepping up to a bigger pinion or smaller spur.

 

[corneileous]

Yes, thats correct. or you could look at it as the spur will have 2.5 times more teeth than the pinion. For example if your pinion has 10 teeth then your spur would have 25T. I just used those number for the sake of keeping the math simple but lets say you had a 54T spur and you wanted to run a 2.5:1 ratio. You just divide the 54 by 2.5 which gives you 21.6 so you could start with a pinion somewhere around 20-22T depending on what you have handy. It doesn't have to be exact. If the closest thing you have is a 18T then run that.

Whereever you start out at keep a close eye on ESC and motor temps (160F max) and if your electronics are getting too hot then step your pinion down or make your spur bigger. If the motor is way cool after a full pack then consider stepping up to a bigger pinion or smaller spur.

That makes sense. Thank you for explaining that.

Well after seeing my Revo- I’ve been outta town all week but it did have a 38t spur originally and a 15T clutch bell and when I updated it to modern Revo 3.3 specs with bigger tires, I put a 14T bell on and some time after that I pulled the 38T spur off and put on a 40T as that’s what’s on my transmission now.

I found this calculator and according to it, the 15T/38T combo was a 2.53:1. When I changed to a 14T bell, that put it at 2.714:1 and going from the 38T spur to a 40T spur with the 14T bell, now it’s 2.587:1.

 

[corneileous]

Haha yeah I am still using the mechanical brake because I think it is neat. On the trail truck I am running it entirely like a nitro with the mechanical brake and the reverse gear.

Oh ok, I wasn’t even sure you could use the mechanical brake with it battery power but I guess if your radio has the switch to run the servo then that answers that…lol.

I run 3s because I have a lot of 3s batteries and 4s just gets me in trouble. I suppose you can probably gear it for 50mph; those speeds aren't unreasonable for a nitro revo after all, but again the main difference is a nitro motor doesn't go from 0-50mph instantly. Turn your punch down and drive reasonably. If you have 4s batteries already just use those and gear it reasonably.

So what would you consider reasonably on a Revo 3.3 on 4S? As I was telling the other guy who explained gear ratios, this truck came originally with a 15T clutch bell and a 38T spur. When I wanted to run bigger tires and pretty much just bring it up to modern Revo 3.3 specs, I upgraded to a 14T bell because that’s what the new Revo's come with standard.

At some point I went from the 38T spur to a 40T.

On the revo conversion I have an old Tekno conversion kit that came with the motor mount, battery tray, esc mount on the transmission, and the receiver box. On the trail version I have a cheap ebay motor mount and a hunk of kydex as a battery tray.

It woulda been nice to have that kit but like you said, when the E-Revo came out, I’m sure less and less people were buying that conversion kit for their nitro Revo.

I bought a Integy motor mount and for the battery tray, receiver cover and ESC, I’m just gonna fabricate my own stuff out of 1/8th inch aluminum plate. I have a Tractor Supply nearby and they have a neat little bin that has small aluminum angle iron, square tubes and all sorts of stuff. I also bought a little box of assorted M3 and M4 screws and locknuts and my local
Hardware store has some M4/M3 drills, taps and dies for making custom screw-together stuff. I’ve already built my receiver box mount. Turned out pretty nice.

For ESC location, I would say wait until you figure out your battery tray and battery size, then try to even out your weight distribution as much as you can with the esc. With a 4268 motor on the back left, and a 4s battery on the back right, you'll probably want the esc on the front left. Unless you have some crazy beefy servo that weighs a lot, then maybe the steering servo on the left. In any case it isn't an ideal weight distribution but it also isn't that terribly different from 8th scale buggy layouts.

Yeah, I plan to put my battery box on the right rear side where the fuel tank was and I was originally gonna put the ESC between the front of the transmission and the rear front shock mount if it would fit but now that you mention it, being that I’m only going to run one servo which is the Traxxas 2075X- which I believe is the upgraded version of the metal-gear high-torque servo for the Traxxas crawlers, I’ll probably do like you said and put the ESC where the left side steering servo was if it will fit and not stick out to far laterally from the motor mount and my new servo will go on the right side.

The rear chassis support thing is Traxxas part 5632. It was kind of a tight fit on the nitro, not sure if the spacing is slightly different on the summit/erevo. I actually got it to use as an esc mount but I didn't like it for that purpose.

Oh ok.

 

[corneileous]

@Greywolf74, today when I was figuring out which spur/pinion combo to use on my stepson’s 1/16th scale E Revo, the manual had a chart that showed what the final drive ratio was depending on what tooth pinion and what tooth spur you used which also showed what the final drive ratio was for the stock pinion/spur and what the pinion/spur combo was for the high speed runs with dual batteries in a series. It also explained how that was calculated by saying to take the number of spur gear teeth and divide that by the number of pinion gear teeth and then said to take that answer and multiply it by 5.04.

I looked in the owners manual for my Revo and couldn’t find that FDR so, on my stepson’s Revo, how did they come up with that 5.04 number?

 

[corneileous]

Well I found these. I wonder if they are as good as the price reflects…

https://www.ebay.com/itm/1754530500...ar=474758659325&widget_ver=artemis&media=COPY

 

[Greywolf74]

@Greywolf74, today when I was figuring out which spur/pinion combo to use on my stepson’s 1/16th scale E Revo, the manual had a chart that showed what the final drive ratio was depending on what tooth pinion and what tooth spur you used which also showed what the final drive ratio was for the stock pinion/spur and what the pinion/spur combo was for the high speed runs with dual batteries in a series. It also explained how that was calculated by saying to take the number of spur gear teeth and divide that by the number of pinion gear teeth and then said to take that answer and multiply it by 5.04.

I looked in the owners manual for my Revo and couldn’t find that FDR so, on my stepson’s Revo, how did they come up with that 5.04 number?

In order to come up with the FDR everything in the entire driveline is taken in to account. pinion, spur, all the gears in the transmission or center diff (minus spider gears), all the gears in the F/R diffs (minus spider gears). Traxxas knows all of that info and they came up with that formula. There are calculators online that can help you come up with the FDR and you can even take it a step further and use the diameter of the tires to calculate rollout too but I never found those values to be particularly useful to me as a basher. As a basher all I care about is making sure my pinion/spur ratio is the lowest it can be without overheating my electronics.

Well I found these. I wonder if they are as good as the price reflects…

https://www.ebay.com/itm/1754530500...ar=474758659325&widget_ver=artemis&media=COPY

That I couldnt say.

 

[WickedFog]

...all the gears in the transmission or center diff, all the gears in the F/R diffs.

The gears in the diffs don't have anything to do with the drive ratio. They are just a means to transfer power from one side of the axle to the other.

As a basher all I care about is making sure my pinion/spur ratio is the lowest it can be without overheating my electronics.

Same here. I usually look at stock gearing and take a stab at it by adjusting tooth counts according to any modding I've done and test temps. There is no way to know what the best gear is by using a calculator, unless you are some super genius and can account for all the factors that come into play, like weight, motor kv, motor hp and torque, ambient temp, surface traction, drivetrain friction, power loss in the electrical connections, etc. I not that smart.

 

[Greywolf74]

The gears in the diffs don't have anything to do with the drive ratio. They are just a means to transfer power from one side of the axle to the other.

I could have sworn that the FDR calculators I've seen online have you plug in diff gears also but I could be wrong. I dont mess with those numbers so I might be misremembering

 

[WickedFog]

I could have sworn that the FDR calculators I've seen online have you plug in diff gears also but I could be wrong. I dont mess with those numbers so I might be misremembering

The ring gear on the diff, yes. But the spider gears don't have any effect on the drive ratio whatsoever.

 

[Greywolf74]

The ring gear on the diff, yes. But the spider gears don't have any effect on the drive ratio whatsoever.

oh yeah, you're right, I wasn't referring to the spider gears, thats just for slip. I was referring to ring and pinion in the diffs. Poor choice of grammar in my previous statement.

 

[corneileous]

In order to come up with the FDR everything in the entire driveline is taken in to account. pinion, spur, all the gears in the transmission or center diff (minus spider gears), all the gears in the F/R diffs (minus spider gears). Traxxas knows all of that info and they came up with that formula. There are calculators online that can help you come up with the FDR and you can even take it a step further and use the diameter of the tires to calculate rollout too but I never found those values to be particularly useful to me as a basher. As a basher all I care about is making sure my pinion/spur ratio is the lowest it can be without overheating my electronics.

Well at least one thing about it, changing spurs and pinions on my Revo 3.3 nitro to brushless conversion should be fairly easy so maybe I should just quit overthinking this and just go off of what my infrared temp gun says when I get it running. Although I’ve never been very good at math, I was just trying to figure out a baseline using numbers.

But OK, if that 5.04 number is everything in the drivetrain, are they just essentially taking whatever the gear ratio is in the diffs and adding it to whatever the gear ratio is between the output shafts and the input shaft of the transmission? Is that where that 5.04 number came from? One thing about it, that 5.04 number is not the same on the different cars. On my Traxxas max it’s 5.69 but for some reason, the gear chart in the owners manual for my max doesn’t tell me whatever that number is when you take the number of spur teeth, divide it by the number of pinion teeth and multiply the answer by 5.04. Like for example on my stepson’s 16 scale E Revo, I’m going to be putting on a 25 tooth pinion and a 45 tooth spur- divide those and you get 1.8 and when you multiply 1.8 by 5.04, you get 9.07, which is listed on the gear chart of his car’s owners manual. Well, no word on it doesn’t say 9.07 because that gear chart doesn’t show anything for a 45 tooth spur/25 tooth pinion but you get the general idea. For my Maxx’s manual, it doesn’t show that in the gear chart but it does show what the gear ratio is between the pinion gear and the spur gear and it does show you how to get that other number when you take that ratio and multiply it by 5.69.

That I couldnt say.

Well, if you were doing a build like this, would you trust that whole aftermarket diff gear assembly the hold up better than the Traxxas ones? Even if the Traxxas ones had the upgraded machined steel ring gear and pinion gear? I mean hey, if a $100 aftermarket differential gear will take whatever I throw at it then to me that’s considered money well spent as opposed to having to rebuild the factory diff all the time being that it probably wasn’t rated for this much power.

I could have sworn that the FDR calculators I've seen online have you plug in diff gears also but I could be wrong. I dont mess with those numbers so I might be misremembering

Pretty much the only useful thing I was able to out of Traxxas support when i was on the chat line with them about what that 5.04 or 5.69 number was, they said it was a combination of the transmission and the differentials. What that means exactly, I don’t know.

 

[Greywolf74]

Well at least one thing about it, changing spurs and pinions on my Revo 3.3 nitro to brushless conversion should be fairly easy so maybe I should just quit overthinking this and just go off of what my infrared temp gun says when I get it running. Although I’ve never been very good at math, I was just trying to figure out a baseline using numbers.

But OK, if that 5.04 number is everything in the drivetrain, are they just essentially taking whatever the gear ratio is in the diffs and adding it to whatever the gear ratio is between the output shafts and the input shaft of the transmission? Is that where that 5.04 number came from?

Yes. Thats right

One thing about it, that 5.04 number is not the same on the different cars.

Its going to be different for every rig.

Well, if you were doing a build like this, would you trust that whole aftermarket diff gear assembly the hold up better than the Traxxas ones? Even if the Traxxas ones had the upgraded machined steel ring gear and pinion gear? I mean hey, if a $100 aftermarket differential gear will take whatever I throw at it then to me that’s considered money well spent as opposed to having to rebuild the factory diff all the time being that it probably wasn’t rated for this much power.

When it comes to aftermarket support I try to makes sure anything aluminum is made from 6061-T6 or 7075 aluminum and I try to make sure any kind of gearing is made from hardened steel.

Pretty much the only useful thing I was able to out of Traxxas support when i was on the chat line with them about what that 5.04 or 5.69 number was, they said it was a combination of the transmission and the differentials. What that means exactly, I don’t know.

the FDR I think is more of a racing spec you would want to know in order to try to figure out maybe max speed or performance on a track or something? I'm not really sure. Again, as a basher I've never found that info helpful at all.

 

[corneileous]

Yes. Thats right

Still good info to have.

It’s going to be different for every rig.

Yep and according to Traxxas, it’s a combination of the front/rear diff ratios and the transmission ratios.

When it comes to aftermarket support I try to makes sure anything aluminum is made from 6061-T6 or 7075 aluminum and I try to make sure any kind of gearing is made from hardened steel.

I tried to ask that from the eBay seller but I think it’s an Asian company so there was a little bit of an issue with the language barrier trying to figure out a little bit more information about it but being what you said that above, I’ll go back to the listing and see if it mentions anything about what the materials were that was used.

the FDR I think is more of a racing spec you would want to know in order to try to figure out maybe max speed or performance on a track or something? I'm not really sure. Again, as a basher I've never found that info helpful at all.

I’m pretty sure you’re right but like I said, I was just more or less trying to use that as a baseline kind of like for example when you’re sighting in a rifle scope and you use a laser bore sighter to get it close. Being that I am converting this to brushless, I highly doubt the gear chart in my original owners manual probably won’t be too much help.

 

[corneileous]

@Greywolf74 @WickedFog

Well guys, after playing around with the old Revo that’s been converted and while using my 14.8V Traxxas 4S Lipo and running the 15 tooth pinion and 38 tooth spur for quite some time, the car for as heavy as it is, has a pretty good amount of speed to it, but it’s still not quite as fast as my fairly stock Maxx. It does have a lot of torque running that spur/pinion combo at a 2.53:1 ratio so now that I have a totally different motor mount on order that should give me a lot more room to play with a wider range of spur/pinion combinations because even during these hot days, my motor with no heat sink or cooling fan only gets up to around maybe 110° to a 115° max so after playing around with the calculator, I’ve figured out that if I leave my 38 tooth spur in place and get a 17 tooth pinion that my gear ratio should drop down to about a 2.23:1 which should hopefully give me a lot more speed but not overwork the motor too much and hopefully reduce some of the torque a little bit so that my center differential, even with 500,000 weight diff oil can actually work how it’s supposed to.

I don’t have a 17 tooth pinion right now so I’d have to order one but I do have a 16 tooth pinion and after doing the math on that, a 16 tooth pinion with the current 38 tooth spur I’m using, should give me a gear ratio of like 2.37:1.