Starting from scratch - MT conversion
 

Hey all -

Been gathering info for a while about doing a BL MT conversion, and I decided on either a MGT, or an E-Revo.

I'm really keen on the MGT, I had quite a few nitro flavors over the years, bashers only though, and I really like the truck. And, I have a ton of spare parts sitting around for it, which is a bonus.

I like the E-Revo as well in theory, the videos look cool, nad there seems to be a lot of support for conversions.

I'm leaning towards the MGT though, but honestly wouldn't mind either.

The issue with the MGT is the tranny. I saw a few posts online where people have rigged up a center diff, which I would probably prefer over a tranny, just to keep it simple and also maintain reverse without extra parts. I emailed Mike regarding the issue and haven't heard back (only been about a day though), but I think he'd be the guy to help me rig something if need be. I just don't know if I'd be able to get that "holy shnikies" wow factor flip on it's lid power since it is such a big truck. I'm not current on the actual power output of some of the BL motors, but I can figure that out after I have the hard part done (tranny issue).

I really don't know much about the Revo, but have seen a lot of threads with conversions. Do people start with the new 3.3 chassis, and go from there, or do they find the 2.5's and use those for whatever reason? Is there a drop-in motor mount for either chassis options?

Just parallel processing some ideas while I wait to hear back from Mike. I'm ready to get something going though. I sold off all of my cars/trucks about a year ago, just to take a break from the hobby, but you all know how these things are, they call your name in your sleep. I have to start from almost nothing, so I can go with either option above. I'd prefer the MGT if I can get the power I am craving, but I just don't have a machine shop handy to figure out solutions quickly/neatly.

Thanks in advance,

10k

Welcome to the forums!

I have no experience with the MGT, but the Revo is a fun truck to convert. The only challenge really is figuring out where to put stuff since the shocks eat up a lot of the space in the middle. The chassis is totally up to you. Some like the longer chassis and it offers more room for equipment and may tend to wheelie less. For me, the 2.5 chassis is fine.

Either way, you'll like the results I think!

Actually, sitting here thinking about this a bit more -

Could I just use the existing tranny, with the 2-speed, and a Forward Only Kit like I would normally do with it in nitro flavor?

I think the tranny is strong enough to handle anything thrown at it, and would let me keep using stock parts. I would just need to find a way to mount up the motor in a good place, with the spur gear on the side like it is.

Could I gear it appropriately to get the torque and power I'm craving (pinion options)?

This would require manual braking, which isn't a huge deal and actually I think I'd rather stress that little disc brake than my expensive ESC, especially with a heavy truck like that.

Hi 10kman - Welcome to the forum. I was very big into the MGT until recently getting into the LST2. Here was my attempt at an MGT converson. I tried to make my own mount and had terrible flexing issues with it. I finally had Mike mill me some diff mounts based on some drawings from Coolhandcountry had submitted to him a while back. She runs great now but I haven't run it much recently since switching over to the LST2.

Good luck with your build and please keep us posted on how it goes.

Thanks...
 

Hey Rice -

I remember seeing your post over there, I'm still toying with the idea of using the actual tranny in the truck so I have a 2-speed BL MGT. I think you'd have more room for a sturdy motor mount too, because you can put it where the nitro engine usually is on the chassis.

I think since the motor would be mounted with the shaft to the right, you'd have to run the motor in reverse for forward motion, which can probably be done with the radio settings.

I'd have to figure out the motor mounting, but I think it'd be "easier" doing it that way, rather than trying to do a center diff with non-mgt driveshafts.

This thing is consuming my entire brain, and I'm supposed to be working!

I did an MGT conversion. I didn't want to over complicate things, so I used all stock parts plus the forward only kit. I just opened up the tranny and pinned the oneway, to the second gear actuator (is that what it's called). Mine is first gear only because I wanted something to get crazy with. I got the smallest spur gear and have a 16 or 18T pinion with a 7XL. This thing is stupid. My son actually drives it up tree trunks and does back flips with it. He's also flopped it flat on it back and it bounces back onto its feet. I can't say enough about this truck as a play toy. If you want more speed, just go with the second gear and gear appropriately. Just make sure that you do set the slipper. If you get no slip, it will break the second gear shaft inside the tranny. We've done it half a dozen times. Good thing the shafts are cheap and easy to change. I used 1/4" angle to make a motor mount. The whole conversion took me about 5 hours to do.

http://i154.photobucket.com/albums/s...r/DSCF0093.jpg

http://i154.photobucket.com/albums/s...r/DSCF0094.jpg

http://i154.photobucket.com/albums/s...r/DSCF0095.jpg

BTW, there are only 6 friction pins in the slipper, using only half the available holes. Get another set and use all 12 holes.

The trouble with most two speed auto-shifting transmissions (which I'm assuming the MGT uses) is that there is a OWB on the first gear. This means that you won't be able to use motor braking and motor reverse. So, you'll have to use disc brakes with a servo, but I don't know about reverse. Not sure if this applies to the MGT, but it's something to think about...

I should have explained the purpose of pinning the oneway to the second gear actuator. I actually put the whole tranny shaft on a drill press and drilled three holes through the actuator into the one way and tapped the holes 3mm and put screws through the holes. I then filled in around the holes with jb weld. It is all very solid and after over a month of torture, it hasn't moved. All of this sevred to lock the shaft and all gears on it, so I now have motor breaking and reverse without the reverse plumbing. I'll have to try to pull the shaft and snap a pic. I'm just not wild about pulling everything apart just to take a pic. The shaft and gears are still accessible and replaceable, should the need arise.

Nice truck up there, that's what I was picturing in my head. Isn't the low-gear really low for your setup, or is it still plenty fast for your needs?

I really would like to have a 2-speed, if I can make it last anyway. I bet having 14+ cells banging into 2nd gear isn't going to be pretty.

Don't worry about a pic, I have had many MGT trannies apart and know what you mean. Plus pulling it out isn't worth it just for a picture, they have schematics on their site that work as well.

You can simple use a Y cable on the brake servo/controller to use the mechanical brakes.

For some advice on the conversion you are planning to do;

If it's your first brushless vehicle, i would convert what you've got'. that way you've got a perfect reference to decide what you want, nitro or electric.

Since you have got lots of spares for the MGT, i would convert that MGT before getting a revo. You can learn from your conversion, and build it back to nitro if you do not like it. (i don't think that will happen though) and there is always room to get a revo, you know..

It's not my first brushless vehicle ever, but right now I have nothing to put towards the project other than a bunch of spares for the MGT.

I had a Lehner 5300 in a TC3 for top speed runs with a Schulze controller way back, and also had one of the first Novak systems in my T3 truck. Way nicer than brushes, and they sound cooler too when they wind up.

I'd like the disk brake to be my stopper, so the Y-harness would be ideal. I disable reverse on the ESC, and the radio will take care of moving the servo anyway right, to actuate the brake?

Yes, that's about it. Some servo's can be programmed no to follow the throttle to WOT, but the same stuff as used on nitro's can be used on the electric.

Sorry, i meant; brushless MT's. A brushless 1/10th is something different than an MT. more power.. :)

About the brake: yes. Or, if you have an AUX channel and channel mixing on your radio, you could use that instead of the Y harness.

If I had it to do over again, I'd go the route that you guys are talking about just to try it, with the mechanical brakes. I did what I did because the MGT that I got didn't have all of the parts to it. It was a stripped roller and I was really not familiar with the MGT as a whole. I used what I had. The way that I did it, keeps things really simple though. Fewer things to break or go wrong and when they do, it's really easy to fix.

My MGT is plenty fast for running on big tires. It isn't stable enough for any more speed. As it is, it's almost fast enough to run on a track. I built it for my 8 year old and I really don't want him having anything that weighs about 13lbs going very fast. LOL

This was what I was thinking and went that route on my LST2. I had to upgrade my radio though to one that was capable of the third channel miixing. Not an inexpensive otpion if your radio doesn't already have that feature.

Oh yeah, an 8 year old with a 13 pound truck is more than enough right there, throw in some speed and you have yourself some damage waiting to happen.

How many volts did you run on your 7xl setup?

That's true, but nice if you have it. If not, the Y adaptor works well too - you just don't have all the seperate EPA/range/etc adjustments you would with the channel mixing.

Personally, I like locking the tranny into one gear and using the motor as the brake and reverse. A lot of times, you can remove components out of the tranny making it simpler and lighter (less rotating mass). Plus, less overall weight and complexity since there are no metals discs, servo, linkage. It is a little harder on the ESC though...

Yeah, the lighter weight is a nice feature of not having all of those parts, plus, like you said, it is simpler and less stuff can go wrong.

I'm wondering if locking it into 2nd gear would be too high for BL power? I'm thinking it would be fine with a big powerplant in there. There's so much room on the chassis on the MGT that you can run plenty of cells to suit your needs.

But, the ESC strain worries me as they are expensive. What ESC's can handle that kind of strain without causing any issues in the near and long term? Assume 14-16 cell voltage ranges for this project, so what is that, 4s/5s LiPo?

What's the weight, final gear ratio, and tire size of the vehicle? If heavy, geared kinda high, and using larger tires, it does place a larger strain on the ESC. I think an ESC with a solid 120A+ rating should be OK...

Depends on your motor and batteries really. I went with stock second speed gearing on my LST2 and was still pulling wheelies. I recently went up three more pinion teeth on my LST2 and the MM didn't even blink.


Roughly figure 1.2 V/cell NiMH vs 3.7V/ cell Lipo. Set up with BEC the MM will handle 4S. I've put 5S on my BK 9920 in the MGT no problem. Did have to run a fan on it though

Drive ratios according to web searching yield this -

Transmission ratio: 8.132:1 (first) 5.624:1(second)
Final drive ratio: 28.22:1 (first) 19.51:1(second)

So, assume 2nd gear locked, and 13 pounds is probably reasonable for a weight guess. Tires I don't run super big ones, maybe 5" max.

~19:1 is a fairly typical final ratio for a MT with those sized tires (which I think are 5.65" IIRC for standard MT tires). Shouldn't be bad at all even locked into second gear. Of course, I'm assuming your motor will be the typical XL size motor found in the RCM store. If it is an L size, the two speed might be better off.

:Off topic: If you know the gear tooth counts of the diff ring/pinion, and the tooth counts of the tranny gears, I'd appreciate those numbers to I can add them to the speed calculator presets.

I found this -

http://alumniblinds.com/MGT/MGTINFO.htm

I'm looking for actual numbers though, I don't think this stuff is in the manual to that level of detail.

LOL, I've actually counted teeth from manual drawing before. If the manuals are done right in PDF form (using true vector drawings), you can resize them as big as needed with perfect resolution for counting. Also, sometimes you can get tooth counts from the parts list. If all else fails, I just go to the LHS and count the teeth in the package. :)

I'm running the MGT on 4S lipo. Nothing off the wall. As for the strain on the esc due to braking, I don't think it's a problem. I remember seeing my MGT running when it was in nitro form and owned by someone else and the braking wasn't "all that." When I converted to electric, I kept dialing down the brakes until the truck would brake without flipping over. Apparently, the motor braking was a lot better than the stock setup. I'm only running 30% on the brakes and it stops the truck pretty quickly without locking up the tires causing the truck to nose dive and flip.

10Kman, if you are looking for speed, perhaps keeping the two speed is the way to go, but you said that you are familiar with the MGT. As you know, the second gear setup doesn't look like it could take much without modification. All that's kicking it into second gear is that little arm that pops out on the rear disk of the second gear shaft and all that's holding that in place is a little set screw. I don't think it will hold up.

I suppose that you could lock first gear and use a low kv motor with lots of cells and use a large pinion to get it moving faster. I do have to say again though, going fast isn't the strong suit of the MGT with the large tires. This thing as I have it setup borders on having rock crawler status and is a hell of a basher in confined areas. It's the most fun RC vehicle that I have, although it is the slowest. The lack of speed also means much fewer broken parts. In over a month of thrashing, I've only had to replace one lower arm.

Update on the project to make it "officially started" -

Ordered up a brand new MGT. I was thinking about trying to get a used one and just giving it a going over, but then I realized that I am scrapping a lot of parts off of a new one, and will rekindle some money that way.

So, got a new MGT RTR, Forward Only Conversion, and some diff shims coming right now. Once I get it, I will tear it down anyway to do the shim/tranny conversion, and give it a once over with some loctite where necessary, shrink wrap the CVD's to keep the screws in place on the cups, and get it bulletproof.

I'm going to take the nitro parts right off and sell them as a kit, and probably the radio gear as I already have 2 JRXS3's sitting around with RS300 synthesized receivers as well, and a 958Z servo for steering. That will give me back plenty to get the Feigao 7XL motor that I am going to use, and probably enough for some aluminum from Lowe's and some small tools to hopefully get it cut how I need to mount up that motor. I wish there was a mount out there to do it already, it's simple enough really to just bolt to the chassis.

Then I'll just have to figure out which ESC I am going to use. I'm thinking I can save some cash if I use the mechanical brakes rather than the ESC's brakes, so I won't need as high of an AMP rating.

Any thoughts on ESC's for the application? I'm assuming I'll need a BEC as well, which I do not have experience with, I have always used a receiver pack but do not want to have another pack on the truck.

I also need battery packs and probably a new charger if I switch to LiPo, if not my MRC 969 will do fine up to 8-cell packs, but then I need a series harness.

Once I get by the mounting of the motor, I will be in a better situation.