sschering

iTrader: (4)

My wife asked me to fix my son's old New Bright H3 hummer..
Her thinking was to replace the radio and dead battery.

I had another plan and it just arrived today



Mix those two with my old Dewalt 12v drill and a Traxxas EXV-2 ESC and you get what I'm thinking of doing..

The Hummer has a longer wheelbase so I will swap in a Rival frame to add another inch to the wheelbase.

Phase 1 is getting the drivetrain put together.. I need to make a mount or the Dewalt 12v motor.

Overdriven

iTrader: (18)

I like the way you're "fixing" (lol) your son's truck! I found a 1/6 New Bright truck and used the body on my old emaxx. Had to extend the chassis about 4" if I remember. It looked really cool but the body broke into multiple pieces the first time I rolled it. But that was at brushless speeds too.

Is the mounting for the Rival trans the same as the MGT or do you have to go with the Rival trans in the Rival chassis?

sschering

iTrader: (4)

Honestly I'd prefer to use the Rival trans but between that and the slipper I'd be spending another $70-100. At that point I may as well do a center diff mod.

The 2 chassis are close but not quite the same..

I think I'd have to open the top of the Rival up a bit and drill a few more mount holes to mount the MGT trans.

Rival

MGT

I'm also still entertaining the idea of making my own chassis from Aluminum and CF plate.

The Hummer wheelbase is 16".. Rival is 15.5 but would look ok I think but 16" would be better.

I bet I could build my own chassis for around $15 in aluminum and screws plus the CF I already have in the shop.

I need to strip the truck down and take some measurements before I get to involved in that.

I'll probably do 4S power because I have a few 4s 5k packs laying around doing nothing.

Random facts so I don't forget them..

Chassis walls at the top are 0.263" and step to 0.70" at the skirt.
chassis side wall is 1" tall (bottom of chassis to bottom of ears (ok 0.990 but whats 0.01" between friends)
chassis top and bottom plate is 0.85" thick.
Main channel of the chassis is 2.367 OD and 3.95" at the ears.

MGT front and rear CVD is 2.75"
Rival front CVD is 6"

Overdriven

iTrader: (18)

1/2" difference in wheelbase isn't going to look bad, divided up each wheel will be 1/4" off. Hardly noticeable in my opinion and not worth the trouble of going custom. My Emaxx I had to add 3-4" but that chassis was easy. With 2 sets of chassis braces I was able to make one long set by cutting off the ends and using the center skid holes to attach aluminum angle. The left over aluminum angle spanned the distance between the chassis and the rear bulkhead. I guess you could do something similar with the MGT chassis instead of buying a Rival chassis or making your own. I'm not that familiar with how the MGT/Rival rear bulkheads attach but maybe cutting the rear section of the chassis off and using plate or angle to extend it is possible.

For the new rear driveshaft I just cut a spare dog bone in half, sleeved it with steel brake line and welded it together when I had it straight.

Total cost was about $20 for the chassis braces and aluminum angle at Home Depot. I had the brake line and extra dog bone. I love doing and seeing projects like these. I actually have another large scale body sitting on the shelf waiting for a chassis, just need another LST roller...

Oh what the hell here's a pic of my old Emaxx. Maybe it'll inspire something.

[IMG][/IMG]

ramensidevd

That's very nice little vehicle car.

sschering

iTrader: (4)

Well as much as I like making my own stuff with carbon I couldn't beat $17 shipped on a Rival chassis. It's on the way..

Now to focus on the drive train.

I pried the motor from the dead drill's carcass and found out it's a fatty..

It won't come close to meshing with the stock 52t spur. The trans bevel drive is in the way.

My options are..

1. Try a T-max 72t 32p main gear with a BIG pinion to bridge the gap.

2. Build a motor mount with a bearing supported shaft extension to move the motor back clear of the bevel drive. I have this mostly planned out in my head.. I think it'll work. Having a lathe doesn't hurt when it comes to making round stuff.

3. Drop $30-40 on a RC8 center diff and make mounts.. now I'd have to get new dog bones too.

4. XL belt drive? could be fun.. way off the normal path here.

Overdriven

iTrader: (18)

MGT 52t spur = 54mm diameter, TMaxx 72t spur = 58.75mm. Not much of an improvement in clearance but it is something. Have a look at the ERevo 68t mod1 spur which is 70mm diameter. It's not a bolt on like the TMaxx gear but with the slipper locked it'll work and give you more clearance.

Your bearing supported motor shaft extension is an interesting idea. Biggest complication I see is lining the motor up square with the extension and keeping it there. The extension itself and the bearing supports are fairly easy to make. The shaft coupler and pinion along with some sleeping for spacers (if necessary) would keep the shaft from moving around in the bearings.

Belt drive could be interesting. Where would you get the belts though? That and I wonder if the end of the trans and motor shafts should be supported so belt tension doesn't kill the inner bearings.

Sorry if I'm a bit much, I love discussing custom builds. The pros and cons of different solutions, etc. For $17 shipped the Roval chassis is the way I'd go too, nice score.

sschering

iTrader: (4)

Overdriven: I welcome any input anyone has. especially those who have done these kinds of mods before.

As for timing belts they are easy to find.. McMasterCarr has a good selection. Servo City is good. Even Amazon has a few plus pinions and spurs.
http://www.mcmaster.com/#timing-belt-pulleys/=w2vpb3
Since they are toothed belts they don't need a lit of tension. they work well in touring cars so I figured a bigger stronger version may work well here too.

After playing around with the transmission last night I've decided to get rid of it.
I'd have to keep a reverse servo and brake servo (one way gives no motor braking) plus the spur is melted in the center.

I did a bit of Dollar Hobbyz research and ordered an Ofna 1/8 Ultra LX2e center diff.. $23 shipped with a 50t mod1 spur, 14t pinion, support bearings and all.

There are a couple good reasons I picked it other than it being a nice deal.
It uses standard 607 7x19x6 support bearings.. I already own tooling to make flat bottom 3/4" holes so it's easy to mill the bearing pockets.. 19mm is only .002" smaller.. a perfect match.

The out drives cups have 5mm stub shafts.. It should be a simple task to make a new set of stub shafts from 5mm drill rod that will let me bolt on the MTA drive shafts rather than buy new dog bones.

I like this plan because I don't have to buy tooling other than a small metric bit to drill the pin bore in the stub shafts.

I have a Rival front shaft on the bench already.. The plan is to mount the center diff to use the stock MGT rear shaft and cut the rival front shaft to fit.

It'll be fun to see how this plays out.. This CD is more compact than the rival trans so it'll be interesting to see how it all fits.

Next stop.. the metal store for 3/8 aluminum bar stock.

Overdriven

iTrader: (18)

I like home brew stuff in general. I do what I can with a Dremel, drill press, hand tools and welder. With rc that means my own electric conversions (mounts, battery trays), chassis extensions, etc.

I looked it up once and the MGT trans is fairly easy to lock into 2nd gear so you can use esc/motor brakes instead of mechanical. But you'd still need a forward only kit and deal with the spur issue.

Wow only $23 for the whole LX2e center diff unit? I spent that on just the mount last time I converted an old LX buggy. Definitely cheap enough to warrant not messing with the trans. If you can I'd put your diff output extension on the spur gear side. The metal cap on the spur side would be able to take any side loading (shouldn't be much if any as the extension isn't that long) better than the plastic diff cup. Well standard practice is to sink the cd down in the chassis and mount the motor over it. Makes for a nicer layout as there's space on either side for the battery packs.

sschering

iTrader: (4)

It's just the Diff for $23 shipped
http://www.dollarhobbyz.com/ofna/ult...ferential.html

Funny thing is the LX2e diff/motor mount costs more $28
http://www.dollarhobbyz.com/ofna/ult...iff-mount.html


The mount is not really worth it when I'd have to modify things a bit to make it work.

My tools on hand are a lathe, drill press, band saw, sanders, files and a router table for light work..
Yes you can route aluminum if you take shallow passes and run at low speed.

I have a friend with a Bridgeport mill if I need to get serious about hogging out metal.

I may make prototypes out of HDPE. It's easy to machine and would survive a test run or two.

sschering

iTrader: (4)

I picked up a 3x24 3/8 aluminum flat bar from the off cut bin. $5. not bad..

chassis and diff are here.. pinion is MIA so I gota deal with that..

Hopefully tomorrow I can pull the front and rear diffs and see how the drive lines will work out.

I think I may need a 2nd rival front shaft. Edit.. No it's almost perfect with the rival front and MGT rear shaft.

Trying to figure out the best option.

1. make new output shafts for the center diff.

2. bore the AE CV aluminum ends to 8mm and run em backwards with the CV end on the front & rear diff and dog bone to the center diff.
This is my favorite idea so far but I may try making my own CV ends for fun.

3. get new dogbones.

sschering

iTrader: (4)

Looks like I'll be taking option 4..

Make my own drive cups for the CV shafts.

My Daughter wants to help run the lathe so we will be trying to make new drive cups that fit the input shafts on the front and rear diffs. That way I can use the dog bone ends on the center diff. Worst case I waste $2 in aluminum bar stock and some time... No big deal.

sschering

iTrader: (4)

Well my proof of concept worked out great on an alternate method.

I took the old MGT blue CVA output cup and bored it out to 8mm on the lathe.
That effectively removed the little flange on the end in the process.

Anyway the thing bolted right onto the rear diff with no other mods.


I'll still try making my own cups just because it's fun but it's nice to know a simple solution is available.

sschering

iTrader: (4)

Progress!

Here we are with the diff side of the cup done.. fits nice. I need to figure out what thread the pin has so I can tap the cup for it.



A few more hours at the lathe and we get this.
Not bad for a 60+ year old manual lathe.



Fit to the diff.



The spur is a biggie.. I'll need to notch the chassis top plate to get it to sit down where I need it.. I think the bearings centered on the top plate will be about the perfect height.



We will get the front cup done tomorrow then move on to the diff mounts.

sschering

iTrader: (4)

Hmm the stock front diff dog bone cup is giving me trouble.

The pin must have locktite on it.. That thing won't move.. I may have to pull the pinion out and try some heat to get it free.