M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
Need new motors? Grind a gearbox? Adding teeth to a pinion?
First up - A huge thank you to everyone who has written up their experience and learning from modding their BPRO over the last decade! In 6 months of picking up this addiction, I've gone from newbie ignoramus to semi-competent modder, thanks to you all!

I'd really appreciate your advice on how to wire up my 4WD jeep. I've read lots of views here about which way to go:
    1) On each side, wire front and back motors in series, and then the sides in parallel*
    2) Wire diagonally opposite motors in series, and then each diagonal pair in parallel*
    3) Or just run all 4 in parallel
* And probably vice-versa too! :lol:

I got the basic 4WD up and running quite easily. But it's time to upgrade the stock motors and what remains of the stock wiring, so I'm going to do it properly. But I've realised that I don't understand the pro's and con's of each configuration option. I'd really appreciate it if someone could explain that to me, so I can make the right choice for my situation!

Thanks folks.

Some background info, in case that helps:
    - Original vehicle: A fairly standard Hummer Jeep, RWD, 2x 35W 10,000rpm motors. Non-PW branded.
    - I have added 2 similar motors and gearboxes (the kind you get off eBay - with a teardrop-like shape similar the the PW #3) to the front axles.
    - I have the luxury of a decent speed controller from the guys at 4QD - 24V 100A. Currently dialed down to give 18V max to the motors.
    - Motors are currently wired all in parallel.

Just to get it all working and to prove the concept, I just soldered diagonally opposite motors together in parallel and ran the gear shifter in the 'slow' series position. My ESC is 24V, so each motor saw roughly 12V each. Once that worked, hooked them all up in parallel (option 3 above) and dialed down the max throttle position on the ESC, to give 18V to each motor at full throttle.

My current thinking is that I should keep the motors all in parallel, because as soon as I put any 2 motors in series I'll be limited to 12V maximum at the motor. And I'd like the flexibility to go to 18V at the motor (I have a couple of 12V Mabuchi 550s in my Dune Racer, over-volted to 18V, which goes quite nicely :D; and a couple of pairs of 18V Mabuchi 775s waiting in the spares box for me to make up some spacers :D )
Despite all my sinister plans :twisted: ... I've only succeeded in completing one 4wd project. :(

I wired the motor all in parallel and it created an extreme torque-steer problem. On an empty muddy field it's just fine, but try to throw any sort of technical navigation into the mix and it becomes a handful. Everytime my kids try to get on the gas the front axle snaps straight forward, typically into whatever obstacle they are trying to avoid...

It's become un-fun to them so they don't ever drive it anymore. Long story short, ideal configuration would be 36v ESC, motors linked front to back in parallel and driver side / passenger side in series. This way, at least one side of the vehicle will always have power, you won't have two tires spinning if you get crossed up in a little ditch. Since you aren't locked left-to-right, the steering is not quite as bad though you could still have some push on the front end.

My $.02
Only one? Think handle bars would help, as in a quad, vs a steering wheel?

Do you by chance recall how you secured the gearbox to the axle? I've seen zip ties, but can't imagine how long that'll last.... the old #3 had that nice flat, or the slit between the flats, but on the brute force I'm going to try it on, it's #7's.
Handlebars would probably help some. I used old #3 boxes with 775 series motors in them. Best I can remember I used tie straps to hold them in place. Come to think of it... in my signature there is a project link and I'm sure I have photos in there of it. It was a white jeep
Thanks for that info of wiring configs. It'll help me get my head around what wiring in parallel vs wiring in series does to the power delivery.
I don't have a 36V ESC to hand at the moment - well not a decent quality one, like my 4QD one. So I'll do the upgrade to the 775 motors first, then run through some wiring config options 24V (12V per motor) to test the theory.

I don't seem to get the torque steer problem that you encountered. I suspect that might be to do with:
- having only the weak stock motors in there for now
- running the front wheels faster than the rears by about 10%
- or the rather 'interesting' way I mounted the front gearboxes to the axle.

I'll do the 775 upgrade first, and see what happens! :)

Thanks again
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