Gruber
HobbyMasters
M.L. Toys
KidsWheels
Gruber
HobbyMasters
M.L. Toys
KidsWheels
HobbyMasters M.L. Toys
Gruber
KidsWheels
Need new motors? Grind a gearbox? Adding teeth to a pinion?
By hizdudeness
#150987
background-
Ok my girls(6 and 3) are rocking out in an at the moment stock Jeep Hurricane. We live on a good bit of property in the mountains. There are no sheer cliff or drop offs, but there are extensive hills- on and off camber. The problems is the hills are not easy for the girls to climb up in a lot of cases.

Current plans-
I just purchased two 12v 12ah batters, one to use now and one as backup, in the very near future I plan to use at 24v with the EastcoastPowerUp ESC to run less voltage with a delayed start. My 6 year old is fearless and is known to be hard on things.

Need help-
I would like to change the motors to less speed at 12v with more torque. I would like more speed for the girls at 24v. Primarily I would like this thing to climb better though. Current GB are the updated 7R variety. Im aware the hurricane is not the best candidate as it is already hard on the GBs. Can anyone recommend motors that would accomplish my goals. I would like to go 775, but I see most everyone is more concerned with top speed. I really want the ability to climb with a maybe a mile or two more top speed.

Sorry for the wall of text. Thanks for reading and any insight you can give.


User avatar
By Hammer-fm
#150995
I'd second the recommendation for 775 motors. Although I think you'll realistically get a much smaller torque increase (than 3x), it will be substantial. Equally important, as the wiring in the motors heats up the maximum torque goes down. The winding resistance is higher so it does not pull as much current when hot -- and the torque is linear with current. A 775 motor has better ability to dissipate heat and should run cooler for the same load.

The improvement can also be limited by the battery's ability to deliver current (or, more precisely, how much the output voltage drops as a function of the current). A typical 12Ah SLA battery's output voltage drops very quickly above 50A, and this limits the amount of current available to the motors (again, reducing torque). In order to minimize this, I would also recommend using both batteries (wired in parallel) all the time. Charge them independently first, then connect + to + on each battery and - to - on each battery, then wire it into the chassis. This will result in each battery seeing roughly half the current, in addition to giving you twice the runtime.
By hizdudeness
#151001
Thanks for the info guys. Do you guys think the GB will hold up to the added torque and the hills? The girls really like the hills. Im definitely going with ESC first as I think it will be better for the GB to get rid of the instant on /instant off harshness. Im just not sure I want to invest in the plastic drivetrain. My kids aren't ready for an atv (at least my wife thinks so, i had a Honda 70 atc at age 4) Im just starting to think throwing money at the plastic gb drivetrain is going to be a bad idea with my future goals. I have found some 16x6x8 tires that I really dig. They are way too heavy to expect a gear box to hold up to with the hills I have on our property. I see a lot of the videos where everyone is spinning out on asphalt and grass and it looks cool, but its counterproductive to what I need where I am. The girls need traction to climb the hills, otherwise they would have to achieve high velocity to get to the top of them..I don't want to push them up either :P

I'm really digging some of the wilder builds I've looked at. My uncle owns a machine shop and my father and I did a lot of car modifications as well. My grandfather assisted me building a go kart/dune buggy with front and rear independent suspension when I was 13. My greatest solo achievement car wise was putting a RB 26 in a 300zx TT. I did all the wiring, exhaust,motor mount and transmission mount fab and ECM programming, but tbh the programming was really off the back of others. The problem is since I moved to the mountains I don't have access to all the great machine shop stuff anymore :( I still have a mig, torches, a die grinder and a dremel. I think I could undertake a moderate project at home. My basement isn't what I am used to having access to though so I kind of feel naked. The collective group has provided lots of information and ideas; I and others greatly appreciate it.

I will start a build thread once I get into it. The girls are having too much fun for me to take the thing off line for any period of time atm.
User avatar
By M.L.Toys
#151002
A Stage IV motor/gearbox kit has no durability issues with hills. The toughest part of offroading is the sudden impacts to the rear tires. But at 12v you should be ok.
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