Has anyone tried using a differential?

Lightweight / Folding / Portable EVs - seats optional
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psychotiller   10 kW

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Re: Has anyone tried using a differential?

Post by psychotiller » Oct 06 2014 2:08pm

Pediglide wrote:I know I'm wasting more of you guys time, but I should have posted this before. Its so simple.

Just think of the one motor on the rear, if you turn and the motor is driving is the rear inside wheel, it doesn't matter how much lean, you will always have traction.

Now if you turn the other way, and the motor is the driving the rear outside wheel, there is a possibility that if you lean too much, you will lift the rear outside wheel and lose traction. <-----That is the same effect of an open differential on the rear truck.

You can counter it, try to avoid it from happening, tighten the hell your trucks, not care about the affect on efficiency or something, but still...its limited compared to when you have the power on the inside rear wheel.

Zboard users complain about this all the time, and they use narrower trucks than mine.
You create outward momentum in a turn right? So that also pushes weight to your outside wheels. Hold a weight on a string...spin around in a circle. Which way does it want to go? just because you lean inside while turning doesn't mean all of your weight disappears from your outside wheels. Which way does your car want to roll over in a turn? Toward the outside of the curve. Placing what?
Answer: All of your weight on your outside wheels.

Zboards could make a lower board, with foot pedals that aren't mounted at either end of the board. That way you could actually have a comfortable/natural stance . Then the board wouldn't have a tendency to want to tip mid turn. Nobody rides a board that way. Problem solved
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rs4race   100 W

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Re: Has anyone tried using a differential?

Post by rs4race » Oct 06 2014 4:23pm

I'm not buying these explanations. I might have to revisit statics. I would suggest that an open differential would allow the board to turn freely, and an posi traction would resist turning.

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psychotiller   10 kW

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Re: Has anyone tried using a differential?

Post by psychotiller » Oct 06 2014 4:44pm

rs4race wrote:I'm not buying these explanations. I might have to revisit statics. I would suggest that an open differential would allow the board to turn freely, and an posi traction would resist turning.
I don't think either way makes a difference. skateboards do not turn like vehicles. With or without differentials. If a wheel loses traction its more likely due to an over-tightened truck or improper set up. Loss of traction isn't even a concern when most people on this forum barely bust 20mph. Definitely seems over analyzed.

This is a cool concept however for motor position.
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Slistack   10 mW

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Re: Has anyone tried using a differential?

Post by Slistack » Oct 06 2014 9:42pm

I tried reading all your posts and this has gotten off topic. I don't think you guys understand how this works. I will try to explain this as best I can. The only reason the differential is good is because you can drive two wheels with one motor. I do think that on turns the differential helps a lot you can hear the differential make a different noise. I have no idea what a open differential is and I don't know why we are talking about it. Also Brushed motors are for plebs. Yes you can run brush motors in parallel no problem, in fact it would be awesome if someone made a controller that did the same thing that subway cars do. Subway cars have several motors they run in parallel until it gets to a certain speed then they run in series so they can have a higher speed. But back to the topic at hand. It doesn't matter whether the powered truck is on the front or the rear you wont lose efficiency. Also if you look at the second prototype the motor when mounted on the board is at a 45 degree angle so that it cant get hurt. Also every longboard has crab steering........ the front truck steers the way you lean and the rear truck does the opposite for a sharper turn. Tightening your trucks doesn't do anything but make it harder to steer. I don't know what you guys are smoking but its no different from a car please try to understand. Also I think that baja board stinks because the differential is like out in the open and will fail, where as mine is totally sealed. I want to keep responding but I feel like this has gotten off topic.

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Re: Has anyone tried using a differential?

Post by psychotiller » Oct 06 2014 10:43pm

I operate heavy equipment for a living and use crab steer. Longboards do not have crab steering. If they did you wouldn't be able to steer much less ride the board. crab steering turns the wheels the same direction allowing a forklift to move diagonally. Closest would be 4 wheel steering if and only if our wheels turned on spindles like 4 wheel steer car.(you would also need C/V axles. It's what I've been saying all along. Our trucks steer from the pivot. Only 2 points of steer on our boards and its under the baseplates. The wheels don't steer anything. I like your set-up. I may buy one from you, but it's definitely being over analyzed.
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Slistack   10 mW

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Re: Has anyone tried using a differential?

Post by Slistack » Oct 06 2014 10:56pm

Thanks man, I dont know whats so complicated about this. It is hard to make and it was difficult to design in such a way that would work. Because on longboards there are forces that want to pull the wheel out and push the wheel in you have to make sure it wont pop out. and make sure no pressure is put on the differential.

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Re: Has anyone tried using a differential?

Post by dirkdiggler » Oct 06 2014 11:11pm

I think the tough thing will be selling this to skaters. They like the trucks they have and is one of the reasons why the altered and emad boards didn't do so well. One of their reps was on here for a while and mentioned that most customers were surfers or snowboarders. With the homebuilt boards they get to use a setup they are accustomed to riding. Its easier for them to swallow that way. The other issue is you will have to be comparable in cost to what a belt drive is. Lagrange has a great truck setup, but the cost isn't worthwhile for most of us. I know you said the diff is only $20, but all that machining is expensive.

My bro recommended I do a diff - probably mentioned that earlier - but I'm not a machinist and it takes a bunch of effort to get something like that made. I would suggest you still cut down some size on your diff, if you can. Even though it probably isn't much heavier, it will still change the ride of the board. Can you the axle down to 20 or 30mm? If the pic has 83mm wheels - that looks to be 50-60mm, which is pretty thick and they will hit road debris. My trucks get beat up at normal height. The nice thing is you don't have to worry about baseplates if you make it fit standard trucks.

I've thought a few times of just using a pinion gear with a spur gear/slipper clutch, but I've had enough issues with RC cars stripping gears. Eboards have a much lower rpm, which likely would save some damage. You are right about just replacing the diff instead of trying to repair it. Spent way too many hours tearing into those to replace a $2 part anyway.

Have you thought of using like a Baja 5b diff with a clutch and pinion gear? Those diffs hold up to some 100cc engines. More than comparable to what we use. Plus they are still only around $25.

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Re: Has anyone tried using a differential?

Post by Slistack » Oct 06 2014 11:33pm

You are right the outside diameter of the housing where it is rounded is 1.8 inches, it can be cut down to 1.366in with out any problems I just left it thick cause it looks nicer rather than skimpy. I also think this is a premium product and should cost more than a belt drive system one because it will last as long as the batteries and it is simply better made. I mean the most important thing about trucks are the bushings. I can make it wider narrower whatever but it call comes down to the bushings and you can just throw in any kind you like. the clutch is also unessisary for an electric motor. I would not like to use a bigger diff because it makes everything 20% bigger heavier and clunky I want to keep it light and simple so it can be used on a small board. I wouldnt mind making a boss ass one if you wanted one but I am not really interested in a heavy beast.

rs4race   100 W

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Re: Has anyone tried using a differential?

Post by rs4race » Oct 07 2014 8:42am

i still wanna see some of this action on a board. I wouldnt mind doing 2 motor 4wd on my mountainboard.

Slistack   10 mW

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Re: Has anyone tried using a differential?

Post by Slistack » Oct 07 2014 8:08pm

I think 4wd would be cool for winter purposes.

Ender wiggin   1 mW

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Re: Has anyone tried using a differential?

Post by Ender wiggin » Jan 16 2016 8:55am

So is this thred dead? I would love to try and put some dif on my mountain board.

Slistack   10 mW

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Re: Has anyone tried using a differential?

Post by Slistack » Feb 22 2016 12:24pm

I have had trouble finding big enough differentials for mountain board use. I am sure that they are out there. I just don't need it for that use. Sorry. If you have any questions let me know.

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Re: Has anyone tried using a differential?

Post by iamthekwan » Aug 21 2018 2:23am

It's been 2.5 years since the last post... wonder if anyone has any news about the differential? I found one promising guy https://www.instagram.com/p/BPcu3YWh1P2/ but it feels like the project is dead, which is a shame.

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