Twin motor multi gear. Good idea, or a joke?

[Easy-pd]

Just an idea from a layman, halfway through his first build. It may already be in use and I have not read about it. It may be a poor idea, it may be a good idea, but I thought I'd share it, as my technical knowledge is not up to building it if it has any merit.

I see a lot of twin motor builds. It just occurred to me that if you had a twin motor set up, but each motor worked independently and one at a time on different gearing, it could work more efficiently. I am not an engineer and this is just a thought I thought I could share to the more experienced crowd.

What if you had one motor with gearing for super fast acceleration up to, say, 10 or 15 mph that stopped when it reached peak rpm for the second motor, with gearing set for cruising/high speed to kick in?

It could be like having two gears, potentially offering higher speeds and acceleration.

Don't blast me, just an idea.

Thoughts?

 

[torqueboards]

You can't control them independently unless you had perhaps a custom ESC and a controller which would trigger each motor separately.

You also would need to lathe the truck and attach a bearing to spin around the axle to ease the resistance from belt.

But then you would also be limited by the belt and gearing ratio of the second motor since no matter what you would be pulling/pushing that gearing ratio.

If you have one that is higher and second one lower it's only as good as the other.

So in other words, it wouldn't be doable unless you did something completely different and didn't use belts.

With all that said a dual motor with a specific gearing and 12S voltage. I think it's more then adequate for anything really. Doubt we need to develop a crazy gadget for all that.

I'm able to get to 10-15mph faster than I'd want and go up hills 30-35% higher.. If anything, I'd want maybe 14S or 16S with ridiculous torque for powering up hills but probably a bit overkill.

I'd assume if people want to reach 60mph.. that's another story which I'll watch but won't partake

 

[psychotiller]

I agree with Torque. I have 2 boards right now that push 50mph using a single motor set up. I as well am just about over partaking in going that fast.

 

[Hummina Shadeeba]

Just an idea from a layman, halfway through his first build. It may already be in use and I have not read about it. It may be a poor idea, it may be a good idea, but I thought I'd share it, as my technical knowledge is not up to building it if it has any merit.

I see a lot of twin motor builds. It just occurred to me that if you had a twin motor set up, but each motor worked independently and one at a time on different gearing, it could work more efficiently. I am not an engineer and this is just a thought I thought I could share to the more experienced crowd.

What if you had one motor with gearing for super fast acceleration up to, say, 10 or 15 mph that stopped when it reached peak rpm for the second motor, with gearing set for cruising/high speed to kick in?

It could be like having two gears, potentially offering higher speeds and acceleration.

Don't blast me, just an idea.

Thoughts?

having two esc, two motors, but with different gearing,.. I think your low geared motor, (what "low geared" means probably is vague and not universal, but the one with a big cog on the wheel and small on the motor) will ultimately slow you when you try to go beyond it's kv x volts number. In fact I bet it would totally fight against you when you tried to go beyond it's max rpm decided by that number.
but no joke and a great question

 

[Easy-pd]

Ha ha, another one of my ideas to make my millions bites the dust. Explains why it's never been done before. Thanks for the comprehensive answers. I would've been left wondering otherwise...

 

[LEVer]

You could actually do it, you just need to use freewheeling clutches. The problem there is, you lose regenerative braking. You could use mechanical brakes, but from someone who has built boards with them, it's more of an added complexity. Two motors are adequate enough for braking.

 

[Vanarian]

You could actually do it, you just need to use freewheeling clutches. The problem there is, you lose regenerative braking. You could use mechanical brakes, but from someone who has built boards with them, it's more of an added complexity. Two motors are adequate enough for braking.

I got beaten to the reply :lol: Actually I'm pretty sure that with motorised clutches you could keep the regen braking but for the price, weight, complexity and maybe weak links added it is (for a board) too much of a hassle and not beneficial enough to think about.

If you want millions make a "Back to the future" hoverboard, aren't we in 2015?

 

[onloop]

I have thought about this before many times...It is possible. But i doubt it is worth it and I will explain why at the end.

The secret is to make sure each drive train is geared / designed to reach the same top speed.

There are 4 variables.
1. Motor kv.
2. Motor pulley teeth qty.
3. Wheel pulley teeth qty.
4. Voltage to each motor.

So generally to start moving a load and to climb hills you want max torque. So you setup one side to have more torque in low rpm. Higher reduction ratio.

The otherside you want to have more torque at higher rpm. Near your top speed. Lower ratio.

As you start slowing down, say when you start a hill clmib, the one that is geared for more torque at lower rpm is now doing most of the work. It's carrying the load.

The question is how do you determine where the peak torque of a particular drive train is at? You could just guess! Or You need a dyno. Or at least a way to measure watts under load. Then you need several different drive train configs and start testing until you find two different ones that have the same top speed but with different torque curves.... so i think it's pointless.

The reason you don't need to do this asymmetrical setup is because you can simply build a symetrical dual drive train with ample torque throughout the entire range of rpm... so in real world terms, a drive train that at the bare minimum has enough torque to get the desired load up the desired incline.. then if top speed is too slow just increase voltage and the torque stays the same but you go faster.

 

[magiced]

I work for a company that has made some pretty powerful electric vehicles, and we've done this extremely successfully, so it's a working, proven idea! One version used two motors, with different pulley sizes into a belt transmission, and on the other the front and rear axles had different gearing.
However, the motors we use have encoders and the inverters we use are a bit smarter than your standard RC ESC and let the the low geared motor freewheel when the speed gets higher and the higher geared motor takes over. It provides you with full torque for a greater proportion of the rev range. it felt goood.

Once i've built my board I was considering trying this concept out using cheaper parts, but i need to get get one motor working first!

But if you can get a simpler drive train working with enough power to scare you, (at a lower cost) why not do that?

 

[Vanarian]

I will add that You drastically reduce constraints with hub motors and only have Voltage and Kv left as variables ; again it becomes useless to use variable Kv because even a low Kv 63mm (standard size for boards) wounded for say 80Kv will give you tremendous acceleration and since hub motor is 1:1 ratio, record breaking top speeds (read : unachievable in real urban conditions)