ES DIY Motor Challenge

[Farfle]

Maybe we could get one kudo just for entering??????

At least one kudo for entering a legit torque number, that takes a bit of dedication to find.

[Miles]

Steady on.... We don't want to devalue the kudo...

[Farfle]

Steady on.... We don't want to devalue the kudo...

Lol, no false kudo inflation.

[pkirkll]

[Miles]

Edited the first post to add the new rules.
http://www.endless-sphere.com/forums/vi ... 30&t=14484

[Lebowski]

somehow to me the rules don't make sense (sorry )

with the specific torque etc, what it boils down to is

Torque should be larger than 0.2 * kg ^2 + 3 * kg

The weight (kg) squared means... well... lets say we have a motor with a certain weight. Taking two of
these and putting them on the same axle means the motor weight doubles and the torque doubles. But,
because of the square term the torque should more than double to be conform the challenge.

My feeling is that if one motor is conform the challenge, two of these motors combined should also
be conform the challenge...?

[Miles]

Let's try with the example I gave.

1.2 kg motor needs to output 3.9 Nm

2.4 kg motor needs to achieve 2.4 * 0.2 + 3 = 3.48 Nm/kg

This requires 3.48 * 2.4 = 8.35 Nm

What's wrong with that?

[Lebowski]

Let's try with the example I gave.

1.2 kg motor needs to output 3.9 Nm

2.4 kg motor needs to achieve 2.4 * 0.2 + 3 = 3.48 Nm/kg

This requires 3.48 * 2.4 = 8.35 Nm

What's wrong with that?

Well, what this means is that a 2.4 kg motor needs to perform better than two 1.2 kg motors, meaning that it is not 'allowed' to put 2 motors on one axle (which doesn't make sense).

[Miles]

Why would you want to do that? Of course, 2 small motors won't perform as well as one big motor....

The whole point of the calculation is to allow for the advantage gained as motor weight increases. This means that you are leveling the field for motors of differing weights, within each weight category.

Of course, you could dispute the level of advantage we've allowed for....

[Miles]

Of course, you could dispute the level of advantage we've allowed for....

Suppose we changed it to 0.1 * motor weight + 3.2 ?

1.2kg motor needs to output 3.96 Nm

2,4kg motor needs to output 8.25 Nm

Is this more realistic?

[Miles]

As we also have the three weight classes, now, I think it would be quite sensible to start with a low value for the multiplier.

Any objections to: 3 + 0.1 x motor weight in kg, for the specific torque in Nm/kg ?

Anyway, it's all a bit academic, at the moment....

[Lebowski]

As we also have the three weight classes, now, I think it would be quite sensible to start with a low value for the multiplier.

Any objections to: 3 + 0.1 x motor weight in kg, for the specific torque in Nm/kg ?

Anyway, it's all a bit academic, at the moment....

how many peoplle have ever build a motor from scratch ?

[Miles]

how many peoplle have ever build a motor from scratch ?

You

[Arlo1]

And me

[Lebowski]

farfle?

I'm now coming up on one year commuting to work with my motor, about 5000 trouble free km's

[Arlo1]

Lol yeah mine was 100% troubble with the iron powder epoxy but a fun project and I will return to it.

[Farfle]

Sadly I don't think I am eligible, as I only have peak dyno numbers. If I were to hazard a guess, I would say that its good for 160-190 phase amps continuous which would leave me at 58-69nm. it weighs 15Kg, so if my WAG continuous numbers are close, I am at 3.8-4.6 Nm/Kg. No idea where that puts me at the current contest rules.

[Miles]

Using 3 + 0.1 * motor wt. you'd need to be able to sustain 4.5 Nm/kg continuously.

Using 3 + 0.2 * motor wt. you'd need to be able to sustain 6 Nm/kg continuously.

Considering that your motor is far from being optimised for weight ...............

[Farfle]

Using 3 + 0.1 * motor wt. you'd need to be able to sustain 4.5 Nm/kg continuously.

Using 3 + 0.2 * motor wt. you'd need to be able to sustain 6 Nm/kg continuously.

Considering that your motor is far from being optimised for weight ...............

Awesome, it doesn't look half bad. I could probably shave 2-3kg off of it without too much work, but on top of all of the structural modifications, Its copper/iron ratio is not set up for maximum continuous power, more towards burst power without saturating.

[Miles]

So, shall we start off with the 0.1 multiplier, then?

[Farfle]

So, shall we start off with the 0.1 multiplier, then?

.1 is pretty achievable for a novice with some preparation, but if we are shooting for something special, then .2 should be the metric.

(It also gives me something to shoot for with the next motor )

[Miles]

It's the base number that we'll be increasing to "raise the bar". The weight multiplier factor will be adjusted to smooth the transition between the weight groups. So, it's more related to addressing the advantage of scale.

[Farfle]

It's the base number that we'll be increasing to "raise the bar". The weight multiplier factor will be adjusted to smooth the transition between the weight groups. So, it's more related to addressing the advantage of scale.

Then I say that .1 is a great place to start

[Miles]

Ok. I'll make the change. No more changes after this.....

[KarlJ]

most efficient is going to be an axial flux design......, quite simple to DIY also.

EG use an otherwise destroyed motor as a base neo's on the outside coils on the inside
pick magnets you can get at reasonable money
http://www.fieldlines.com/index.php?act ... 2538;image
pick big wire = power handling without melting
no laminations to saturate = pump in as much power as you can, keep an eye on the temps.

a 5kW wind turbine motor will run 50kWW in short bursts no problems similar RPM's required too match made in heaven.