DC Motor Torque

[motiondave]

Mod remark: This topic is a result of a discussion going on in my build topic. I think it's interesting for some of you to read so I decided to split the discussion into this topic.

Remember, some torque figures are stall, so they may be higher. My big motors are 20nm standard, stall torque would be a lot higher.
A standard wiper is usually about 6-10 nm, not sure if thats stall or normal figures though.

[floriske]

@motiondave:

Regarding your motors: I've been in touch with a manufacturer of those motor types and got the datasheet from them: The stall torque is 30-45Nm according to that.
But beware that these Chinese manufacturers tend to lie about specs. Someone else I've been taking to with extended DC motor knowledge metioned that basically a 12V 180W motor of this type with this gear ratio can have only around 10-15 Nm nominal torque.

[motiondave]

Floriske, well something is not correct then as I have run wipers in the past from large passenger vehicles and now I run these big worm gear motors.
Let me tell you, the big motors KICK WAY MORE than any wiper.
Sorry to sound miffed, but torque figures are really in accurate.
I would not suggest these motors unless I * And , no I am NOT in anyway getting any benefit from any sales whatsoever.
All I can say is that a motor that lists 60w power and a motor that lists 180w power, well, wouldnt one be more powerful than the other? Not to mention they are BIGGER in size than wipers?
So if these motors have only 12-15mn torque, then show me a wiper that exceeds the motion I get them.
http://www.youtube.com/watch?v=ZbN8XF027lc , show me a wiper that creates this sort of motion.
I just built a seat mover with motors just under the back for a chap using the big motors and let me tell you, they moved me a hell of a LOT better than a wiper seat mover I built in the past.
I have nothing against wipers, I built several rigs using them to great success! They are cheap and easy to find. I now use bigger motors because I have spend a LOT on time working with them.
Cheers, David.

[floriske]

@motiondave: didn't mean to offend you or your motors in anyway! Was just sharing what I was told.

I've seen your motors at work and they def. give better motion than normal wiper motors!

Some more research leads to the following:

• (hp / RPM) x 5252 = Torque in foot-pounds

• 1 ft lb = +/-1,356Nm

• 1 hp = 746W

Let's say a gearbox has no friction loss, than the total formula becomes:

• ( (Watts/746) / RPM ) x 5252 x 1,356 x gearbox ratio

In case of your motors:

Motor Speed: 3600 RPM/160-180 RPM at Gearbox (resulting in a +/-1:20 gearbox)

• ( (180/746) / 3600 ) x 5252 x 1,356 x 20 = 9.5 Nm nominal Torque

[motiondave]

wipers usually run at 50-60 rpm anyway
Besides that, your sim works great!

[value1]

• What about having a look in the Performance Curve of the Dayton G180-12 found at the bottom of the specification page?
The maximum efficiency (48 %) is at 18 A. There the torque is indeed around the mentioned 9.5 Nm.
However at maximum power output (50 A) the torque is 26.4 Nm.
The stall torque is even higher with 32 Nm.
At the maximum amps of ~30 A that the JRKs can handle it's about 16 Nm.

And these are MEASUREMENTS not just theoretical calculation.

[floriske]

That's what I wanted to make clear and why I clearly stated "Nominal torque", (since you mentioned your motors being "20Nm standard") just wanted to make clear (like you said as well) that specs tend to mention "maximum Torque" as Torque which might fool people into thinking it is the nominal torque whilst it isnt

As mentioned, I know your motors are a lot better! In fact I just ordered the comparable motors and gearbox from ebay for my sim

It's just that I wanted to make clear that the torque mentioned at different motor types might vary a lot because an honest manufacturer mentions nominal torque, but a lot mention maximum torque or even stall torque which can make it difficult to compare motors.

Think it is a good idea to split these posts into a seperate topic in the motors section

[motiondave]

• What about having a look in the Performance Curve of the Dayton G180-12 found at the bottom of the specification page?
The maximum efficiency (48 %) is at 18 A. There the torque is indeed around the mentioned 9.5 Nm.
However at maximum power output (50 A) the torque is 26.4 Nm.
The stall torque is even higher with 32 Nm.
At the maximum amps of ~30 A that the JRKs can handle it's about 16 Nm.

And these are MEASUREMENTS not just theoretical calculation.

Just for reference, I run my JRKS at 30 amps continuous, not peak, peak is close to 38 amps. http://www.youtube.com/watch?v=ZbN8XF027lc show me a wiper that moves like this and I will buy it!

[value1]

Just for reference, I run my JRKS at 30 amps continuous, not peak, peak is close to 38 amps.

So that would be a lovely 21Nm then!
Anyway: how do you measure the amps the jrks are gulping? I haven't found a gauge that can measure such high currents reliably and accurately (and affordably).

[floriske]

@motiondave:

I've just ordered the motors and gearbox from ebay and was wondering what PID settings you are using to "tame" your motors? (PID is new to me so any "Reference" is good to have)