Alternate Wiper Motor approaches

[RufusDufus]

One of the biggest challenges for a newcomer like myself, is working through the enormous amount of information that exists to come up with a design that suits one’s own specific needs within the many constraints of cost, quality, capability, time, personal preference, etc. At the same time most DIYers gain satisfaction from adding our own personal touches and sharing knowledge back to the community.

In doing this I have become curious as to the way the “wiper motor” designs have been implemented and wanted to pass on some thoughts and associated information in the hope others may be able to expand my knowledge.

Please note none of this is criticism of the designs, I am just trying to understand the key drivers for the approaches taken!

TOPIC: Translating rotational motion into simulator movements…

It seems most wiper motor designs translate the rotational position of the wiper motor into simulator movements using a lever and connecting rod arrangement (as shown in the diagram below)

DIAGRAM 1 (Sorry having issues uploading images to gallery - will add later)

The effect of this is that a constant rotational (wiper motor) speed does not translate into a constant simulator movement. (Refer diagram below) The simulator movement will be greatest (and hence fastest) when the connecting rod and lever arm are closest to a 90 deg angle – and – the simulator movement will be almost negligible (and hence slowest) when the connecting rod and lever arm are in alignment. This of course assumes that the motor speed is not specifically adjusted to accommodate this.

DIAGRAM 2 (Sorry having issues uploading images to gallery - will add later)

So my questions are:
1. Is this effect actually significant in the designs?
2. Does the motion control software address the issue by changing motor speed?
3. Is it just the easiest and most cost effective solution that works well enough?
4. Are there any other design approaches that have been used with wiper motors?

Some general thoughts:

Have there been any designs that use a chain/sprocket or cable/pulley or rack/pinion arrangement to translate the rotational movement of the wiper motor into simulator motion? (one possible example shown below).

DIAGRAM 3 (Sorry having issues uploading images to gallery - will add later)

This creates a lot of alternate design issues compared to the standard lever/connecting rod arrangement however I'm looking for those with experience with the designs to comment if they think the advantages would out way the disadvantages?

Some Specs of the SCN5:
- Maximum Speed: 400mm/s
- Maximum Thrust: 100N / 10.2kgf

Some Specs of the SCN6:
MODEL 1
- Maximum Speed: 200mm/s
- Maximum Thrust: 200N / 20.4kgf
MODEL 2
- Maximum Speed: 100mm/s
- Maximum Thrust: 500N / 51kgf

Specs of the wormdrive referred to by motiondave:
- Torque: 20Nm
- No Load Speed: 180rpm
- Rated Speed: 150rpm

Now if you have a pulley with diameter 50mm and run at rated speed of 150rpm that translates into a linear motion of 392mm/s which is very comparable to the high speed of the cheaper SCN5. The interesting thing is with a 20Nm torque using this diameter you get 800N of force (thrust) to the sim seat which is better than the slowest/most powerful SCN6.

Calculations for the above:
Linear speed of cable wrapped around a pulley:
In 1 second the pulley turns -> 150rpm / 60 secs = 2.5 revs per second
In 2.5 seconds the cable moves 2.5 times circumference of the pulley -> 2.5 * pi * diameter = 0.392 m/s (or 392 mm/s)
Forces generated through the cable where attached to the simulator seat:
Force (Thrust) in Newtons is the Torque / radial arm length -> 20Nm / 0.025m = 800N

With these calculations you can see the trade-offs that can be made:
If you halve the diameter of the pulley you will halve the linear speed but double the force you can generate from the motor torque. Another way of looking at it - the less work the motor has to do for the same load!
If you double the diameter of the pulley you will double the linear speed but halve the force you can generate from the motor torque. Another way of looking at it - the more work the motor has to do for the same load!
You can also use these formulas to the lever arm/connecting rod arrangements however they only apply when the lever arm and connecting rod are at right angles to each other. As they move further away from the right angle the linear speed drops and the force available increases.

Happy for any feedback (positive or negative)

[motiondave]

ok, a bit more technical than I can understand.
Wipers good but to slow.


http://www.motiondynamics.com.au/worm-d ... orque.html with a 100mm lever, according to Bobbuilt moves at 200mm per second or faster.
I run them with a 45mm ctc lever and they snap fast.
I have also re-motored brick actuators viewtopic.php?f=36&t=605 and apart form being FERKING expensive, I find the big worm gears for me do just as well.
Actuators harsher, motors more fluid.
I run the pololu JRK at 30 amps continuous easy.

Once you have uploaded pics, we can have a look at better answering your questions.
Cheers, David.

[RufusDufus]

ok, a bit more technical than I can understand.
Wipers good but to slow.


http://www.motiondynamics.com.au/worm-d ... orque.html with a 100mm lever, according to Bobbuilt moves at 200mm per second or faster.
I run them with a 45mm ctc lever and they snap fast.
I have also re-motored brick actuators viewtopic.php?f=36&t=605 and apart form being FERKING expensive, I find the big worm gears for me do just as well.
Actuators harsher, motors more fluid.
I run the pololu JRK at 30 amps continuous easy.

Once you have uploaded pics, we can have a look at better answering your questions.
Cheers, David.

Hi Dave, Yes those motors in the link are the ones I was doing the calcs for... I saw your reference to them in another post and thought they looked really good. Based on my calculations they are capable of outperforming the SCN5 and SCN6 - I could be wrong though

So if you have a 45mm lever on yours, am I right in guessing you get about 50-60mm total usable movement at the point you connect to the seat?
With a short lever arm like that you should be able to generate 880N at the rated motor torque. Have you found it works well with people of any weight?
Do you find they get very hot if you run the sim for a while?

I really like the look of these motors...

[motiondave]

Hello, I get about 70mm total movement up and down actually. But depending on where you mount the motors, at the head , you get more movement.
Now with a sim, it needs to be on a balance point and not supporting the whole thing on the motors.
With the motors at 650mm forward of centre point and spaced at 450mm ( too narrow) on my big foot mount motor sim, I found the lateral HUGE and longitudinal short and sharp, but nothing a good profile fiddle couldnt sort.
I had a bloke on it 6'6" at 140 kg and it moved him with ease.
The motors do get hot if you run them at full power in the Pololu JRK http://www.pololu.com/catalog/product/1393 I ran them at 34 amps continuous and 40 amps peak.
http://www.youtube.com/watch?v=zwHcnh6vdrA a 110kg , but under 6' driver buddy.
motors near my knees on a previous frame http://www.youtube.com/watch?v=ZbN8XF027lc more movement at head height.
I now run them at about 3/5 power and they still kick hard, but the motors only get warm.
Bobbuilt has the same motors, yet to be mounted to a sim , with 120mm ctgc levers ( i think) and he is astounded at how fast they move.
On a seat mover and or full frame mounted at the shoulders, they would be pure nasty!
I mount mine lower as I needed to build a shorter length sim.
Hope that helps.
Cheers, David.

[RufusDufus]

Great thanks for the info... Looks like it would be pretty hard to go past these motors - especially with an Australian supplier.

[motiondave]

Great thanks for the info... Looks like it would be pretty hard to go past these motors - especially with an Australian supplier.

to be honest, these are not ebay daytons, he had them specially designed and is stumped at how strong they are considering I WWWWAAAAYYYYY overdrive them, like from 200 watts to 540 watts.

[x1610]

What you,re telling is true!
Only those wormdrives have verry sunny figgers,they are reduced 20 times and give 20nm at rated speed they say.
Thats 1nm at 180 watt and 3600 rpm all other motors deliver half the torque at 180 watt and 3600 rpm.
8 amp rated at 24 volt means 192 watt and gives 180 watt output ,this is a efficienty from a other planet.
And we forgotten wormdrive efficienty
Making an actuator from them with 80kgf and 400mm/sec speed is to good to be true.
they are stronger than normal wipers,but to weak to make a 6 dof

[motiondave]

What you,re telling is true!
Only those wormdrives have verry sunny figgers,they are reduced 20 times and give 20nm at rated speed they say.
Thats 1nm at 180 watt and 3600 rpm all other motors deliver half the torque at 180 watt and 3600 rpm.
8 amp rated at 24 volt means 192 watt and gives 180 watt output ,this is a efficienty from a other planet.
And we forgotten wormdrive efficienty
Making an actuator from them with 80kgf and 400mm/sec speed is to good to be true.
they are stronger than normal wipers,but to weak to make a 6 dof

Thats right, good for a balanced frame, but not much good for lifting.
If you want lift, look at 12v boat winch motors on a 6 DOF
and they are way stronger than SCN5.
I have run them at 530 watts, way overdirven, they are tough buggers

[vicpopo]

Hi ,

Why you are not looking at AC motors?
There are enough projects whith this configuration.An AC gearmotor is not so expensive as you think , it's the most comon motor and you can find it everywhere.
You have to choose the right Inverter and a motion controler.
One of the big advantage is that it sucks low current and no problem to plug it at home with a good inverter ( single phase to three phase).
I'm agree with the fact that is no the global amount comparating to wiper motors but a lot of xsimer start with wiper motors and after move to other solutions.
If you start directly with ac motors , this solution could be competitive.

Regards

[motiondave]

12v 200w motor costs about $90
1 x JRK costs $99
cheap and simple.
240v doesnt cost much more, but you need to use an ard, hridges, inverters, 240v motors, etc.

Up to the original builder of course, but for a 2DOF balanced sim, 12v is always a good simple start.
as always its up to the builder what they want to use, we are just here to suggest.