Variable Speed Drives

[Spurs]

I am looking for advice on incorporating a variable speed drive into a special gear box design The overall ratio will be about 1500:1 with a range of operation between 1200:1 to 1800:1 with infinite adjustment capability.

The gear box will have an input speed coming form a 5.5 HP two cycle engine of 1500 RPM. The two cycle engine will be set to run at a constant speed.

I then want to mechanically make an adjustment (knob or lever) to dial in the desired output speed from my gear box.

Does anyone have any suggestions on how to go about this. I will be producing about 100 units a year of this type of gear box, so cost is a concern.

I have looked at variable speed pullies but am not happy with the life and maintenance.

If anyone has suggestion you can post them here, or contact me at ereit@rogers.com

 

[strokersix]

Spurs,

You might look at a company called Zero-Max. They make variable ratio boxes that use sprag clutches.

http://www.zeromax.com/products/drives/drivesmain.asp

Mike

 

[Spurs]

Thanks Mike

Does anyone know of any lower cost options or ways to build in this type of functionality right into my gear box?

 

[dvd]

Unless the load and operating conditions are very constant it seems somewhat optimistic to think that the engine will operate at constant speed. Why don't you use an adjustable governor on your engine to control the speed and then use a conventional gearbox?

 

[Spurs]

Dvd

We are trying to make very small adjustments on the output. At a 1500:1 gear box ratio, the changes in speeds purely on the input end are extremely difficult to control accurately.

We have tried this and are not please with the result.

We thought about DC drives but there power source is not available in the place where it will be operated.

 

[dvd]

It's hard to make worthwhile suggestions when I don't know the application details. Why aren't you using a gas powered generator and off-the-shelf electrical components?

 

[Spurs]

DVD

The problem is that the application is for farm equipment and there is no electricity available out on the fields. Most purchasers prefer mechanical components instead of electrical - its actually a selling point.

 

[Iskit4iam]

There are lots of ways to do this. All of them cost more than the belt drives you don't like. Your gearbox must be pretty exspensive. You might consider a low speed high torque hydraulic motor and a variable displacement pump. This may eliminate the gearbox and quite a bit of mounting and linkage cost making it reasonably economical.

 

[EnglishMuffin]

Have you considered PIV drives ? Of course, you may have included these in your "belt" category, although they use chains. They are widely used in agricultural, construction equipment etc. and I would say they are considered quite reliable.

 

[aviat]

Just a suggestion!
You may have a transmissibility problem with your belt drive. It is the rario of the amplitude of the excitation torque (size of pulses) to the amplitude of the output torque. I have seen other cases where people have problems connecting small engines to couplings etc. EPI at the site below explains some of the problems that occurs, even though it is not for the same installation. The I for the engine, gearbox, and whatever you are driving must be matched. If you are not already using it, a Rotex engine may be a good choice, as it is used to drive variable speed drives in ultralight A/C's and in other uses.

Hydraulics would also work, as mentioned before, and farmers are familar with the technology. Princess auto at the site below sells small engines with hydraulic pumps coupled to it. I don't know the reliability of the system. You would then drive the gearbox though a hyd. motor controlled by a flow control valve.

http://www.epi-eng.com/index.html

http://www.princessauto.com/PAcountry.cfm?CTRY=CAN&INF=home