Placement of Slipper Clutch

[mechanix]

I'm designing a dual motor, single-stage reduction drive for a downhill bike and am wondering if it would be acceptable to place the slipper clutch at the hub. The reason I want to put it at the hub is so I don't have to install two slipper clutches, one on each motor. I know it will require a tighter clutch because there's more torque at the wheel due to gear reduction, that's not a problem. Is there any other reason I would want the clutch to be at the motors instead of the hub? Thanks!

Joel

 

[johnrobholmes]

You should be able to run a smaller clutch at the motor because of the higher RPM, but I gather you already know that.

Other than the higher torque at the hub, there shouldn't be any other complications.

 

[MitchJi]

Hi,

A major advantage of a Slipper Clutch is driveline protection from excessive and uneven loads. If you put it at the hub you lose those advantages (unless the hub is the weak link).

For driveline protection the closer to the motor(s) the better.

 

[katou]

Figure your theoretical torque ratings after reduction, and see if the "torque limiting clutch" that you want will handle it. They are rated for the torque they can handle, so it should be a fairly quick trip over the McMaster website.

Katou

 

[recumpence]

You do not need two clutches for two motors. I would recommend the motor both run to one clutch on the jackshaft, unless you are not running a jackshaft.

Matt

 

[mechanix]

Thanks for all the replys, here's a picture that shows roughly how it's going to look:

 

[MitchJi]

Hi,

I'm pretty sure Matt posted that anything smaller than 14t was too noisy for a primary drive sprocket. With a secondary drive sprocket of 11t D's Kona sounded acceptably quiet.

This is what Gary said about an 11t drive sprocket (I'd be surprised if changing from 11t to12t would make much difference):

WIn the brief time I used it, I had no problems at all, but this 3220 "direct drive" setup just makes way too much racket, for my tastes...

...I hate the direct drive setup I have now because it just makes such a horrible racket...

...The problem with trying to do a direct drive ratio of 8 or 9:1 is that the drive sprocket needs to be small and that means it will make a lot more racket...

...At some point I'm going to change my 11t motor sprocket to a 12t, which will bump the top speed in 1st to about 20 mph. This should also reduce the horrible racket my setup makes. That is the biggest problem with not having the belt drive 1st stage, it makes a horrible amount of noise, which is made worse by the small 11t sprocket...

...with the "direct drive" setup I did with the 3220 and the large #35 sprocket. That too sounded like somebody dumped a bucket of bolts into the spin cycle of a washing machine...

... due to the chordal effect. It is hard for a chain to get around a sprocket that has fewer than 11 or 12 teeth. It ends up sounding like bucket of bolts in a washing machine...

 

[briangv99]

Hi Joel,

I'd go with LFP's sprocket layout, no need for an idler and better chain wrap

unless you have customs parts made, I think the only off the shelf slipper clutches that will work will be on the motor side

Tapholov #25 chain bike with 11T sprockets doesn't seem too noisy in the videos he's posted

Brian

 

[mechanix]

Mitch: Thanks for bringing that to my attention!

I'll have to go back to my original plans of using the rear swingarm pivot as a jackshaft, and put the slipper clutch on that. I'll post some CAD drawings when I get some time after finals are done with on thursday.

Joel