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 Chief Delphi Clamping wheel hubs
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#1
02-28-2004, 10:20 PM
 sanddrag back to school ;-) FRC #0696 (Circuit Breakers) Team Role: Teacher Join Date: Jul 2002 Rookie Year: 2002 Location: Glendale, CA Posts: 7,565
Clamping wheel hubs

Say you have a wheel with no hub, it is just a plain bore. Then say you make a couple "drive flanges" that are made out of 3/16 plate They are circular in shape, have a keyway bore, and 6 evenly spaced holes in a circular pattern. If you put one of these on each side of the wheel and placed bolts through the six holes (matching holes would be in the wheel), the flanges would be locked with the axle by key and the wheel would be locked with the flanges by clamping force when the bolts and nuts are tightened . Now, my question is, is the clamping (friction?) force alone of these "drive flanges" enough to drive the wheel without it slipping. Is this method ever used for driving things?

Is there any formula to determine how much force it would take to make the wheel slip from the flanges given the bolts are torqued to a given amount?

Thanks.
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#2
02-28-2004, 10:23 PM
 jacob_dilles Registered User AKA: theshadow FRC #0620 (WarBots) Team Role: Mentor Join Date: Jan 2003 Rookie Year: 2003 Location: Vienna, VA Posts: 245
Re: Clamping wheel hubs

from what it sounds like your bolting 2 plates on either side of a unkeyd wheel. is this right? because if that is what your saying, the bolts, and the friction of the 2 plates pressing ageinst the wheel would deffently be enugh to drive it.

sorry if i missed the point totaly
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#3
02-28-2004, 10:27 PM
 sanddrag back to school ;-) FRC #0696 (Circuit Breakers) Team Role: Teacher Join Date: Jul 2002 Rookie Year: 2002 Location: Glendale, CA Posts: 7,565
Re: Clamping wheel hubs

Quote:
 Originally Posted by jacob_dilles from what it sounds like your bolting 2 plates on either side of a unkeyd wheel. is this right? because if that is what your saying, the bolts, and the friction of the 2 plates pressing ageinst the wheel would deffently be enugh to drive it. sorry if i missed the point totaly
You actually totally got the point. The wheel would be unkeyed but the hubs would be keyed. The hubs would clamp the wheel. Don't think about the bolts going through the wheel to drive it (since that part is very thin plastic), think only about the friction of the clamping force of the two plates.

How do you know it would be enough?

Also, does surface area have anything to do with this?
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#4
02-28-2004, 10:34 PM
 jacob_dilles Registered User AKA: theshadow FRC #0620 (WarBots) Team Role: Mentor Join Date: Jan 2003 Rookie Year: 2003 Location: Vienna, VA Posts: 245
Re: Clamping wheel hubs

well if the bolts arent in direct contact...

it depends on a lot of things. first of all, the 2 surfaces. if there both plastic then its gonna take more force then steel to get them to stay. if you want it to be pure friction, its gonna be the more torque the better. roughing up one or both surfaces will reduce the amount of torque needed. genraly speaking, if your dealing with metal a half turn past hand tight should be okay for 1/4, a 3/4ths a turn past for 3/16. if its lexan or plexi, your gonna have to be realy torquin down, maybe 2 or 3 turns past hand tight.

but friction can ALWASE slip, especialy if there is an eccesive (and usaly unplaned) force in a parrallell direction to the planes that the friction is acting on (sry a bit confusing). reinfocing with pop rivits or even 1 or 2 roll pins is never a bad idea. hope everything works out.
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#5
02-28-2004, 10:38 PM
 sanddrag back to school ;-) FRC #0696 (Circuit Breakers) Team Role: Teacher Join Date: Jul 2002 Rookie Year: 2002 Location: Glendale, CA Posts: 7,565
Re: Clamping wheel hubs

The drive plates will be 3/16" thick aluminum and the wheel is polypropelyne plastic
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#6
02-28-2004, 10:49 PM
 jacob_dilles Registered User AKA: theshadow FRC #0620 (WarBots) Team Role: Mentor Join Date: Jan 2003 Rookie Year: 2003 Location: Vienna, VA Posts: 245
Re: Clamping wheel hubs

whats the (effective) diamater of the plate? or more relevently, what is the surface area that the aluminum has to grip? i.e. 1sq" or 15sq"s?

i couldent tell you off the top of my head what it is, but there is an equation for friction coeficents between diffrent materials. however it sounds like it would work. some advice however, roughin (sp?) the aluminum (not the plastic) with some hevey grit sandpaper. also, consider some type of centering device depending on how much weight is on the wheel. do the plates have to keep it trued also? or can the unkeyed hub bear weight. if your just using it for drive, youd be suprised what 30 or 40 ft-lbs of torqe on some bolts can hold. however depending on the traction of the wheel you may need more bolts...

also there have been some problems (do a search) with people keying aluminum plate. the steel keystock rips right thru the aluminum key, making the slot wider and wider untll it becomes unuseable. a steal shaftcoller epoxyd or heat fitted onto the alumunum would do you good.
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#7
02-28-2004, 11:02 PM
 sanddrag back to school ;-) FRC #0696 (Circuit Breakers) Team Role: Teacher Join Date: Jul 2002 Rookie Year: 2002 Location: Glendale, CA Posts: 7,565
Re: Clamping wheel hubs

there is approximately 1.3 sq inches of area that the force is applied to on each side of the wheel. The center section of the wheel is a sort of spoked design, that's why the area is so low. You can see a similar wheel here http://www.northerntool.com/images/p.../155123_lg.jpg I will not be using the bearings in mine.

The drive flanges do not have to center or true the wheel, I have that taken care of. As for the keyways enlarging, I have that under control also.
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#8
02-29-2004, 12:20 AM
 jacob_dilles Registered User AKA: theshadow FRC #0620 (WarBots) Team Role: Mentor Join Date: Jan 2003 Rookie Year: 2003 Location: Vienna, VA Posts: 245
Re: Clamping wheel hubs

hmm. 6 bolts... torqued down to 30-40ft/lbs. it should work......... i think.

to improve chances of sucess:
*if you roughing up the aluminum, maybe make small ridges in it with a drimel or similar tool so that it can realy grip the plasitc it should work.
*some super grippy rubber inbetween the aluminum and the plastic might help
*silicon gasket material, waterproof cauk, or just plain epoxy would make it a great deal stronger
*an alternitive to adhesive is to drill about 50-100 small holes ( VERY small ) in the aluminum where it will contact the plastic. that way when the tourqe is aplied the plastic will sqeeze into the holes and make it grip a lot better.

and for torquing the bolts.... there IS a right way to do this. say there aranged like this:
**1*2**
*3***4*
**5*6**
you first hand tighen them all. then tourqe #1, #6, #4, #3, #2, #5. its almost like a head gasket. hope this helps...
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