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Gerald_D
Registered
Username: Gerald_d
Post Number: 18
Registered: 11-2005
| | Posted on Thursday, December 15, 2005 - 10:03 pm: | 
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No cheapy turnbuckles - the spring length/size is correct for 25lbs force
PS. Please don't blame me for getting the stepper motor into the state you see it above. It was supplied to me like that by ShopBot who claimed it was only slightly used. The shaft still has to be repaired before I can get a gear on - looks like it has been hit on the end with a hammer. Buying "slightly used" motors without being able to check them out first is a bad idea.
The plate rotates on a Teflon washer, plus it is stabilised by a second Teflon slide towards the spring.
This is the "non-motor" side of the y-car - a dummy idler roller is in there to make a proper hold-down:
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dvanr
Unregistered
| | Posted on Thursday, January 12, 2006 - 03:03 pm: |
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The chinese turn buckles may have a purpose other than tensioning to the right force. They may be there to keep spring size to a minimum.
By using a larger spring you increase the capacity to store mechanical energy over a longer distance. This might cause problems on fast stops and starts. Translating into rough cuts. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 25
Registered: 11-2005
| | Posted on Thursday, January 12, 2006 - 04:15 pm: |
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I don't think that such exotic considerations (energy storage) were made when the spring system was designed. Because of all the fiddling with the pinion gear sizes, something had to be done to make the spring anchor point adjustable, and the inexpensive turnbuckle was it.
The standard short/fat SB spring is too "stiff" for adjustment - a small bit of dirt on the pinion increases the force drastically. While a small amount of nut loosening takes the force right off. My long/thinner spring could probably store the same amount of energy, but it is much less temperamental, and not prone to incorrect adjustment. |
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