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Discussion
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27-08-2012 21:52
Camren
Re: pic: Delrin Poly Cord Pulleys
Interesting I assume those are machine lathed. But from what material?
27-08-2012 21:59
Josh Fox
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by Camren
Interesting I assume those are machine lathed. But from what material?
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27-08-2012 22:03
Garret
Re: pic: Delrin Poly Cord Pulleys
| Interesting I assume those are machine lathed. But from what material? |
27-08-2012 22:03
Alex Cormier
Re: pic: Delrin Poly Cord Pulleys
Photo title says delrin. It's a good all around plastic that doesn't wear when using polycords. It's a bit heavy though.
27-08-2012 22:08
Camren
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by Garret
I assume delrin, because of the title.
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Originally Posted by Alex Cormier
Photo title says delrin. It's a good all around plastic that doesn't wear when using polycords. It's a bit heavy though.
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27-08-2012 22:39
theawesome1730
Re: pic: Delrin Poly Cord Pulleys
Hope that there is never enough friction generated to melt/burn the Delrin, the fumes/smoke it gives off is like tear gas
27-08-2012 22:45
Mk.32
Re: pic: Delrin Poly Cord Pulleys
Hello all,
These are machined from Delrin 1inch stock.
They weigh about .3lbs each; which we found to be reasonable for the pulleys and a LOT lighter and cleaner then our last solution.
Delrin is pretty stiff stuff and as poly cord pulleys shouldn't ever experience friction to really melt/burn it.
28-08-2012 08:11
Jared Russell
Re: pic: Delrin Poly Cord Pulleys
What is the OD of the grooves? No worries about the rod deflecting under tension?
28-08-2012 08:54
Brandon Holley
Re: pic: Delrin Poly Cord Pulleys
To go along with Jared's questions, what diameter round belting (polycord) are you using? If the pulleys are machined from 1" diameter stock, you may be very far below the suggested minimum pulley size.
-Brando
28-08-2012 10:37
JesseK
Re: pic: Delrin Poly Cord Pulleys
Most polycord has a minimum pulley diameter, and the pulley diameter gets bigger as the cord diameter gets bigger. Exceeding the minimum diameter puts extra load on the motor driving it.
For example, the hollow Yellow Round Urethane belts my team likes to use (McMaster # 6567K56) has a minimum pulley diameter of 1.5". This year we were able to get away with a 1" diameter @ 3% cord stretch, given the gearing & power of the motors we chose. If we used a weaker motor or faster gearing, we would have probably enforced the 1.5" diameter design parameter. We also relaxed the belts overnight and in between competition so they didn't wear faster than expected.
Just something to keep in mind.
28-08-2012 12:01
Mk.32
Re: pic: Delrin Poly Cord Pulleys
The ID of the pulleys are .64 in.
We are using a smaller diameter then what was recommend but from past experience not have a lot of problems with it.
We are going to put these in later today, and I will report back about any problems.
28-08-2012 14:18
topgun
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by JesseK
For example, the hollow Yellow Round Urethane belts my team likes to use (McMaster # 6567K56) has a minimum pulley diameter of 1.5". This year we were able to get away with a 1" diameter @ 3% cord stretch, given the gearing & power of the motors we chose.
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We have only used the solid round belting but I am wondering if anyone can give a quick pros/cons of solid versus hollow.
- T
28-08-2012 14:58
IndySam
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by topgun
Doesn't the hollow round belting flatten out when installed? Have you had trouble with the little connectors coming out?
We have only used the solid round belting but I am wondering if anyone can give a quick pros/cons of solid versus hollow. - T |
We have used hollow belts more than a few times and the only times I have have had one separate at the connector was when belts were installed to loosely. They kind of work like finger cuffs, harder you pull the more they hold on.
The only reason we have used hollow belting was because it was easy, no other big reason. They are both great. One advantage to hollow belting is it can be removed and replaced without removing rollers. Solid belting gives you more choices of belt thicknesses and will generally allow smaller roller diameters.
28-08-2012 16:50
Garret
Re: pic: Delrin Poly Cord Pulleys
| Doesn't the hollow round belting flatten out when installed? Have you had trouble with the little connectors coming out? |
28-08-2012 18:23
Mk.32
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by Garret
In 2011 when we used 1/4" belting for our claw we had no problems with the connectors, however this year with the 3/16" belting it seemed as if we were always losing at least 1 belt because a connector came undone. I would attribute this to more likely too much tension on the belts but nevertheless something to be aware of.
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29-08-2012 01:13
Mk.32
Re: pic: Delrin Poly Cord Pulleys
So my worst fears as been confirmed, the .6 ID of these pulleys make them to flexible. Under the load of 4 cords there is about an 1/8 of an inch of deflection which makes them very stiff to turn. We are switching to 6061-T6 and with an ID of .66.
29-08-2012 01:51
artdutra04
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by Mk.32
So my worst fears as been confirmed, the .6 ID of these pulleys make them to flexible. Under the load of 4 cords there is about an 1/8 of an inch of deflection which makes them very stiff to turn. We are switching to 6061-T6 and with an ID of .66.
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1.5" diameter x 0.040" to 0.063" wall thickness aluminum tube works great for polycord rollers.
29-08-2012 01:55
R.C.
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by artdutra04
If you can, go with a much larger OD and use round hollow tube for the roller material.
1.5" diameter x 0.040" to 0.063" wall thickness aluminum tube works great for polycord rollers. |
Such as McMaster: http://www.mcmaster.com/#87235K34 (comes in black btw
)We used 1.25 OD X .060 wall. It allowed us to press in a FR8 Bearings. So we drove one roller and made the rest dead/pressed in bearings.
-RC
29-08-2012 01:56
AdamHeard
Re: pic: Delrin Poly Cord Pulleys
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Originally Posted by artdutra04
If you can, go with a much larger OD and use round hollow tube for the roller material.
1.5" diameter x 0.040" to 0.063" wall thickness aluminum tube works great for polycord rollers. |
If you can drop down to 1.25" 1/16" wall the bores can accept an FR8 bearing too, very convenient.
29-08-2012 09:15
JesseK
Re: pic: Delrin Poly Cord Pulleys
If you want to avoid grooves altogether, a plate of finger guides may work. See the bottom-left of this photo:
http://www.chiefdelphi.com/media/photos/37572
02-09-2012 12:52
BlacksmithWoods
Re: pic: Delrin Poly Cord Pulleys
Nice, these look great! I wish I had those. I had to bang those out made out of wood on our homemade lathe. http://www.chiefdelphi.com/forums/sh...Homemade+Lathe
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