dhutch
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| posted on 18/4/12 at 10:34 PM |
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Pulleys - Need a supplier of some good ones!
Yes, I need some pulleys. Strong and cheap, sized for 6-8mm rope with a diameter around 30-50mm. Any suggestion considered.
I've had a bit of a look and found a few climbing pulleys that are getting there, or industrial blocks and sheaves that would do it if i wanted
100, and sailing kit thats extra ordinarally expensive but nothing quite there yet.
Its for the steering of a narrowboat with wheel steering, where I'm planning to use high 6mm dia performance dyneema rope as a compromise
between strength and compactness, as a similar strength steel cable has a much large bend radius and without a lot of work I'm limited to
getting it fit in the space of the old system, which used 3mm stainless steel and nylon pulleys, which wasn't up to the job long term.
I need three singles and two doubles (or 7 singles) total budget around £100.
*edit for late night spelling
Daniel
[Edited on 19/4/2012 by dhutch]
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James
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| posted on 18/4/12 at 10:45 PM |
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Our very own Flak Monkey does pulleys for people. Worth a message to him I'd have thought. 
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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PSpirine
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| posted on 18/4/12 at 11:18 PM |
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Don't see why you can't just use normal marine pulleys.. ironically they're even intended for boats! 
BRAND NEW Barton size 3 Reverse shackle block / pulley | eBay
7 of those doesn't break your budget? 45mm diameter up to 10mm rope?
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dhutch
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| posted on 19/4/12 at 07:44 AM |
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quote:
Originally posted by PSpirine
Don't see why you can't just use normal marine pulleys.. ironically they're even intended for boats!
7 of those doesn't break your budget? 45mm diameter up to 10mm rope?
Mainly due to me nervousness of there not being strong enough.
That pulley which is in line with most others with just under 400kg max load and 'breaking load' of only 770kg. The wheel gives a
mechanical advantage of around 10:1 and at full lock and full power your just about hanging on as hard as you can which have reckoned at being round
50kg force. That gives 500kgf into the rope, 700kgf into a pulley that's deflecting the rope at 90degrees.
Obviously these peak loading's don't happen that often, maybe once a day (circa 35 times a year) and typically with the wheel held
statically, maybe 3-4 occasions per day of applying half that force with movement, normal running forces being a tenth of that. But while I'm
open to advice in my book that's still leaving bugger all margin on a critical system that I'm trying to engineer more trust and
durability into.#
The pulleys will covered as they are effectively inside, and the boat rarely used on salt water/brackish water so corrosion etc isnt a huge issue.
I'll PM flakmonkey and see what he says.
Daniel
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Peteff
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| posted on 19/4/12 at 08:38 AM |
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If you have more than one pulley isn't the load shared amongst them ?
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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