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20th June 2015, 05:18 PM #76
If you use a flat pulley with lips the belt will jump or bounce from one side of the pulley to another and destroy itself in an alarmingly short time.
The 1deg taper and blend works very well, if you go with a more aggressive crown they tend to ruin the belts by stretching the middle of the belt and you and up with very little belt actually gripping the pulley.1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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20th June 2015, 06:01 PM #77Philomath in training
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Just to add to Ewan's comments Simon, when I worked out the necessary crowning for the pulleys I made, (because I was not sure that I would fit the large one on the lathe), I worked out what the tangent angle would be if I wanted to do some trick stuff on the mill. Turned out the tangent angle was around 1 degree. If I'd crowned the pulley on the mill it would have been very similar too - the cutter would have removed around a third of the face and then I would have had to blend it.
The edges on my pulleys are only there to prevent the belt flipping off when things are not rotating - other than that I expect the belt will ride on the top of the crown, even if it is only a fraction of a mm.
Michael
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20th June 2015, 06:35 PM #78GOLD MEMBER
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Thank you gentlemen, I'd wondered for awhile why some pulleys have both flanges and crown.
Stuart
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20th June 2015, 06:41 PM #79SENIOR MEMBER
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The worst that can happen is you will fail.
But at least you tried.
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20th June 2015, 10:05 PM #80GOLD MEMBER
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Ueee, Michael & Rob, Thanks for the info. So a mathematical approximation to a crown will satisfy the belt then. 1 deg sloped either side from the middle and then nick the top off to produce a symmetrical trapezoid? Simon
Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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20th June 2015, 10:40 PM #81Philomath in training
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Rounded - a corner may cut the belt.
Michael
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20th June 2015, 10:51 PM #82
Yeah round it over the best you can. I have been making rubber wheels so it is pretty easy to do, in ally it may take a bit more time.
1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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21st June 2015, 11:02 AM #83SENIOR MEMBER
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I had to sleeve and crown the largest pulley on the intermediate shaft for my old Schaublin 102.
It was in steel, and I did it by eye, free hand.
I just crowned it until it looked right (same as the rest), but you certainly don't need much to centre a belt.
I did it in small steps starting from each side (did both sides then moved up), worked towards centre (same principle as making a cone), then smoothed out the ridges in one freehand pass with a finishing cutter, and used a fine file and old belt sanding strips to finish it off.
I think I used a 35 degree profiling cutter, same as for making "V" pulleys.
Pretty easy job - came up great.
I practiced on a bit of scrap first, so maybe do that to get the depth/process right.
The pulley surface should be rounded, so I don't like your nip off the top idea,
RobThe worst that can happen is you will fail.
But at least you tried.
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21st June 2015, 12:13 PM #84GOLD MEMBER
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Thanks Rob,
I see what you mean, I have been thinking a bit about it this morning. I have been trying to approach this from a mathematical POV. A height difference of 1/8" per foot equates to a segment of a circle with a radius of approx. 3750mm. Not sure how that helps me but it's a start. I'm trying to work out the DOC and angles required to approximate a circle of radius 3750 with 5 flat edges to approximate the crest. Then smooth out with emery.
I have just worked out the angle of the tangent from the edge of each side to be 2.67 deg. That's a fair bit off the 1 deg that you guys estimated. I'll have another look…...
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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21st June 2015, 12:46 PM #85SENIOR MEMBER
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Hi Simon.
I never subscribed to the one degree theory. I don't know where that came from.
Certainly the curvature on my C0 Waldown is greater per width, than my old Schaublin.
Modern thin section drive belts can wrap around any sized curvature really.
They are not like the old leather and stiff belts which will ride up on the crown.
The belts on my C0 are actually made of a type of woven fabric (original) and as flexible as a sock .
So I wouldn't get too hung up on the degree of curvature being x or y if you use a modern polyester or specialised belt (within sensible limitations).
RobThe worst that can happen is you will fail.
But at least you tried.
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21st June 2015, 12:59 PM #86GOLD MEMBER
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Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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21st June 2015, 05:48 PM #87GOLD MEMBER
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I just took the time to have a good look at the flat belt pulleys on my T&C grinder. Looks like im over complicating the whole thing! These pulleys only have two surfaces, ramped up to the centre and then down. The high spot in the middled is rounded but they are essentially flat with the high spot being about 1.5mm higher tgan the sides. These pulleys are about 1" wide. I measured the angle at roughly 3.5 deg. Think ill just copy these.
Edit: Was having trouble attaching pics from my mobile. Here are the pulleys on the t&c grinder:
20150621_162845.jpg20150621_162658.jpgGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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22nd June 2015, 12:32 AM #88.
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22nd June 2015, 12:54 AM #89GOLD MEMBER
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22nd June 2015, 09:56 AM #90GOLD MEMBER
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Thanks Bob.
Hi Kryn. Its a starrett bevel gauge. I inherited it from my Dad. Do not when or where he got it. It has a name on it A. G. Flood but thats not my dad.Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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