Economics of transmission

I am not sure if I am going crazy or the world around me is:
I am going around trying to price out a project: To reduce motor speed using
a pulley system by 16:1 would cost me in pulleys alone $50 using a local
supplier (2 6" and 2 1.5" pulley). I have just come back from an auction
where one could buy several drill pressess for around $40. For this I have
two step pulleys, a motor, a shaft, some bearings etc.
Since when has it become cheaper to buy an assembled piece of second-hand
equipment and cannibalize it for parts rather than buy parts alone? Come to
think of it, it would not even have to be second-hand equipment: Plenty of
cheap small drill presses for
Reply to
Michael Koblic
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What you are paying for when you buy from local supplier, is for capital, space, and personnel needed to store all kinds of pulleys that are in stock. Spending $50 is a lot cheaper than driving around and wasting days in auctions.
Auctions have their place, but usually what you find there is not what you need immediately.
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My garage and back yard is a testament to that!
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Mine, as well.
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That's how I got my drill press. I really wanted the gears off of it and while looking at how to go about that task I realized that this old thing will probably work. Fixed it all up and then went back looking for gears from another source.
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Just be glad you don't have a huge barn and a 100 acre back yard. Plus a kid that learned "pack rat" from the old man.
I do buy things like old drill presses just for the motor pulleys etc. We took enough scrap to town out of the carcasses to buy a nice milling machine. \
Reply to
Karl Townsend
It's time vs money. You can buy new parts with known specs that all fit together and have the machine running quickly, or rebore pulleys and machine adapters for used stuff that may be too weak or damaged. When I build or repair a machine for industry I buy new to get the job done quickly. Second-hand parts are usually too risky for production machines though they may go into lab prototypes.
At home it's reversed, I adapt used stuff whenever possible except for important equipment like the vehicles and household plumbing or wiring. You have to consider your time and the likelihood and consequences of a failure. If this polishing machine (?) breaks down and makes you miss a delivery deadline then you could lose more than the $50.
The shaft, bearings and pulleys for my sawmill cost over $100 new. The mockup for the transmission was made from cheap used parts but when I calculated the torques for 5HP I realized I had to buy larger shafting and new steel pulleys.
Be glad you aren't buying new hydraulic components.
Jim Wilkins
Reply to
Jim Wilkins
"Just be glad you don't have a huge barn and a 100 acre back yard. Plus a kid that learned "pack rat" from the old man."
Boy do I know how that is. Barns are full of stuff and some stuff that should be in there sits out because there is no room. Try explaining to people that you have these huge barns and you don't have room sometimes to work on stuff inside. I can't tell you how many junk pieces of farm equiptment I have for parts for my "good" equiptment. The cost of 1 or 2 parts from a dealership can sometimes pay for the whole parts machine. I'm thankful that I have the room for them. Plus it saves downtime if I am baling hay or planting and something breaks. It never fails that something goes on a weekend after the dealership closes. Jesse
Reply to
You might have a motor already, and considered belts to be a good method to reduce the speed, sometimes they are not.
You might want to consider gear reduction instead. A gearhead motor, or a separate gear reduction box could be a better solution. Worm gear reduction results in an output shaft that is 90 degrees from the input shaft, and parallel gear reduction results in an output shaft 180 degrees from the input shaft.
You would need to determine how much final drive torque your project machine will require to select a suitably rated gearbox.
If this machine is related to the earlier questions about making a smooth 5" to 8" disk, the torque requirements shouldn't be very great, and a fractional horsepower motor with gear reduction would probably be sufficient.
The output of a gearbox shaft can be used as a direct-drive for the platter with a shaft coupler, or a chain and sprockets can be utilized to change the output shaft speed to optimum.
WB ......... metalworking projects
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One thing to consider in the import DPs is the quality of the pulleys. Many do not run as true as you might like. I suggest you chuck each into the lathe and clean it up before using it.
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Go to your local car dealer and check the sticker price of some particular car. Now, go to the parts department, and tell them you want to buy that same car as all separate parts, and assemble it yourself. You will find out that $20,000 assembled car will cost at least $50,000 as parts.
Reply to
Jon Elson
I think its the paint. Just try buying a part with nice new green paint on it. You pay through the nose. That part out back with old paint on it isn't worth near as much.
Blue paint is even worse, cause you have to wait a week to get the wrong part. I've got four Ford tractors. I can't remember how many times I've been waiting on parts for two units and had to rob from one to get the other back in the field.
Reply to
Karl Townsend
A fair point. However, in the case of a drill press (an example I happen to be most familiar with) a cost of only three parts (2 step pulleys and a 1/4HP motor) exceeds the cost of the whole unit *new*. All the other parts are a bonus. Buying it in an auction nearly new for much less would just be an icing on the cake.
The other issue is availability: At this time I am not aware of any supplier which carries step pulleys in Canada, let alone locally. An EBay search threw up precisely 5 entries and not all of these were pulleys and some of the pulleys were highly dubious.
Making parts fit the design is just not realistic. I have so far found only one shop that carries *any* kind of pulley locally or in the next town. If your design does not fit them, tough luck. Thus a barnful of junk and genesis of a project on the basis on what is available seems the way to go.
There is not question that parts are more accessible in the USA, however shipping costs can double or triple the purchase price.
I am really talking about step pulleys to illustrate a point. I am not married to them as a solution for this particular problem. However, they are the most available item here. Gears of any shape are rare as hen's teeth and more expensive.
I had always thought people who cast things out of melted beer cans in their back yard as mildly weird enthusiasts. I am not laughing any more :-)
Reply to
Michael Koblic
On Fri, 26 Sep 2008 13:11:11 -0500, the infamous Jon Elson scrawled the following:
I believe it's over $100k now, Jon.
-- The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man. -- George Bernard Shaw
Reply to
Larry Jaques
Hey Michael,
I haven't watched this thread at all, but I did read the above.
White metal step pulleys are available lots of places. Canadian Tire, TSC, any good motor or bearing place. The ones at CTC may well be only 3 or 4 step, but they are there.
Heavier ones, such as Brownings, are available at any good farm or automotive place too.
Take care.
Brian Lawson, Bothwell, Ontario.
Reply to
Brian Lawson
Canadian Tire, being my second home, is where I looked first :-) Admittedly in their on-line catalog but believe me, here it is preferable to asking actual someone in the shop! Nothing.
I have never heard of TSC but looked them up. Ontario only?
However, as we speak I did find a second shop in town which is supposed to carry pulleys, including step jobs.
Still, my original point stands: From economic standpoint I would have done better to buy a $100 new drill press for the parts than buying them individually (the pulleys alone are $22.99 each).
As a side comment, one problem locating parts in Canada (certainly in BC) is that Canadian companies tend to have web sites considerably inferior to their US counterparts. House of Tools is pretty good. Lordco, OTOH, sucks. Many are in-between, e.g. having flyer and no list of products, no price lists etc. Some have good search engines (HoT) others not (Canadian Home Depot). Compare with something as slick as McMaster-Carr...
In a small community one depends on on-line information more and more. Phoning around tends to produce results that are variable at best.
Note to self: Must stop ranting!
Reply to
Michael Koblic
If you had a wood lathe you could make pulleys from glued wood bolted between aluminum sheets. The larger driven pulley doesn't really need a vee groove, for example my lathe has a vee pulley on the motor and a flat one on the countershaft.
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If you had a wood lathe you wouldn't need to because you could polish your disks on it. The kind to look for has a face plate mount on the left end of the spindle for turning large bowls.
A rotary sander or buffer will turn the work piece all by itself, you don't need to drive it separately, just allow it to rotate. You control the speed by the angle of contact.
When I ground the flat for the blade on the motorcycle tire for my sawmill I found that it made a good rotary table. It already has an axle with good bearings and a brake disk you could extend with plywood, the spinning tread isn't particularly dangerous although the spokes can be, and it has enough inertia that is doesn't speed up too quickly if the grinder runs parallel to the rim. The bike had been in a crash that bent the forks but didn't damage the wheel very much.
Jim Wilkins
Reply to
Jim Wilkins
Depending on your packaging constraints you could look at using a poly V belt drive with a one stage reduction. Have a look at a modern washing machine. I have used a poly V drive for a flat lap with about a 5:1 reduction and machined the motor pulley myself, the driven pulley being a VW Golf (still Rabbit in the US?) rear drum which provided the bearings and stubaxle to support the assembly with the lap plate being mounted on top of the drum. The OD of the drum was machined as standard and one benefit of poly V belts is that with reduction of over 3:1 IIRC you don't need the larger pulley to have Vs, it can be a plain surface. Poly V pulleys with taper lock bushes are readily available, at least in the UK, if you can machine your own.
Reply to
David Billington
----- Original Message ----- From: "Jim Wilkins" Newsgroups: rec.crafts.metalworking Sent: Saturday, September 27, 2008 5:41 AM Subject: Re: Economics of transmission
Do I understand you right? You are sanding/polishing as you driving the object in one operation? I wonder if that would clean up the edges, too. I got a 3-jaw chuck which I could get to spin on something while keeping the work in contact with a stationary disk sander. Now that would be brilliant!
Otherwise I can see how polishing could be done at 700 rpm but I was not sure about ruing up the edges - I thought that would have to be done somewhere around 60 rpm.
Right. You mentioned that before and I had some trouble getting my mind around it :-) I am still keeping that option open. I am looking at some woodlathes. The Canadian Tire has one for $167, but all the reviews suggest it is a POS.
However all of that is on hold as an opportunity has presented itself today to look at a real lathe (see my other today's post - what to look for before parting with cash!)
Michael Koblic, Campbell River, BC
Reply to
Michael Koblic
I was cleaning up the edge, trying to cut a flat wider than the bandsaw blade in the unworn tread of the front tire. The grinder was cutting crosswise at perhaps a 20 to 30 degree angle. When it cut straight across the wheel slowed and stopped, when it ran circumferentially the wheel sped up gradually to 80 MPH. It would be difficult to true up a disk that was out of round with a hand-held tool this way unless there was a tool rest, which the bandsaw frame provided.
A lathe like that should let you make a large polishing turntable pretty easily. According to my CAD drawing of water pipe, 3/4" pipe is 1.050 OD. You could turn a piece down to 1.00" to take trailer wheel bearings, screw on a floor flange and some plywood, and have your turntable. Pillow block bearings would be easier to mount if you can find some.
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I need to get busy on my lathe now. I bought a 1 ton I-beam trolley from HF and discovered that its wheels won't fit into 3" channel iron, so I need to turn them down a little.
Jim Wilkins
Reply to
Jim Wilkins

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