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Leon B MO 
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Joined: 12 Sep 2009
Location: Old Monroe, Mo
Points: 2179
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 Topic: pto rpm ratio
Posted: 06 Dec 2015 at 7:27pm |
I'm converting an old Jaeger portable air compressor to pto. The old Continental motor turned 800 rpm's at full throttle. I'm going to run a jack shaft from the compressor to a pto driven shaft. Assuming my WD pto turns 540, am I figuring right that I need to increase the driven shaft by 1.48. If I use a 21 tooth gear on the drive shaft and a 15 tooth gear on the driven, will I get about 800 rpms at the compressor? Just making sure my math figures out about right. Thanks
Leon B
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Uncle always said "Fill the back of the shovel and the front will take care of itself".
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DiyDave
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Joined: 11 Sep 2009
Location: Gambrills, MD
Points: 53487
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Posted: 06 Dec 2015 at 8:09pm |
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Search gear rpm calculator on google. Scads of them out there. Just plug in all the #'s you have, and out pops the unknown item...
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DrAllis
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Joined: 12 Sep 2009
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Posted: 06 Dec 2015 at 8:28pm |
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A WD should run right at 1700 RPM wide open throttle, which yields 650 RPM at the PTO. I'd go with 17 and 21 and run the tractor wide open. Unless you have a tach on the tractor, how do you know where 1400 RPM is ??
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Leon B MO
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Joined: 12 Sep 2009
Location: Old Monroe, Mo
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Posted: 06 Dec 2015 at 8:33pm |
Thanks Dave, that site it helpfull. Looks like I need a 22 drive and a 15 driven to get 792 rpm's with a 540 pto. Leon
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Uncle always said "Fill the back of the shovel and the front will take care of itself".
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wayneIA
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Joined: 17 Oct 2009
Location: Waverly, IA
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Posted: 06 Dec 2015 at 8:38pm |
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May want to double check the continental motor rpm, 800 is pretty slow. I don't know if maybe you had a typo, and meant 1800 rpm on the engine? I have an old Leroi that is supposed to turn 1400.
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Leon B MO
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Location: Old Monroe, Mo
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Posted: 06 Dec 2015 at 9:09pm |
This old motor has given me trouble for quite some time, very tempermental. The last time I had it running, I put an rpm gauge on it, the govenor was air pressure controlled. If I get "in the neighborhood" of 800 rpm's, it will be fine. If the CA will run it, that's what will be on it, if not I know the UC will make her talk, don't know the hp requirements of the compressor. It will be easier to hook up a pto shaft than try to get a very stubborn motor running. After I get everything up and running, I'll put the rpm tester on it and find the proper throttle setting. Leon B
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Uncle always said "Fill the back of the shovel and the front will take care of itself".
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Gerald J.
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Joined: 12 Sep 2009
Location: Hamilton Co, IA
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Posted: 06 Dec 2015 at 9:54pm |
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The compressor will give the same air pressure at most any shaft speed, though at very low shaft speed the piston ring leakage will lower the available pressure. What's affected by shaft speed is the volume. If it does 15 cfm at 800, it will do 10 cfm and 540. I'd run it at 540 rather than create the gear box to turn it faster. And if I figured I had to turn it faster I would figure a belt or chain drive would be easier to build than a gear box, but I suspect it will do all your work just fine at 540 RPM. At the worst case you might have to be a little bit more patient when using it, at the same time the time you may have to wait in a year of use will probably be less than the time it will take to build and install a gear box.
Gerald J.
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Dan73
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Joined: 04 Jun 2015
Location: United States
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Posted: 07 Dec 2015 at 5:10am |
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Gerald J I was thinking along the same lines. I would just add that running the compressor at a lower speed will be alot easier on the mechanical components.
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wayneIA
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Joined: 17 Oct 2009
Location: Waverly, IA
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Posted: 07 Dec 2015 at 5:47am |
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On the HP requirement, my compressor is supposed to be 125 cfm, the engine is essentially a WD45 gas with flat top pistons. Until the oil gets warmed up really good, it'll pull the engine down and I have to manually unload it to allow the compressor to run and warm the oil. Not knowing how many cfm yours is, I'll bet if the CA can pull it, you won't have any issues with carbon build up. It'll depend too on how fast you run it in the end.
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marion
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Posted: 07 Dec 2015 at 8:01am |
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I built one few years back, had 6 cylinder frick compressor and adapter plate on flywheel ran by pto shaft hooked to a 45, at 500rpm ended up being 80 cfm, ran small tip on blaster, finally graduated to self contained 185, believe it or not couldn't give away pto air compressor and sent it to china
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bradley6874
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Joined: 05 Sep 2010
Location: salisbury md
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Posted: 07 Dec 2015 at 8:28am |
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How big was the old motor why run the wd wide open if you have enough power at say 1/3 throttle gear it fo that save fuel and where on the old girl
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You can wash the dirt off the body but you can’t wash the farmer out of the heart and soul
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Butch(OH)
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Joined: 11 Sep 2009
Location: Lucerne Ohio
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Posted: 07 Dec 2015 at 8:29am |
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I have an old Jaeger also and the old Continental runs like a top. Not sure what CFM it is but guessing around 100, its a 3 cylinder compressor. It takes everything the Continental has to top the receiver off at 100 PSI, matter of fact it wont pull it with cold oil. I am wondering if a WD will have enough HP to run it?
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Stan R
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Joined: 03 Dec 2009
Location: MA
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Posted: 07 Dec 2015 at 12:06pm |
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I'm curious: what are you going to use the compressor for?
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