The Shop > Tools
Shaper motor suggestions?
PerryRT:
--- Quote from: vtsteam on June 25, 2015, 07:24:48 PM ---If you're considering some of the common treadmill DC motors for sale on Ebay, be aware that they are often rated for that nameplate "horsepower" at 6000 RPM, or so, and often at an odd voltage, too. So you'll get considerably less usable power out of it, especially if you are using the speed controller to not only adjust speed but provide some of the reduction, rather than one or more pulley steps and/or a jack shaft. The actual power available at low RPM on the motor will be only a small fraction of the nameplate rated power.
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Yeah - I researched that idea for repowering my lathe (different project) and hadn't considered one here because of the RPM that you mentioned.
What I was thinking about here was a 90 or 130 VDC motor from eBay around 1/2 to 3/4 HP and a speed controller to match, but as I said, I still have much to learn.
--- Quote ---btw, it's not so easy to overpower anything driven strictly by the usual single vee belt reduction after replacing a jackshaft with a speed controlled DC motor. It's possible to suffer more from belt slip problems. Depending on tension and puley sizes, of course, but a vee belt can serve as a clutch to prevent overpowering. Everything is dependent on specifics -- this is all generalization without them.
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I agree there. I just want to be safe, though.
PerryRT:
--- Quote from: RussellT on June 26, 2015, 04:28:10 AM ---Does it still have the original stepped pulley on the side of the shaper? That gives some scope for adjustment of speed and torque.
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Yes, the stepped "input" pulley on the side of the machine is there. I suspect that this unit was driven like I plan to (with a direct drive) prior to this. Unfortunately, I bought it from a dealer and don't really have a history on it.
--- Quote ---You'd need the smallest pulley you can get for the motor (normally limited by the belt). You could get more reduction if you changed it to a polyvee belt drive as you could get a smaller pulley on the motor (polyvees go in smaller radii).
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You know, I actually haven't checked what it uses yet. I was kinda assuming a standard 3L or maybe an A because of the age, but that's worth checking out.
--- Quote ---Is there room on the side of the shaper to fit a larger pulley there?
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Possibly.
--- Quote --- How about some phots of the actual machine?
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Will be glad to provide them, but will have to wait until Sunday, I'm afraid - out of town with the wife for the weekend. Shhhh....everybody be quiet, she's noticed I'm distracted! :Doh:
PerryRT:
--- Quote from: RussellT on June 26, 2015, 03:10:14 PM ---There seem to be some other variables other than the basic 3:1 reduction to the countershaft.
The stepped pulleys probably provide 2:1 1:1 and 1:2 and you need to think about when you would have need those ratios. I suspect (and I've never operated a shaper so it may be rubbish) that it will depend on the job you are doing. I think there is a further effective reduction depending on the length of the stroke - so a short stroke job will need less torque and can run faster than a long stroke job.
I think it'll probably work with direct drive - but if you can I'd still try and build in as much mechanical advantage as I could.
Russell
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The stroke length is governed by a scotch yoke set-up downstream, but that's a good point....for the same RPM at the input pulley, a longer stroke would seem to require more torque , right?
As for the stepped input pulley, I was honestly considering it as solely a way to set max possible speed and then leave the rest of the speed variance to the motor controller. In other words my plan is to set up the vbelt once and never touch it thereafter.
The reference books I'm reading seem to mainly talk about speeds/feeds in terms of strokes per minute rather than RPM, but due to the scotch yoke, on this shaper those are the same (ok , proportional) , 1 rev = 1 stroke. The total possible stroke defines the shaper, incidentally - in this case, a little over 7 inches.
We'll see. I have to admit, that's one of the reasons I still like this hobby - there's always more to learn.
PerryRT:
I spent some time today after we got back - last weekend I built a stand. It's a lightweight wooden job, but should serve (and if it doesn't, I've got another workbench.) Anyway, I didn't have much time, but I wanted to get the shaper up on the stand and figure out mounting/screws etc.
General shot from the left (non-pulley side) (Attachment 1)
A closer shot from the right side looking at the input pulley and table feed mechanism (Attachment 2)
and finally a shot of the end-on view of the input pulley (Attachment 3)
The rough dimensions of the pulley OD are 4.5", 3.5", 2.5" and 1" with a slightly over 0.5" pulley width (so I'm figuring an "A" series belt will work.)
One other data point I found - according to the original manual, the shaper was able to provide 40-180 strokes per minute. Again, I figure that the relationship between RPM and strokes per minute is consistent. However, it's NOT 1:1 as I thought earlier. Turning the unit by hand, it's about 6:1 (one full cycle of the ram for 6 revolutions of the pulley.) So that means that they were expecting no more than 1100 RPM at the input pulley, more or less.
More later - gotta do some math....
Lew_Merrick_PE:
>> Stop and think about this. The original equipment had a 1/3 HP motor running through a 3:1 reducer. The base equation is: Torque (in lb-ft) = HP X RPM/5252.
Brain Fart Alert! The base equation is: HP = Torque X RPM/5252 which gives: Torque (lb-ft) = HP X 5252/RPM. [And "5252" is "short" for 550 X 60/2pi which is more accurately stated as 5252.1131 just in case anybody's interested.]
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