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| Andrew_D:
I did exactly this type of mod to my 7x12. Spindle extension off the left hand side holds a 4-step pulley and still allows up to 5/8" shaft to pass through. That was tricky....left hand internal metric thread to cut so that it screws onto the spindle.... :bugeye: Another 4-step pulley on a jackshaft mounts on the rear of the lathe. This jackshaft is driven by a treadmill motor through a 1:5 reduction belt drive. The treadmill motor is powered via a DC-controller I found on EBay. Some type of obsolete industrial control. Took a bit of work to find out the specs and jumper settings for it, but the company was quite helpful. I don't have any pics, I'll see if I have time to take any later today..... I'm thinking of giving the old girl a cleaning up, but not sure how far to take it...tapered bearings? longer bed? Also the tailstock is very stiff. I think the tailstock spindle got bent, or the casting is buggered somehow. Was thinking of taking off the tailstock and carriage and making a small turret lathe...so many ideas, so little time and money.... Andrew |
| loply:
Andrew, how long was the spindle extension and are you confident that the drive force being exerted a few inches away from the spindle bearings isn't creating any unwanted imbalance? I'm concioua that any misalignment of spindle extension or pulley bore will result in a washing machine lathe :bugeye: Although it's overly complex I'm actually pondering a belt driven layshaft in the location of the original motor whereby two belts can be selected by means of a motorcycle gearbox type dog system, the reason being that I would end up with two gear levers (including the original one) in approximately the same place on the back of the headstock for a nice quick change system, and could have ratios with max speeds of 145, 380, 680, and 1000rpm... Exactly the kind of range I want! First just getting the head rebuilt and my DRO fitted though... |
| John Hill:
--- Quote from: Bogstandard on June 07, 2011, 08:38:06 AM ---Have a look at John Hills or Powder Keg's posts for example. THEY are what Modders was originally intended for --- End quote --- :med: :scratch: :lol: |
| Andrew_D:
--- Quote from: loply on June 07, 2011, 03:36:43 PM ---Andrew, how long was the spindle extension and are you confident that the drive force being exerted a few inches away from the spindle bearings isn't creating any unwanted imbalance? --- End quote --- Never thought too much about the extra side forces to tell the truth. ::) I had a look at the ol' girl today...it actually was a 3-step pulley. This gives 1:2, 1:1, 2:1 ratios (relative to the jackshaft). The jackshaft is 1/5 the motor speed. I took some pics, but am currently trying to put kids to bed, so will check back in a bit... Andrew |
| Andrew_D:
Here's some pics... The piece that screws on to the spindle is actually three pieces. The 3-step pulley, a piece of round tube/pipe, left-hand thread nut. I had to make a replica of the spindle thread first using one of the original nuts as a go/no-go gauge. (Before removing the gauge from the chuck, I marked where jaw #1 was...see why later.) Once I had the piece threaded, I made the nut and threaded it, using the go/no-go gauge as I cut the thread. I milled some slots in the nut to provide a means of tightening. (Similar to the original nuts actually.) This nut was then welded to a piece of thick-wall tubing. The go/no-go gauge was chucked back up thanks to my marks made before and the nut/welded tube was screwed on. A couple light facing and turning cuts to square things up. The center was then bored out to about 1" if I remember correctly. The nut was removed from the go/no-go gauge and the gauge removed from the chuck. A hole for a set screw was drilled and tapped in the side. Now the pulley was chucked up. In the end of the large pulley, it is recessed. (Cheap buggers couldn't leave THAT much aluminum behind!!!) The center was a hair over 1". I turned it down slightly until the welded nut slid on about 1/8". I then took the pulley & welded nut over to my horizontal press (big vise!) and slowly pressed the two together with some red loctite. The set screw was also added for extra holding power. Nothing special about the frame work holding the jackshaft. Some 2" x 1/8" wall tubing extended back from under the base. (I had made two lift blocks out of this tubing earlier to raise the lathe up off the bench, so this frame work simply replaced the headstock lift block.) The jackshaft bearings are mounted on some 6" x 3/8" plate, hinged at the bottom. A simple tensioner keeps the belt tight. The motor hangs off the top rear of the jackshaft plate. Another simple tightening bolt here too. The numbers, as mentioned earlier....the pulleys provide 1:5 from motor to jackshaft, then 1:2, 1:1, 2:1 to the spindle. The motor is 1.5 HP continuous duty @ 95 VDC, 2.5 HP treadmill duty @ 130 VDC, 18.5 Amps 6750 RPM. This gives the motor a range of 0-6750 RPM, the jackshaft is 0-1350 RPM, and the spindle is 0-675 RPM, 0-1350 RPM, 0-2700 RPM. The motor is run with a obsolete industrial control I found on EBay...much better than the original motor and controller!!!! Andrew |
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