Pete.
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Johnny you the man, I found that video and in it is a perfect schematic of my machine's geartrain (and a description of how the differential works).
- Thread starter Pete.
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Johnny you the man, I found that video and in it is a perfect schematic of my machine's geartrain (and a description of how the differential works).
Martin Hocking
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So the helix is created by a gain or loss per rotation in the index feed?
Is there a link to the video? What is purpose of the differential?
Can’t the extra index feed be recreated by a slightly incorrect index train for the regular spur type?
Is there a link to the video? What is purpose of the differential?
Can’t the extra index feed be recreated by a slightly incorrect index train for the regular spur type?
paradipiro
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The differential adds an option to make bevel gears. If the differential is not in mesh, then the result is a helical gear. If the differential is engaged, (the table rotation is slowed down or speeded up refer to the reference, the helical gears teeth can be left or right angled. The differential's gearsets and resulting angles are in a big-big table in the manual.
paradipiro
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The teeth width is measured, then corrected by the depth of cut. First, you make a heavy cut around 75-80% of the final tooldepth, then measure the tooth width (W(k) in EU), then make a final pass accorduing to this dimension. I only know the metric measurements. Eg if the desired tooth width is off by 1mm or so, then you make a cut with this off-dimension with a correcting factor (~~1,43? I dont rememeber). The factor and all this method is mentioned in the manual. I only worked with a Lambert No. 68 hobber.
But the tooth width tapers along it's length? so it would need to be cut 3 times?
Hmm, maybe bevel gears need a special machine, with shafts at adjustable angles, maybe shaper territory?
The theory for doing it in a mill with dividing head I can understand, but it would be easy to c*ck up...
paradipiro
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Yea.. it's not bevel gears, it's called helical gears.. I f*cked up with the correct word..
Martin Hocking
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Excellent recommendation mr bravo. I’ve just watched this video:
Does a very good job of explaining a little of the maths behind it. I feel a bit more with it. Assuming anything he just said is actually correct!
I enjoyed this one to mr mutly. I am rather jealous of people who can communicate concisely.
I still don’t quite understand whether it’s just not possible to calculate an index gear train with the correct ‘drift’ in its indexing so you have to have the differential or whether it’s simply the case that you’d need 100’s of different change gears to be of any practical use on a machine.
In any event mr pfauter gets a round of applause from me…
It'll take me several hours to get my head around how it works, lol...
God mode restorations
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The machine is for sure a work of art. Will pop over pete one weekend pete when ya got it sorted
Agroshield
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Something working on a very similar principle was the mechanical torpedo computer. There are YT videos on its operation including differentials and other clever mechanical computing stuff (they did a lot with cams). Somewhere or other the manuals/parts diagrams have been scanned.
Pete.
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Few more jobs done. First the giant 1hp motor was 415v only, so that came out and was replaced by a NOS 1.1KW unit I got from a kind member here which has star-delta links. Next will be fitting of a VFD to run it.
I also cleaned up the index gearing banjos and re-fitted the main input gears. The gears fitted are 30:30 so give no ratio change. There's a 20:40 set also which provide for 1:2 and 2:1 ratios for very low and very high tooth count gears.
The top gear here is reversible. When fitted as above it locks the differential for cutting spur gears. Whan flipped over so the drive dogs are not engaged, the worm drive for the differential is engaged and you can cut helical gears.
These I did over the weekend along with a bunch of other minor jobs like freeing up the infeed worm drive drop-out rod and general oiling and servicing.
Tonight I decided to make a missing part. The infeed handwheel has a dial behind it that you use to set the depth of cut. The dial is settable by a lock ring but for some reason the keyed washer that should be behind the lock ring was missing and replaced by a random over-sized screw ring. It is very important that setting this wheel is both easy and reliable because when you touch the hob to the job you need to be able to zero the dial and lock it with a very light touch.
Here's the Bronze feedscrew that holds it all.
I turned the ring from 303 stainless which is lovely to machine and won'trust or tarnish, then broached a keyway 1/8" in it. The keyway looks drunk in the pic but it's not.
Then I gound a 1/8" wide by .100" tall key in some random old keystock
I cut it off and it was a nice snug fit in the slot. Only about 30 thou sticking out which is perfect for the shallow keyway in the shaft. It doesn't need fixing because it cannot slide out of either end once it's all assembled.
Here it is re-assembled with a slotted BSF grub screw that I was lucky to find in my pot of bits. A very satisfying couple of hours work.
I also cleaned up the index gearing banjos and re-fitted the main input gears. The gears fitted are 30:30 so give no ratio change. There's a 20:40 set also which provide for 1:2 and 2:1 ratios for very low and very high tooth count gears.
The top gear here is reversible. When fitted as above it locks the differential for cutting spur gears. Whan flipped over so the drive dogs are not engaged, the worm drive for the differential is engaged and you can cut helical gears.
These I did over the weekend along with a bunch of other minor jobs like freeing up the infeed worm drive drop-out rod and general oiling and servicing.
Tonight I decided to make a missing part. The infeed handwheel has a dial behind it that you use to set the depth of cut. The dial is settable by a lock ring but for some reason the keyed washer that should be behind the lock ring was missing and replaced by a random over-sized screw ring. It is very important that setting this wheel is both easy and reliable because when you touch the hob to the job you need to be able to zero the dial and lock it with a very light touch.
Here's the Bronze feedscrew that holds it all.
I turned the ring from 303 stainless which is lovely to machine and won'trust or tarnish, then broached a keyway 1/8" in it. The keyway looks drunk in the pic but it's not.
Then I gound a 1/8" wide by .100" tall key in some random old keystock
I cut it off and it was a nice snug fit in the slot. Only about 30 thou sticking out which is perfect for the shallow keyway in the shaft. It doesn't need fixing because it cannot slide out of either end once it's all assembled.
Here it is re-assembled with a slotted BSF grub screw that I was lucky to find in my pot of bits. A very satisfying couple of hours work.
Pete.
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There is. It's one thing to look at the machine and figure it out, another thing entirely to figure it out and design it.
A couple of people have said that this is a copy of one of the smaller Pfauter models. I was sceptical because looking at those models there are significant differences, but getting hold of the gearing schematic shows that the workings inside are virtually identical, the arrangement certainly is.
Martin Hocking
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In many ways it’s the things these people must have forgotten while consumed by these thoughts that fascinates me…
