It'll take me several hours to get my head around how it works, lol...
- Thread starter Pete.
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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
Johnnybravo
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Bloke is a dreamer. Had that box of hobs I looked at fitted, they would have been £250 for the box. About 10 in the box, most new.
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…
mtt.tr
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You are probably right, total target fixation.
Now we would say they were on the spectrum.
Johnnybravo
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You look at some of these machines and think wow, somebody designed that. What most people don’t factor in, is that in most instances it started as a much simpler machine and each new design got steadily more involved.So gradual progression and working out the bugs as you go along. Keep what works and improve on the weak parts. Before you know it you have a very complex machine.
mtt.tr
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And now we have servos and encoders.
Seadog
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And all done on a drawing board!
Pete.
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Tonight I stripped off the gear train plate that holds the gear sets for the feeds and differential gears. I wasn't going to remove this but after spending quite a considerable time with light oil and penetrating fluid I just couldn't get the feed release lever moving without feeling horribly gummy. In the end, I took it all off, stripped it down and now it works with a light touch and I'm glad I did because most of the gumminess was due to old oil in and on an internal sleeve which held the slidiging dog gear and no amount of lubing or trying to force oil into the oil nipple was going to clear it out properly.
Here is the plate on the outside with the banjos removed. The drive for the feeds comes in via the bottom middle drive spindle which has a spiral gear that engages with a 5 start worm on the silver shaft behind the plate. This spindle has gears which mesh with the shaft on the right (the one with the square drive) which then has a bevel gear on the back that drives a vertical shaft for the downfeed for hobbing gears and a horizontal shaft for infeed for hobbing wormwheels. There is also a neat automatic knock-off system that trips out the feed in either direction using sliding stops which you can see in the pic.
Here's the feed shaft with the 5 start worm wheel at the bottom of the pic. Also seen are the two bevel gears that provide downfeed and infeed power.
The internal gearing. Showing the spiral input gear and the sliding dog that engages the bevel gear with the feeds gearbox.Also see the three gears which carry power to the differential banjo. All the time that the machine is runnng, the feeds gearbox and differential gearbox are also turning all together.
It's important to note that because the differential gearbox is driven from the feeds gearbox, at a 1:1 ratio you can change the feedrate for optimum cutting without affecting the differential ratio.
Here is the plate on the outside with the banjos removed. The drive for the feeds comes in via the bottom middle drive spindle which has a spiral gear that engages with a 5 start worm on the silver shaft behind the plate. This spindle has gears which mesh with the shaft on the right (the one with the square drive) which then has a bevel gear on the back that drives a vertical shaft for the downfeed for hobbing gears and a horizontal shaft for infeed for hobbing wormwheels. There is also a neat automatic knock-off system that trips out the feed in either direction using sliding stops which you can see in the pic.
Here's the feed shaft with the 5 start worm wheel at the bottom of the pic. Also seen are the two bevel gears that provide downfeed and infeed power.
The internal gearing. Showing the spiral input gear and the sliding dog that engages the bevel gear with the feeds gearbox.Also see the three gears which carry power to the differential banjo. All the time that the machine is runnng, the feeds gearbox and differential gearbox are also turning all together.
It's important to note that because the differential gearbox is driven from the feeds gearbox, at a 1:1 ratio you can change the feedrate for optimum cutting without affecting the differential ratio.
julianthegypsy
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With log tables and slide rules!
Agroshield
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Because everything is geared and thus every gear has an integer number of teeth*, all the 'mechanical maths' is strictly ratios of integers (fractions). Log tables are not so helpful there. What is needed is a very good grasp of the maths of continued fractions (where you can find a ratio of two integers that are arbitrarily close to any number you like).
*(none cut by me, as a few I have tried to make have had 37 1/2 teeth)
Johnnybravo
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Schoolboy error….Everyone knows only imperial gears can have 37 and six twelfty third teeth. I bet you tried to cut that as a module gear,not DP….
Pete.
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For the indexing of teeth that is true but for the differential calculations it absolutely does (did before the invent of calculators) require log table calculations and there's an example in the manual in fact. The four-gear train used to set the helical gear compensation is rarely perfect, you're expected to work to at least 5 decimal places and choose four gears for your train that produces the closest possible helix.
There are books which contain hundreds of pages of four-gear ratios (A/B x C/D) and I need to get my hands on one of them so if anyone has the Pfauter/Gleason book I will pay for a copy of it). The magic number is called the machine constant which is (thankfully) given in the supplied manual and I'm glad it is because without that one single number I would not be able to do the calculations at all. I would have to find some way of discovering the constant by measuring and I shouldn't like to have to attempt that.
julianthegypsy
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I remember in college a farmer brought a huge pivot shaft for a big reversible plough, snapped in half. Usual rules, a nice donation to the college "scrap" fund in return for a shiny new one. The metallurgy lab sorted out what the steel was, and why it failed, then metrology started measuring. Then there was a very large tapered section. Out came the calculators, except for one old lecturer, who pulled out a set of ten figure log tables. He had it nailed in no time and no one else came close to his accuracy.
The shaft was then machined and ground to size and is probably the only part of that plough still serviceable forty five years later. Our college was something else in those days!
The shaft was then machined and ground to size and is probably the only part of that plough still serviceable forty five years later. Our college was something else in those days!
Agroshield
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I think this is some attempt to do that:
Find Differential Constant - Articles of Interest to Gear Manufacturers
www.meshingwithgears.us
It is a good site to skim through as there is some obscure stuff there.
Do you know the title of the Pfauter/Gleeson book?
