Here is a list of all the postings Robert Dodds has made in our forums. Click on a thread name to jump to the thread.
|Thread: That Strange Calculator Again|
Next stop should be The Arithmeum,. Bonn University. It has a museum of mechanical calculators, lots of them are circular and there are 10000 exhibits to check out. Some of the detail is in German so you may need some translation before calculation.
Worth a click on this site to see it in operation.
Note the right thumb on the black bar to stop the inner ring rotating until required
I've just looked back at Grindstone Cowboys earlier link to reddit. Trawling down to KarenEiffel's response led me to an illustrated book of Rechnenmaschinen. Look a bit familiar?
I'm a long way from understanding this device but I do wonder whether it might have had some pins or similar that went into the small holes of the inner disc and circle and registered them in set positions for some setting purpose.
Segment 6 3/8 2/5 -6(0.020833) = 0.375
5/12 -2(0.020833) = 0.375
Has this got any significance?
|Thread: Half nut skipping still|
Will your 6mm rod pass through the vertical slots in the apron or are they designed for 3/16" rod.in which case you will need to make them look like cheese head screws.
Reference the symmetry I wrote about, check the two dimensions indicated on your edited photo and see if they are near equal. They will determine which of your half nuts moves most when you rotate the "banjo"
In making those 6mm pins do make sure that the 3/16" thread is concentric as possible with the 6mm O/D.
As a last resort to avoid shims on the Apron the 6mm pins could intentionally be made eccentric to the threaded portion and thereby vary the engagement position of the half nuts, but that's not for the faint hearted.
Get your slots uniform in size and round particularly at the nut closed position. then produce two pins of a diameter to suit your slot size less 0.002" to 0.005"and get the thread as concentric as possible . I would remove shims at initial tryout as I doubt that it left the factory with shims. After all they cost less than £20 in the thirties so didn't get much individual attention.
Regards Bob D
Edited By Robert Dodds on 27/11/2021 21:56:25
I've just had a closer look at my Zyto and taken a couple of shots of it.
When i look at your first photo there appears to be a substantial clearance between the scroll slots and your pins,( wobbly threads on another query) On my machine the pins are a reasonably close fit to the slots and my take is that your slots are badly worn or maybe modified. It is the proper fit of these pins in the slots that gives you the lock in of the half nuts. You need a, uniform width slots and b, good fitting pins in the whole length of the slots to keep the half nuts engaged.
Not to be recommended but strictly speaking a single thread on your top half nut should be sufficient to produce a good screw thread on your workpiece, at least for a limited time!
I notice that you do not show a large washer over the lever assembly. For what its worth mine has a full diameter cover washer which has a tapped hole in the centre. The pivot shaft has a screwed extension onto which the washer screws and then it is locked in position with a domed nut, which is then used to control the fit of the lever assembly . Too tight and you can't turn the lever.
Depending on your skill level I would be filing out the slots to a suitable drill shank al the way along the slots, then making two oversize pins to suit the slots and having another go.
Regards Bob D
Edited By Robert Dodds on 27/11/2021 15:52:44
|Thread: Axminster Drill Clamp|
Very useful but do fit a heavy gauge flat washer next to the eye-nut under the table. Depending on the rib configuration on the underside of the table a hex nut may be more versatile than the eye-nut.
|Thread: Peter Gilliland|
Once upon a time there was trader selling Atlas spares. I got a pair of half nuts and some change gears from him I recall but I can't remember any contact details. Anybody had contact with him in the recent past?
|Thread: What is it|
A hint about the size might help. I have some reservations about valve guide de-coking, it's mainly the stem immediately under the valve head that gathers coke.
|Thread: Strange WW1 Chuck - 1MT|
I've dug out a similar design of chuck.
|Thread: Ideas on how to make up a G-Clamp Swivel Foot|
Regards Bob D
|Thread: Twinner Multi-Jigset (what is this tool for?)|
From the E bay photos they look like early forerunners of today's toggle clamps.
|Thread: Silver solder? ....... or what?|
My guess is one of the several varieties of SIF bronze. Father in Law used to use it for repairing cracked Cast Iron with an oxy-acetylene torch . It's Silicon Bronze with a dash of of silver and tin in it There are lots of suppliers still around, . give one a call to check the colour coding.
Regards Bob D
|Thread: Pulley size help required.|
Your photos show your Atlas to be a later model than mine and I'm glad you can see a solution.
Regards Bob D
Edited By Robert Dodds on 18/06/2021 12:24:06
Edited By Robert Dodds on 18/06/2021 12:49:20
Edited By Robert Dodds on 18/06/2021 12:50:33
In my photo is the belt set to high or low speed ? With the second cone set to top speed it does about 600rpm with a 1400 rpm motor.
I've got an Atlas with 2 speed primary drive. picture attached. Daft question but "do you have the motor pulley as my configuration? small motor pulley to large driven pulley, If not, try reversing the motor pulley on its shaft to look more like mine That works fine for me.
Hope this helps
|Thread: A bit more upcycling.|
Like it, A lot.
|Thread: Does anyone know what this is for?|
I think I can see two rollers, one at the handle side and another at the opposite side. Both have semi circular profiles and in one picture there may be a third roller which looks to be horizontally mounted in the same plane as the other two. I ask if this could indicate some form of wire bead folder similar to that which was used in auto construction in the 1930s.
One maker has a video of making a bead rolled edge on a vintage Ford body panel that's well worth watching.
I can't explain the purpose of the outboard rollers but I think the primary tooling is hiding inside the head somewhere and that the hand lever is used to relieve pressure (from the big spring underneath) whist loading the part to start whatever.
Hope my musing makes sense to others
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