Member postings for JasonB

These people were EMSi you could e-mail them and ask

For the benefit of DC31K and anyone else who can't work out what is needed here is a section through the cylinder cover, it's the domed cream coloured surface that needs to be machined

If you draw a section through the cylinder end cover and then draw a line to follow the profile set away by the radius of the tool's tip you can then pick co-ordinates along that line.

For a relatively flat dome like you need the cross slide can be moved a convinient amount each time say 0.020" or 0.030" so draw a series of lines at your chosen spacing and then measure offsets for each one. I have taken the point of contact in the ctr to be 0,0 and you can see the further I bring the tool away from ctr with the cross slide the deeper each plunge cut is. eg at 6.5mm from the middle I'm plunging in 0.491mm.

You then just blend in the high spots to give you this

It works with any shape such as this decorative column capital

Edited By JasonB on 27/09/2021 19:18:58

I tend to rough them out with combined hand twiddling of the cross and top slide handwheels to get a shape that looks pleasing to the eye and then finish with a small handheld scraper. If you want them both identical then work out some co-ordinates in CAD and use those with a small round nosed tool then blend by hand

The metric drawings I have show it as 12.5mm and I assume the original imperial was 1/2"

Edited By JasonB on 26/09/2021 14:53:52

Look at the second photo the slot is much wider than the other as either the cutter has been wobbling about or more likely gone in beyond the parallel flute length and started cutting where it tapers out to the shank diameter so will be a tapered slot and need to be remachined.

Are you going to run on steam or air and if so will the engine just run for display or will you want it to work.

In most cases filling with JBWeld should do but if working hard at high pressure then a Sleeve may be the better option and that can be slipped in with Loctite 648

You will have to either remachine the inlet slot which now looks like it is too wide compared to the good one and may have a job getting a crisp edge to the JBW in which case machining out the whole valve chest deeper and inserting a plate would be the best cure

Also what's going on with the exhaust slot, that looks to be over length for part of it's depth so you may need to widen the valve to get a good seal at the edges or see plate mentioned above

Where did that one come from?

If you want to convert between DP and mod the calculation is DP = 25.4/MOD

So if you had a 2Mod gear and wanted to know the equivalent DP you would use DP = 25.4 / 2 = 12.7DP as confirmed buy my usual go to conversion chart here

I did the water pocket on my Fowler by turning the shape, cutting in half and then soldering on a flat plate, gave the other half to another builder to save waste

The other method would be to make it up from several bits, the lower part cut from solid, some thick wall tube for the larger diameter and possibly the bead as well or a separate bead and a flat plate to solder onto the side.

Edited By JasonB on 25/09/2021 16:09:05

The needle valve won't alter pressure, just volume of air or steam for that matter that can get to the engien. On an unloaded engine i's all about the volume of air getting into the cylinder.

My compressor reg will go right down to zero bar but most of the small double acting engines I will set it to 0.2BAR (3psi), single acting usually need a bit more about 0.6BAR (10psi)

Another example in this video compressor remains set at 10psi, for the first 90secs I'm making use of the reverser to alter the cut off so speed changes relative to how much air can flow into the cylinder. After that I'm using the flow valve to get speed right down to a tick over or going like mad. Too high a pressure on an oscillator will lift the cylinder off the port face or need excessive spring tension and therefore friction to keep it on the face.

Edited By JasonB on 25/09/2021 13:05:25

I use the compressor regulator to set the pressure that I want ( yes I'm a low psi man)

The speed is then regulated buy a second flow valve which I find far more controllable than a ball valve. I use several of the the push fit ones of various sizes screwed into a manifold but you could just use a single one in the airline.

I don't think it's that critical unless you have a massively different angle seating to the holder, main thing is to make sure nothing rubs particularly as the swung diameter reduces much like you do with a boring bar.

I used various lathe tools, round button tools, commercial ground flycutter bits and many home ground ones and all work

But would stepping out with dividers not have the same problem as measuring with callipers in that you are stepping out a cord not an arc?

Jo on Modelenginemaker forum bought a set from Adrain at Engineer's Emporium a couple of years back who had bought a few sets said to be cast from Ronnie's patterns and I think he also got the patterns. She said she would do him a set of drawings, though nothing has materialised and she was just going to base them on an RLE .

It's not that good a representation of the Bamford, better described as "inspired by" rather than a scale model. There was a two page article in Stationary Engine mag which is also reproduced in their book on models but no sizes given

Yes larger nut makes a simple spacer. I tend to thread my own studs, 3/32" rod will be fine for 7BA

Already answered by Andrew yesterday:

" In theory it should be able to cut small numbers of teeth as well. The undercut arises automatically. In some of the 1930s books I've got on gear cutting there are formulae for calculating whether a hob will undercut or not, even when not needed"

This is how the Sunderland machines do it and what is suggested for the CNC method being discussed except a round rack form cutter will be used instead of a flat shaper type cutter as it is easier for a hobby user to make.

Not sure what you are trying to do with your head on it's side and a large dia cutter? Can't you tilt the work

Usually just called X-axis and Y-axis.

Neither Neil's basic method or the CNC method would need any movement in Y except the initial setting of the "whole depth".

Edited By JasonB on 21/09/2021 19:44:45

Try M-machine, they will likely cut to size.

I think You need to be on the meds Brian if you are not all ready.

SOD was talking about Neil's and my cutters which are rack form and rotate and the gear blank is fixed to an arbor that is indexed.

Also never seen a mill with a cross slide maybe you don't know your mill from your lathe

Yes I have seen ACME taps and wondered how long it would take you to twig that an ACME thread form with it's 29degree angles might be worth trying as it could possibly give the 14.5pa of old gears such as the ones found on a Myford and the pitch is reasonably coarse too. Biggest problem is they are rather long, not that cheap and mostly straight fluted.

My simple vice stop with drawings is here, will clamp onto quite a small jaw projection and also allows quite thin stock to be held when it's in use.