Member postings for Iain Downs

Like the OP I bought a CMD10 from Machine Mart. In my case it was full price - clearly I lack bargaining skills!

I found myself going through gears like lollipops to start with and it was a while before I discovered you can adjust the mesh in the gearbox. Since then I've not had any gear failures.

I did do some of the twiddles (thrust bearings on the X and Y for example, attempting to scrape the ways and replacing / improving then jibs) but other than that it's served me well.

Unlike the OP I've managed to stall the motor (and blow the fuse) on more than one occasion - I'm just more brutal I guess. Despite that the machine has gamely carried on.

The little machine has tackled some surprisingly large jobs with more competence than its owner, including the build of most of a 50mm bore vertical mill.

I would, however, echo the general comments in this forum. Bigger is better. I upgraded to a somewhat bigger mill a couple of years ago and it was transformational. Even more so when I added DRO.

Iain

I like to look at the for sale section from time to time and I've noted that the widget on the home page which shows the latest for sale items seemed to get stuck a week or so back. It's not changed since then even though there are quite a few items added to the actual for sale page.

Just to let you know!

Iain

I've bought stuff from Cousins this week and had no problems - not a pro, just a bumbler.

Iain

I've become interested in tweezers due to starting to play with watches. Whilst you can pay a lot of money for tweezers, it seems like it is more important to 'dress' them. That is to use files / stones to tune the ends of the tweezers to be appropriately sharp and have the right profile.

The test (I was told by someone in this forum) was if you could pick up a hair from a sheet of glass with the tweezer.,

The set I have cost under 20 quid for 4 and after filing and dressing (and practice) they are of that quality.

I don't think you need to spend a lot.

Iain

Thanks for taking the time to have a look, Jason

If you mean what I think you mean, there are no cuts on the covers or bottom plates. Instead the cut is in the cylinder wall.

As per the image above. I've just measured them and they are a bit uneven. They should be 5mm high (enough clearance for the piston rings on the piston) but are a bit less. One a about 4.2 and the other 3.8mm or so.

Ah!

Sorry. the penny just dropped. The inset in the cylinder cover will block the steam from the port above.

That's something I can fix and will. Many thanks

Iain

Apologies for the gap in communication, but I have been enjoying the tender embrace of Covid for the last couple of weeks or so. Still slowly regaining energy but well past the worst.

I have good news and bad news on the engine.

Bad news: I am an idiot.

Good news: Jason is not.

In fact as I revisited the Stuart drawings after Jason's comment, I realised that I'd got my original comparison (at the top of this thread) entirely wrong. In fact, both the design for the chest and the D valve correspond exactly to what I expected from the Stuart. I appear to be unable to add 32nds together with any reliability.

And the actual D Valve is orientated correctly with respect to the drawing and not as I had done in my sketch above.

So there's nothing wrong with the chest and valve apart from the machining errors which amount to 0.1mm /.0.15 mm here and there.

Oh and the width of the slots is smaller than the Stuart, but I don't think that will have much of an effect.

I'm not sure if I will try and trim up the chest to be a little more accurate or just put the damned thing back together and see how it goes.

Thanks for making me check - clearly I was not expecting to have got it right the first time ...

Iain

I've built vertical engine which is at the top end of model and bottom end of useful in size (2 inch / 2.5 inch bore).

Building a boiler for it is almost certainly beyond my equipment and skill set. Buying a boiler is almost certainly beyond my budget.

But I think the joy has been in the discovery (well, frustration, swearing, embarrassment, remaking, tool breaking and so on) not the running.

And if you lurk around this forum for any time at all you will rapidly realise that more or less everyone dances to their own tune! If you want to steam it, steam it! If it just sits there nearly finished and you take pleasure in the work .. well that's fine too!

Iain

Edited By Iain Downs on 26/10/2022 10:05:51

Thanks for all your help as always...

I wonder (Jason) if you are mixing up the design/ actual and design / Stuart?

The span of the ports (edge of one inlet to edge of the other is is 40 mm for the Stuart and only 36mm for my design.

It seems to me that the drawing above is for design vs actual where the actual is more or less right just a few tenths of a mm asymetrical.

I would be delighted (all) to rework the D valve to match the ports I've actually cut, but I must admit I have no idea what it would look like. Any advice on that would be most welcome.

I would also prefer not to rework the eccentrics. They are much more complicated beasts that the D valve or ports.

In terms of pressure, as you saw in the video I was running at about 20/30 psi. I was unable to get much above that - at least so I remember.

In that video the engine was running with the glands stuffed, but no piston rings so it may that there was a lor of leakage.

Jason - if you could check that you are looking at the right drawing, I'd be grateful. If anyone could suggest what the improved dimensions of the D-Valve would be I would be grateful.

Again, many thanks

Iain

Regular readers of the forum may be familiar with my thread on my interminable attempts to build a steam engine, to be found here.

It ended on a high note with me reporting that the damnable thing actually RAN - on air mind you, but it ran.

I wasn't particularly happy with how it ran though, it would not start on its own and could easily be stopped with a little drag on the flywheel. I left it alone for a while, though, whilst other things grabbed my attention (illness, retirement, house sales (in process) - dull stuff).

Now retired (HOORAH!) I'm having a look at this again. I've gone and measured up what I've built and compared it to what I designed and then again, compared it to what I intended to design - and found, um, discrepancies.

I throw myself on the mercy of the court.

So the basic port geometry was taken from a Stuart 5A. Specifically I scaled up so that 1/32nd inch = 1mm. No way was I translating to metric directly!

Now I come to have completed the work, I see that the way I've drawn the ports doesn't directly map to the Stuart design. It's possible (though rather unlikely) that I had a reason for this and it wasn't just a mistake. If anyone could suggest a deliberate reason for the change I would happily pretend it was true and claim intent...!

As you can see from the above, the port widths are a good match for the Stuart, but the separations are wrong.

To add insult to injury, The implementation of the drawings is a little out.

Clearly, that's entirely on me!

Whilst I would be delighted if I could make this work by some simple trick, I think what I will need to do is something like this.

1. Mill out the centre of the chest. The ports are around 5mm deep and the height from the top of the chest to the cylinder wall is around 12.5mm, so I should have plenty of 'meat'
2. Carve out a block of cast iron to fit closely in the resulting space.
3. Glue it in place.
4. re-mill the ports according to the (new) design.
5. smooth off the new surface (fly cutter probably)
6. Make another D Valve.

If there are alternatives (ideally featuring less work - and not involving remaking the eccentrics ) I would be most interested.

For this I have two questions, I think. One. the glue. Whilst it's entirely possible that this will never run under steam, it may, so I would like to pick a glue which would stand steam. I also wasn't sure if I should pick a high viscosity one like JB weld or if something thinner was more appropriate. What would you recommend?

Second question; Should I mill down to the level of the current base of the ports so the glue layer would be at the port level, or should I mill below the current port depth which would leave a layer of iron at the base of the new ports?

Well that's the end of my dark confessions - any help as always will be appreciated.

Iain

Whilst unrelated in some ways, in the (very) early 80s I build an interface for the Apple II for what I think was the Royal Small Arms Factory in Enfield (it was a long time ago), intended to check the rifling on a barrel.

I delivered it and watched them push it down something with a bore of perhaps one inch, only to find there was a lot of noise in the output (rotational transducers mainly), which they ascribed to their hardware and took delivery!

I may have got some of these details wrong as it was over 40 years ago, but it did leave me with a mild interest in rifles.

Iain

Apparently, the numbers come from a competition held by the British Army in around 1850. They are well know in the US for having been used with good effect by the Confederates. Despite the numbers the Army didn't order them - a combination of expense and politics from what I've read.

Iain

I've recently come across the Whitworth Rifle (yes him of the screw thread, scraping and many other things). The actual source was in sort of Alternate Universe Fantasy series by William Forschten (the Lost Regiment) which I can recommend.

Apparently it was incredibly accurate for the time (mid 19th century) with a accuracy of 4 inches at 500 yards. Well, it sounds impressive to me and gun buffs appear to salivate.

What intrigues me is that it has a spiral octagonal bore. Apparently because something which is flat is easier to measure than something which is round.

I can't quite get my head round how you can make an yard long octagonal bore. Well pretty much at all, really, let along with what must have though level accuracy.

I have NO doubt that someone on here knows though ...

Iain

I have a cheap USB microscope which has variable magnification, but it's built to a price. It's hard to change the zoom and focus without seriously moving the image.

I've also got a trinocular microscope from AliExpress which cost a little over £200 (£220 if I have it right).

For reference it's here but there are many more there with similar

I got this for use with watches and I have been happy with it so far. I picked a *.5 bowler lens which increased the objective distance from 4 inches to 8 inches to allow me to get my hands and tools into the watch. It also reduce the top magnification from 100 to 50. YOu can go the other way and put A 2X bowler on taking it up to 200x peak magnification.

Being cheap, I built my own sliding stand (all of the metal was in my stock box or it would most likely cost more than buying from china).

I also bought a cheap web cam, removed the case, added a new one and an appropriate reduction lens (0.3 in this case) and got the camera port working for MUCH less than the price of a camera from China.

I am very pleased with the whole set up ( and someday soon may start to use it in anger!). Perhaps the image quality of the camera would be better of the field of view wider with a special camera, but it works well enough.

One thing - microscopes and especially cameras are complicated things. It is very easy to buy bits that don't really work together. You Tube a lot.

Iain

Just a note for those who don't check the sales ads. There appear to be three of us currently offering Model Engineer Magazines for free (YES FREE). I admit I tried to get a bit of dosh, but to be honest I just want them to go to a good home.

I'm near Harrogate, Geoff Warner near Nottingham and Reginald Johnson in Tolpuddle, Dorset.

Surely someone would like to kick start their model engineering!

Check out the For Sale section

Iain

This is a bit cheeky.

At the grand young age of 64 I have handed my notice in and will retire from the work battleground in a couple of months.

We will be downsizing and I am allowed to using some of the released capital to purchase a better lathe than my current Chinese 7x14.

So if one of you even more mature gentlemen is looking to dispose of bits of their workshop and want better than pence in the pound, I would be delighted to hear from you.

This isn't immediate. House sales are taking ages to go through even if the house itself is snapped up.

Like I said, a bit cheeky

Iain

I believe (though only through what I've read), that the correct approach is some pegwood and fine grinding paste.

Iain

Thanks for all the advice.

I attempted to re-glue (and bolt) the original, but the loctite (superglue) set almost immediately on contact and before I'd got the bits in place, so the join was a fraction off and the tubes no longer went through. I did think about trying again, but there's this saying about flogging a dead horse.

So I made another.

This is 2 pieces rather than 3 - the horizontal rail support is no longer split, though there is less meat around the tube. But also not much load.

It all seems to work OK. I expect I will rotate it (on the largish thrust bearing, it's very smooth) more than slide as the sliding is a bit juddery. I've got some PTFE spray and will see if that helps.

I'm currently contemplating if I should paint this bearing (black) like the others. The paint hasn't taken that well and I am now well bored with this project. I probably will though.

Thanks again!

Iain

Hi, Nigel. At the moment, I don't see a need to clamp the system in either a rotational or in out sense. There is enough inertia (and resistance) in the system that it's actually quite stable. Before the damn thing collapsed I was able to actually use the microscope and zoom and focus worked well, even with no locking.

The original stand has a simple vertical bar on a base and in that is a circular copper band recessed into the bore. A thumbscrew bears on that allowing the mechanism to be clamped to the bar but without marking the bar.

Hi, Michael. I'm not sure I get what you're saying about the plastic bars and v-block. I think you mean something like this, but I'm not clear.

Neil - at the moment I'm thinking of one or 2 m26r threaded rods through the gap between the horizontal bores possibly with some loctite, though I'm not sure if I would have the time to position things and may end up glueing any positioning such as the tubes - relatively easy .

For the cross hole, I thought something like this

Essentially a rail bolted to the side to take some 6mm (or 5 or 4, not sure) bolts through into the meat of the bearing thing.

I will try this first as it's easier, quicker and cheaper than making a new system, and if that fails I will have a rethink.

A single block of aluminium - or steel - to machine this out of is rather expensive (if I can find one). I've had another thought which would involved making three cylindrical bearings of of material I do have and then bolting them together in some Heath Robinson way I haven't quite worked out yet...

Thanks for all the input!

Iain

The obscure title relates to a sliding microscope mount which I had just finished - or so I thought.

The chunk thing on the right is a cheap (ish) but surprisingly good trinocular microsocope. the basic idea is that I can move it in and out of my watch-repair (well so far, watch destruction) box as I need it.

The block in the middle at the top of the bar allows for sliding the scope in and out (left and right), rotate the whole thing around the vertical and move it up and down to get the microscope in focus range. there's a clamp underneath to se the height.

Smugly, I took this picture and then decided to take the microscope assembly off and fit the thrust bearing that is intended to reduce wear....

The result was not all I'd hoped.

Sadly, the above picture is not prior to assembly, but after self-disassembly.

I didn't have any stock big enough for what I suppose is the central bearing, So I glued (loctite 638) 3 bits of aluminium bar I did have as you can see above then bored (the two horizontal holes on the mill and the cross hole on the lathe). The horizontal holes are 28mm with 25mm internal bore slide bearings inside (2 each tube). The cross hole 40mm to fit a 40mm silver steel bar I had lying around.

The obvious fix is to glue it back together.

However, one of the issues I had with this is that the stainless steel tube is not exactly precision ground. It's neither particularly straight nor particularly regular in diameter (variation of 2 -3 thou and generally oversized) along the individual 500mm lengths.

It took several goes on the lathe with some emery to get the assembly close to running smoothly. Hampered by the tubes being longer than my lathe bed.

So my first worry is that if I don't get it perfectly aligned when I refabricated it, then the moderate stickiness at some points in the travel will become complete blockers.

The cross hole is arguably worse. The tolerance here is less important, but there is clearly insufficient meat for the glue (each land is about 4 - 5 mm wide I think). I would plan to put a bolt through the centre between the horizontal bores, but harder to see how to do it for the cross bore.

Finally, I was clearly not paying attention to tolerances which I designed this. I assumed that a 25mm tube was, in fact, 25mm and straight. Clearly not, so I wonder if I should re-build the slider unit. Buy a big piece of ally (or steel) Forget the bearings and bore the horizontal holes a with a bit of windage so the steel tubes are a (very) free running fit.

MY concern here is that metal on metal isn't ideal (say stainless on aluminium or steel), but on the other hand, the slides will likely be used a few times a day and I expect would see my days out without getting to the point.

Any advice or suggestions would be most welcome!

Iain

I've been using OnShape for a couple of years now. I agree that the learning curve is steep (and I'm still on it), but I found it easier to get to grips with than a few others I tried at the same time.

I expect I'm not using it as an engineer would, but it does enough for all the things I want to do.

I actually really like it and I would certainly recommend it as an option. Especially as it is free if you don't mind exposing your jottings to the universe. If anyone is mad enough to steal my models, they deserve everything that happens to them!

I think there are a few other users and it does pop up from time to time, but I agree it's not as popular as many. Perhaps because it's the new kid on the block...

Iain