What Did You Do Today 2021

Started on my next project; Scotch yoke engine designed by Bob Middleton..

George.

Started on building a Potty mill horizontal engine. I decided to make a few bits diferent to drawing like the conrod which I didn't like the shape so made my own style.

Made in four pieces and silver soldered together. Bronze end pieces and brass shaft.

David

Interesting project, Mechman - I don't think Scotch-crank engines were ever very common, but I've an idea many that were made, were matched with a water-pump or air-compressor, all in line.

'

Looks good, David .

Fabrication as you've used could be a viable way for me to make the 2 con-rods for my wagon engine. I'd envisaged using round stock, but would be machining so much away it would be easier and more economical to use rectangular bar or plate as you've done.

I like the fluting - with a ball-end cutter?

What material is the base-plate?

'

For me -

I succeeded in repairing my steam-wagon's chimney saddle (I'd blown a weld through the fabrication), and fitting the flange that holds the chimney itself.

The Edwardian photos of the original suggest the chimney was no more than rolled sheet-steel, parallel, with a simple bead round the top - more functional than elegant. It looks as if the builders bought the material from a stove manufacturer. No fancy copper capuchin to polish!

I had found for it a scrap roller-blackboard roller made from wrapped-seam steel tube, luckily so close to the size scaled from the photo that I needed look no further. The rivet-counters won't notice.  

The flange is held to the saddle by 6 tiddly little M4, round-head 'Torx' screws I'd recovered from scrap electrical equipment. Painted, they will resemble rivets, but will be hidden by the flange and the surrounding superstructure anyway. The saddle spigot is far too thin for tapping, and anyway holds a small extension on the chimney below its own flange, so I drilled and tapped both layers of steel together, tightened the screws then set the assembly in the lathe to trim the screw-ends back to the wall.

The flange bolts will be visible, so though screws for now, will be studs and extended-nuts. This is as much for removing the chimney for transporting and storing the bulky model, as representing what was probably original; and I was careful to orientate them for tidy appearance plus maximum accessibility. 

Edited By Nigel Graham 2 on 09/03/2021 22:48:40

What did I do today? First of all I was working, as some money needs to flow into the account. Then - Well I put my lathe into the 'classifieds', but so far no piep.

At lunchtime I looked into Chester Hobbbystore and saw a DB7VS (ex showroom) including stand for £855. While I compared the technical data with the machine I am actual aiming for the offer was gone - somebody grabbed it. This didn't really make my day...

Will go in my workshop later and keep on with my old machine. Current job: make a crankshaft for my little twin study. I will build it up from 7 parts.

Actually cut some metal to day, for a change from being a couch potato. So now have four blanks, awaiting facing and counterboring, out of the 19 needed, for a John Ashton Universal Screw Modification Fixture.

Started with the M3 and am working upwards until 5/16 or M8 is reached. In this way each tapping drilling acts as a pilot for the next size up.

Given the present rate of progress, it should be completed in time to exhibit on the Club stand at a local Show; probably December!

And then there is the Reversible Roller Box update to be done.

No point in rushing things

Howard

Machined the venture for my wagon's chimney - there isn't really room in the smoke-box for a broad petticoat but I've achieved something near.

The only reference I could find to help me design it, is a single diagram and brief notes in Martin Evan's Model Steam Locomotive Construction - but the 1-in-6 part he gives, applies to a short loco chimney, not 20 inches of nearly-3-inch diameter stovepipe. His advice probably relies on relatively much higher blast pressure, too, than my engine is likely to produce. Still, I managed something.

I've a little finishing work on it, but it's another step forwards.

The material didn't help me much though. It was a tubular iron casting good enough for a chimney choke but useless for fine work. It looked as if poured in a fence-post hole, and is so rich in blow-holes I reckon they cored it with a wet loofah.

The St Albans DMES club zoom had 36 on, well into page two of the wall of faces. We had guests from 3 other clubs who enjoyed the talk by Malcolm on his twin cylinder steam engine design. Starting with 1/2" bore but only 1/8" stroke it doesn't give much room for the ports so it was also a lesson in breaking 1mm end mills.

Two days later and another long club night zoom session this time with Exeter DMES. The great thing about club zooming is that it is location agnostic so I can join from 250 miles away. There is a ot of potential in this if you only try it. We have been able to have a remote speaker who would never be able to come to an actual physical meeting.

I think the 1 in 6 defines a minimum length of chimney, more is not very disadvantageous. It works out at having a chimney at least 3*diameter, which is easier to imagine. Similarly, the 1 in 3 defines the maximum height of the choke, having it lower won't cause problems except for tube sweeping. Porta had his right down level with the blastpipe. He must not have been involved in tube sweeping!

Thank you Duncan.

I'd no sooner managed it than what happens?

The latest ME plops through the letterbox, complete with Norm Norton's more comprehensive article on designing locomotive chimneys.

This only confirmed what I'd feared when I looked at the finished choke a few kWh later,. I have made it much too large.

The only consolation is that the casting I used was a scrap item from somewhere, and of too poor quality for precision machine parts.

Unfortunately too, there is a big difference between Mr. Norton's project and mine; so I don't know how applicable the formulae and geometry will be.

His is a 5"g 'Britannia' - a simple-expansion 2-cylinder locomotive pushing a near-constant stream of healthy vapour at some pressure through a venturi only a few inches from the valve-chests.

My 4"-scale wagon's engine is a mid-mounted compound, and by the time what had left the boiler as un-superheated steam has found its way through the engine then something near two feet of pipe to the smoke-box, it will probably be wet fluff needing helping up the spout.

I have just produced a new drawing, to Norm Norton's advice (and will also fit a blower to his design); but I have also placed an appeal for advice on the TE section here.

'

I made the chimney cap-ring last night- more swarf than item - to resemble fairly well the original's basic beading. Today I cleaned the lathe down and started modifying the wagon's flywheel I'd made, ooh, ages ago but recently realised was too heavy. (I'm simply thinning the over-thick web and rim.)

Installed a DRO for drilling depth measurement to my SX2. Was straight forward and I am happy I did it. The crankshaft I had started to look at has to wait, as I have sold my lathe. Went in less than half a day. Of course I am asking myself if I didn't ask enough for it, on the other hand the new owner should enjoy it. I am now "latheless" until the 25th of March. No fear, my wife can easily fill the spare time with DIY projects...

Edited By Gerhard Novak on 15/03/2021 21:20:39

Did a bit more to Potty mill. Turned the flywheel and finnished the parallel running gear.

Nigel

The base is an aluminium plate.

David

Thank you David. it looks good!

You've given me an idea for fabricating my connecting-rods, though with a circular-section middle, and possibly welding as I'm not sure I can heat fairly hefty lumps of steel adequately for brazing.

Been doing a bit of cold blueing of Myford ML7 parts. I've previously tried a Jenolite paste blue which did work, but not a great finish, so I splashed out on some Phillip's Cold Blue Solution and I'm much happier with the results. Method used is as follows:

Immerse part in general purpose thinners (modern equivalent of cellulose thinners) and shake it around for a bit to degrease.

Remove from thinners with tweezers, wipe with paper towel and hold in the flame of a blowtorch for a few seconds (until any condensation disappears).

Immerse in solution - I used about 1 part blue to 2 parts tap water - and then, what I think is the most important part, keep brushing all surfaces with a new, clean paintbrush.

Keep doing this for at least five minutes, I went as high as ten minutes on some parts.

Remove from solution, dunk in clean cold tap water.

Remove and spray with WD40, then use fingers to liberally coat all surfaces with new motor oil (20W50 as I had some handy, not synthetic).

Leave for about 24 hours, wipe dry and apply a thin coat of Renaissance Wax with fingers, wait a few hours and buff with soft cloth.

Lovely dark blue, almost black finish that seems to improve slightly over the next few days. I think the heating and brushing are the key points to make it work well.

Rob

Thoroughly vacuumed the bedroom carpet.

The relevance to engineering?

The steel swarf glinting in the bright morning sun!

++=

Rob -

Thank you for that report.

It was hard to track down blueing chemicals, and eventually I found Birchwood Gun Blue in a country-sports supplier's catalogue (after turning the PC's search filters down to permit the G-word). This was for my Worden T&C Cutter parts.

The results are a bit patchy but that was me, not it, to blame.

The necessity for thorough cleaning was soon clear, as is protecting the blue, or more black in my case, steel immediately afterwards from all those promiscuous Oxygen atoms. I used white-spirit then a wipe with xylene paint-thinners; and applied the blue with cotton-buds.

Being for a grinder, I could not use oil or grease, but spray-on furniture-polish seems satisfactory even on unprotected steel for quite a long time (for indoor use - the grinder will live in the front room though my house still has plenty of rust germs.)

Nigel - yes, I had seen on YouTube that selenium dioxide solution was the stuff to use, and that Ebay was full of people selling it for pennies. However, I couldn't find any, so went for the Phillip's product instead. Furniture polish sounds a good idea though. In the dim and distant past, I have used Birchwood Casey's Gun Browning paste, which worked well, but I don't think brown looks so good on machine parts.

Rob

The recent discussion about vernier height gauges prompted a thought. The problem I have with my vernier gauge is that a) It can't be zeroed and b) more importantly it's really hard on the knees since I have to squat down to read the scale through the bottom part of my varifocals. It occurred to me that I have a caliper type scale left from my budget milling machine scales. This is what I made:

Not particularly elegant - made from the oddments box. I checked it against my workshop gauge blocks and there appeared to be a slight systematic error checking up to 4" height. I then had the thought to check the verticality of the scale against a square and after a tonk with a hammer it reads 4.000" and 0.500" against the appropriate gauge blocks. I am very pleasantly surprised and it's definitely good enough for marking out and it cost me nothing. Although the scale is hardened stainless the body is not since I had no problem drilling and tapping for the thumb locking screw.

Cheers,

Rod

Continued on with pieces for my Scotch yoke engine; did the piston rod & piston. A note to others FWIW, after careful reading of the dwg I decided to make the piston in two peices, why you ask?.. well the piston OD is 26mm, the undercut for the pistonring is 19 mm, the ring is to be made from Nylon or PTFE , now tell me how to fit a 19 mm ID over a 26 mm OD without splitting the ring, with the correct gap, to ensure a seal.

I decided to machine the piston as per dwg but machining the outer/top part as a seperate flat plate. As the piston assembly is tapped M5 it all screws together to become one unit with the ring captive. Will take pics later.

George.

Today I managed to puzzle my way through the worst Chinglish I've ever seen to find out how to set the top pressure in my compressor. Previously, it would run hit the end stop and keep running as the overpressure valve cut in. Take of a nasty plastic cover and turn the nut counter clockwise till it turns off a bit below 8 bar. None of those words being in the instruction.

Also grew my compressor tools skills slightly, but finally ordering a coiled extension with the right (Euro) connectors on. I now have an air gun by the mill and by the lathe.

That and a little bit of tidying up left me with a feeling of progress. I also started on the 3rd version of my reversing link and have yet to mess it up. Plenty of time yet.

Iain

Iain - not keen on those coiled hoses, I would advise saving your money (if it's not too late already)

Rob