Burrell Single Crank Compound Traction Engines - 4" Scale

[jadge]

Yep, been sorting out some remaining work issues and handing over some parts I've made for a glider restoration. Also making sure I've got everything ready for a trip up north with the glider soon. I can confirm that the parts shown will be available for inspection at SCMTEG in a few weeks. 

Andrew

[jadge]

Having made the crosshead and slidebars I'm keen to get on and start machining the cylinder. As a precursor I decided to update my 3D CAD model. Big mistake! I've spent ages correcting errors and accounting for the vagaries of the casting. On the drawings the cylinder and other parts are shown leaning back slightly to the crankshaft, specified variously as an offset or an angle. At the start I decided to bin this idea as it would make machining the cylinder unecessarily complicated. Having modelled the cylinder to get the vertical centreline of the engine in line with the crankshaft two problems arose. The flange on the bottom of the cylinder was only 1/4" thick. It would be strong enough, but is much thinner than prototype and wouldn't allow the flange to sit above any sensible thickness of cladding. The second problem was that the outer slidebar support casting was unusable - too tall. So I tweaked the cylinder model to lean back by half a degree. All the problems went away! The flange on the cylinder base is now about 1/2" thick and the support casting is right. On reflection it won't make the cylinder more difficult to machine. I can machine everything square and then at the final stage of machining the bottom of the flange just tilt the whole cylinder a bit. On the fullsize engine the cylinder tilts back slightly. So presumably the designer had the same issues of getting the cylinder to line up with the crankshaft.

On other forums there has been a discussion on what thickness of gasket to use. Although my steel boiler is made from hot extruded tube the diameter only varies by about 4 thou around the circumference. Most advice was to use a 3mm or so gasket. That seems very thick to me; I think I should be able to get away with a 1/32" gasket. To check the fit of the flange on the boiler I 3D printed just the flange from my CAD model:



I can get a 5 thou feeler gauge in between the flange and boiler in places, but generally the flange is a very good fit. More experimentation is needed, but this is a good starting point.

Some years ago I bought a face mill for the horizontal milling machine. This will be useful for roughing out the cylinder. With much BF and BI I have finally got the overarm on the horizontal mill out of the way:



Now that I've got some oil on the dovetails I can move the overarm just by pushing rather than walloping it with a copper mallet. I've also had to make a new drawbar for the face mill; M16 instead of 5/8" BSW. I might even get around to trying out the vertical head for the mill I bought some years back on Ebay:



The main issue with the vertical head is how to lift it onto the machine. That's a 12" rule leaning on it. When I bought it I managed to lift it out of the car boot and into the workshop. No way I can lift it unaided now.    At least temporarily I can get my neighbour to give me a hand but longer term I need some sort of mechanical assistance.

At the moment, partly by design, I don't have any work lined up for a few months. So once I've got my gliding holiday and my mothers 90th birthday bash out of the way I should have plenty of time for the workshop. Of course there are other calls, like the garden and house, but I can control the urge to do those jobs. 

Andrew

[Jo]

I might even get around to trying out the vertical head for the mill I bought some years back on Ebay:



The main issue with the vertical head is how to lift it onto the machine. That's a 12" rule leaning on it. When I bought it I managed to lift it out of the car boot and into the workshop. No way I can lift it unaided now.    At least temporarily I can get my neighbour to give me a hand but longer term I need some sort of mechanical assistance.

For my Harrison Vertical head fitting I have a board that mounts through the spindle and allows the head to safely stand vertically for lining up to the front of the machine. Getting it off the floor originally needed a crane but once on the board it can be moved around on my roller skate. You could easily do similar with that Andrew 

Looking forward to seeing your progress at the end of the month 

Jo

[jadge]

If I had the head on a stand at the same height as the table I could probably lift/slide it across. That's what I do with the dividing head, although I think the vertical head is rather heavier. Question is, have I got room for a small table?

Oeeeer, I'd better stand outside the hall while you and Jason inspect the parts and wait to be called in for the verdict. 

Andrew

[Jo]

This is my high tec head stand for the Harrison. Skillfully painted silver to stop me thinking it is a suitable candidate for the log burner. The thread in the top is for a drawbar through the vertical head. 

I have an over head crane for swopping over the Theil head as it is above head height 

Oeeeer, I'd better stand outside the hall while you and Jason inspect the parts and wait to be called in for the verdict. 

This is your last chance to do this. I am sure Jason is going to be very disappointed he won't have so many opportunities to prove his engines are better than everyone else's and show how well they run If he is too critical of your stuff ask him if he is enjoying himself still having to work for a living 

I said work  what a horrible thought   

Jo

[jadge]

If I do make a table I'll probably weld it up from steel tube.

It's a shame it will be the last meeting, but there are some things I won't miss. I'd better clean up the rear wheel though as it's got some rust spots on it. That's due to it being wet, wet and more wet at Forncett this year when I was unloading and loading my exhibits.

Andrew

[jadge]

When I riveted the spokes on the third rear wheel recently, the riveting proved to be more difficult than before. For some reason I had problems getting the riveting fixture aligned and the rivets didn't seem to close as nicely. Turns out the reason was simple; the bench top on which the fkypress sits was broken. 

The bench top is two 18mm sheets of MDF glued and screwed together. The bottom layer was badly cracked, meaning that the flypress was leaning backwards. Hence the alignment problems. Some while back I was given a piece of steel plate (600mm x 500mm x 15mm) from a failed aircraft project. I thought it'd make a good base for the flypress, and hold the bench top together at the same time. Drilling on the Bridgeport meant somewhat of an overhang:



I drilled and countersunk a pattern of holes for M12 screws. I also chain drilled and bored a 90mm diameter hole to match the hole in the base of the flypress. Here's the plate in place on the end of the bench:



And with the flypress installed using M16 bolts:



The whole setup feels pretty solid, and rather better than it was originally. I plan to assemble and rivet the final rear wheel over the next few weeks, so time will tell how well the plate works. It's also the first time that I've acquired something that turned out to be useful after someone said "do you just want.............".

Andrew

[mike mott]

It's also the first time that I've acquired something that turned out to be useful after someone said "do you just want.............".

That does not happen very often for sure, most often they are just trying get rid of it.

Mike

[jadge]

That does not happen very often for sure, most often they are just trying get rid of it.

Definitely been caught like that. I normally end up giving the stuff back, recycling it, or in the worst case paying the council to take it away. 

Andrew

[jadge]

Annoyingly the last few weeks haven't gone according to plan. Although I haven't been working I don't know where the time has gone. Can't remember if I said I've converted nearly the whole house and workshop to LED lighting and finally fitted the outside lights at back and side. Everything is much brighter now.

I have finally finished the last rear wheel; man that's a relief. The riveting went much better with the heavy steel plate under the flypress. I now have one engine sitting on it's proper wheels. The rear axle has also been machined to final length (the drawing was wrong by more than 2") and keys and pins fitted. The other set of wheels are lurking under the hall table prior to having rubber tyres fitted:



I also got around to cutting up the 2m by 1m sheets of 3mm, 2mm and 1mm steel sheet that have been stacked down the side of the bungalow for a few months. Good job I sprayed them with WD40 before stacking. I had a few issues getting the guillotine going. First problem was I'd plugged in the wrong 3-phase plug, then didn't turn it on.  Finally I had some problems with the electromagnetic clutch. I had issues with it a while back which I traced to worn brushes. I fudged it but didn't put the covers back. Turning on the nearby lathe had resulted in swarf sitting on the clutch shorting out the brushes. Two passes with a small paint brush sorted it. Thank gawd for 1960s electrics that shrug off a small thing like short circuits with nary a problem. I was a bit surprised because the 3-phase to 90VDC power supply has a selenium rectifier in it, which have their issues. Here are some, but by no means all, the sheetmetal blanks, with a 24" rule for scale:



Having guillotined the sheets I've been experimenting with hot flanging the 3mm sheet to form the spectacle plate and front plate for the traction engines over a steel former. A couple of quick trials on the corner (the difficult bit) gave me encouragement to try the real thing. One thing I did learn was to make a really crude wooden mallet to limit marking the metal as opposed to the original copper mallet. The real plates were a mixed bag, one disaster, and one sort of ok. After some machining here's the plate in situ:



I'm not happy with it, and think I can do better. I've learnt quite a lot about flanging and how much I need to allow for the flange. I was over generous, especially on the corners, which makes life difficult. I was using a cutting nozzle (without the extra oxygen!) on the oxy-acetylene set for heating. Unfortunately I've now run out of gas. I wasted the whole of last week trying to get refill bottles on the account I have with a major gas supplier. The local Cambridge agents proved to be a bunch of (rhymes with bankers) and they also refused to load my car with oxygen and acetylene cylinders. Turns out there are new EU rules on the transport of dangerous goods. That's fair enough for a lorry carrying many bottles on a multidrop schedule. The rules explicitly exclude individuals using gas for leisure and hobby purposes from having to obey the rules. I've made a big enough PITA of myself with customer services that the sales director at the gas supplier should be getting involved. For more details here's a link to the whole sorry saga on another forum:

https://www.model-engineer.co.uk/forums/postings.asp?th=148478

I've also knocked out the bolts and another batch of nuts for holding the plates in place. I made double the number of nuts, as you can never have too many ¼" BSF nuts:



I've also had a go at rolling a chimney. Two things I've learnt are, allow for the metal thickness when you create the flat pattern for the truncated cone and two, initial pinch rolls do not roll a cone, even with the third roll on a slant. Not even close in fact. It turns out that commercial cone rolls use cones rather the parallel rolls. After some metal bashing and use of Jubilee clips I've got a passable cone. But I'm not really happy with it so decided that I needed a proper former. I considered wood, but me and wood don't get on, much too easy to fudge it up. So I decided to go with metal. I ordered a 500mm length of 100mm diameter steel on Ebay because it was way cheaper than commercial stockholders and I'm not fussed about quality. Here's the setup for drilling a centre in the end:



And turning the taper using the hydraulic copy unit and a hand filed template:



The finish passes were at 370rpm and 4 thou/rev feed, DOC as needed. I had some problems with variable finish and banding, but I'm 99% sure it's the material, not me or the lathe. Surface roughness is 3.3µm Ra which is sort of ok, but not brilliant for EN1A. Still it's going to get walloped with a mallet so I don't really care. Although it's not a chimney I couldn't resist trying it in situ:



I hope that the next few weeks go rather better and that a number of items mentioned here, and some that haven't been, come to fruition. Roll on Tuesday when my gas bottle refills are supposed to finally arrive. In the meantime I need to get on with the disaster area otherwise known as the garden.

Andrew

[jadge]

I have had another go at flanging the spectacle plate with reduced allowances for the flange. Here's the setup, showing the wooden mallet in the centre:



This is the steel former, hogged from a slab of hot rolled steel and the rounded corners done on the CNC mill. As a result of previous attempts I've increased the filed radius along the periphery to about 3/32":



Pleasingly this time around the flanged spectacle plate slipped neatly between the hornplates without any machining being required. So I must have got my sums somewhere about right. Here's the plate with fixing holes drilled and the bottom shaped with the help of hacksaws and files:



And the plate in situ with the previously made nuts and bolts. The holes in the spectacle plate were drilled 6.4mm, so a bit bigger than 1/4". I'm pleased to say that all the bolts fitted perfectly first time round. That's the power of the DRO on the mill:



Cutouts are needed in the plate for the connecting and eccentric rods, and for the governor belt, but I'm not exactly sure where yet as I need to tweak the CAD model. There are also two small holes needed for a bracket that supports the rods for the regulator and "starting" valve. The drawings show the bracket as a simple plate with a slot, but I'm in the process of modelling it properly to reflect the somewhat OTT casting used on the full size engines. Next I need to have a go at the front plate (actually behind the spectacle plate) which is similar but has a smaller radius in the corners; 3/4" versus 1".

Andrew

[Steamer5]

Hi Andrew,
 NICE work on that plate!
Would of liked to see a video of you doing that!!
Not sure if my skills are up to doing it but hey beating a steel plate cant be all the bad for stress relief!

Can you give a few more details on how you went about it please?


Cheers Kerrin

[crueby]

Andrew, did you have to anneal the sheet stock? That came out great!

[jadge]

Andrew, did you have to anneal the sheet stock?

No I didn't even though it was cold rolled sheet. I assume that the mere fact of heating the bend zone before hitting it with the mallet was enough to relieve any stresses.

Andrew

[jadge]

Can you give a few more details on how you went about it please?

Later this week I hope to have a go at forming the front plate with it's smaller corner radius. When I do so I'll take more pictures and create a post that tries to explain the process in more detail.
Andrew