Bolton 12 Beam engine from scratch

[ShopShoe]

deeferdog,

Thank you for posting your shop pictures. I am sure I am not alone in liking shop pictures, shop build logs, and shop descriptions.

"Of course I filled it all straight away" Of course ......

--ShopShoe

 

[deeferdog]

I am now happy to report that I have finished the governor, this part of the model proving a real stumbling block. My attempts to turn two brass balls that look the same were a miserable failure and a waste of good brass, another job that was just going to be too easy, sigh! In a blinding flash of inspiration I went to the local fishing shop and brought a bag of heavy lead sinkers, lovely ROUND ones and used two of those. Cheating I know but they sure look better than anything I'm going to come up with. Things didn't improve when I spun them in situ and found that they hit the side of the beam connecting rod. The only solution to this was to re-machine the flywheel and governor gears to move them along the shaft, make a new mount for the governor gear arch and reassemble everything. On to the next problem, by this time I was heartily fed up with the this part of the project. Lucky the engine is now too heavy for me to throw. I shut up shop and contemplated my failures over a scotch.
A new day and a new start, things went much more smoothly and most of the parts fitted. It would have been much easier working off drawings and once again I promised to work on my CAD program a bit more. In the end it all seemed to come together and the result is OK. I put a spring on the shaft but this will possibly be removed if it proves not to be necessary. I am really pleased that this part is finished and I can move on. The parallel linkage is looming and I sure hope it proves a bit easier.
Regards, Peter.

 

[deeferdog]

Before tackling the parallel linkage, the entablature must be fitted. When I first started this project I thought that this part would have to be fabricated along with everything else, however the kind donation from John of his surplus parts included this item. The casting is very good, I'm a bit wary of these now after my experience with the beam and have a lot more respect for those who make machines from casting kits, however as I said, this is very good with no distortion. When I made the bearing platform, this sits on the top of the column, I machined a concave profile into the edge but the casting has a square channel profile so I removed the platform and after drilling and attaching the entablature, I matched the square profile into the platform's edge. The drawings called for the supporting column at the end of the entablature to be attached to the top of the cylinder head but I decided to drop it all the way down to the base so I machined a piece of brass hex to do the job. The result looks pretty good in my opinion and I was pleased that the beam appears to be in the centre of the entablature, this should help with the parallel linkage as it has been mentioned by others that the space between the entablature rails can get a bit tight. Oh well, find out soon enough I suppose. Regards, Peter.

 

[deeferdog]

With the entablature now in position I can turn my attention to the parallel linkage. I have decided not to make this as per the drawings as the style looks complicated for no good reason that I can see, I have decided to use a simpler design. After taking some measurements the bend in the beam was starting to make life difficult, in fact I could see that something had to be done. All of the fault lies with me, I should have sat down and thought about the whole thing when I first noticed the error instead of just blundering on. I removed the beam and made a strongback from a piece of steel channel and bolted down the beam. I understand that cast iron can build up large internal stress during the cooling process after casting so I supposed that that this was the cause of the warpage rather than a bad mould. Firstly I clamped it flat and then heated it to just under a colour change, then added roughly 1mm of bend in the opposite direction to the warp. I only had the propane torch so I new I was going the struggle to get it hot enough, I would have liked to get it to a very dull red. Centuries ago, when I served my time, I spent a week in the blacksmith shop, now I wished I had paid more attention to the old Flight sergeant, he talked about cast iron the way most talk about their first born. I hoped he wasn't looking down on me. Anyway, I did my best and did achieve a bit of red in the main area of the warp after nearly an hour of heating, nothing left to do but let it cool and hope it doesn't crack. Cheers, Peter.

 

[Cogsy]

Maybe if that doesn't work set it all up again as you have done, then build a nice hot bonfire and jam the whole thing in there (like right into the heart of the coals). Keep it burning well for a few hours, and leave it to cool down in the fire on its own. I know people have done this sort of thing with success on chilled castings to improve machinability so it should be safe for you to try.

 

[deeferdog]

Thanks for the advice Cogsy, but if I had room for a bonfire I'd have a bigger shed. The beam has cooled and it looks promising on a quick inspection, will post more results tomorrow. Thanks for your time, Cheers, Peter.

 

[Cogsy]

Ahh, that's a good point I guess. I forget sometimes that we don't all have at least a 1/4 acre to stretch out on. I guess if you get desperate at some point there's always a camping trip into the bush...

 

[deeferdog]

The cooled beam looked OK by eye but I'm a much wiser and more sceptical hacker than when I first encountered kit castings. I set the beam up in the mill and ran the clock over it. Some problems I could correct by re-machining, some were inherent in the original mould, such as the bosses being offset from each other. This error means that a centred hole on side A of the beam will be off centre on side B. Nothing I can do about that but it makes you wonder if these things ever get checked by the manufacturer, this casting kit costs over $A2000 and if I had paid that amount I would be more than a bit annoyed. By the time I had finished all the checking, re-milled all the bosses and re-drilled and reamed the holes I came to the conclusion, as I always seem to do, that if I had just spent a bit more time with the beam in the first place it would have saved me all this heartache. I re-assembled the beam and engine and the result looks a lot better. I turned up a couple of test joiners for the parallel linkage and started to take a few measurements. Things look OK so far, I just need to apply a little patience to this job, a pity patience can't be brought. Regards, Peter

 

[deeferdog]

Making the links for the Watts linkage entailed a lot of fiddly machining with small pieces of brass and whatever was lying around in my junk box. The whole arrangement gets very tight where the two front links pass the two fixed parallel rods that are attached to the entablature. The fact that the beam was now reasonably straight has helped here as the alignment between the beam, column centre bearing and the crank is critical to the beam passing through the centre of the entablature. As I said in an earlier post I have decided not to follow the drawings on the design of the links as I thing they are a bit over fussy for this engine. The end result looks reasonable I think and seems to operate quite well. I ran the engine for about half an hour using the battery drill and everything seems to be quite free and willing to turn. Here is a link to a quick video of the result. Cheers, Peter. https://youtu.be/oZDHZmPWKIA

 

[deeferdog]

After the parallel linkage, the next looming challenge was the throttle. The drawings are quite good here, they are on the last page and have obviously been redrawn by a competent draughtsman, something the rest of the drawings could benefit from. The throttle is combined with the shut off valve and that didn't suit the layout I had in mind so once again I decided to go it alone. For the throttle I proposed to use a small ball valve I had lying around. To make it operate smoothly I backed off the pressure on the ball by slightly undoing the assembly, then used Araldite to make the thread gastight. The valve is now virtually frictionless, I hope it will work as a throttling valve as I notice the one in the drawings is like a butterfly valve. Any advice here would be welcome. I made a small column from 12mm aluminium and fluted it for effect, this would be the mount for the throttle. Much fiddling about making the linkage from the governor to throttle arm and I don't think it's quite right yet but I will adjust as time goes by. Next I will run the copper tubing and mount the needle valve. The end is in sight. Cheers, Peter.

 

[Crisptrans]

Peter, phenomenal job on this engine! I've been reading through in awe. Chris

 

[Cymro77]

Peter,
Great work! Your inventiveness for alternative options is enviable. Thanks for sharing - I have been following along envious of your skills.

 

[deeferdog]

It is with some surprise that I realise that this engine is close to completion nearly nine months after I started it, but there is still a lot of work to do, not the least is getting it to run. Firstly let me say thanks to those who have heaped praise on my work, I'm not sure it is justified but it is still very nice to receive those comments. OK, onward to the engine. I ran the tubing to the governor through a needle valve and mounted it to the base, the connection is a standard airline fitting. From the governor to the steam chest will require a little thought as the flanges I made for the connection a proving a little fiddly. Because people generally like to see model steam engines operate, and because connecting them to steam or air at odd times is such a hassle, I generally incorporate a motor into the model. If I can, I like to disguise it, make it look like a generator that the engine is connected to perhaps. Because this engine is so big I just decided to add a small 12 volt DC motor and scuttle my previous plans for a rope drive. I had a belt from a small electric planer so I used this and copied the design of the pulleys. The motor is 60 rpm through an incorporated gearbox, cost around $A18. I machined a case with feet attached as they can be a bugger of a thing to mount, then made a mounting platform and attached it under the layshaft. I was having a good day and all went well. Those little grooved belts are marvellous, the motor turned the engine with no trouble, draws around one amp and ran for over two hours as I twiddled, tweaked and oiled as it ran in. Terribly pleased with the whole thing, I can't really believe that I built it, I'm only a hacker but I love it anyway. For those that love seeing levers, cogs and cams going up and down smothered in oil, here is the link, https://youtu.be/cnlEqV1ZaAc. Next is to get it to run on air. Cheers, Peter.

 

[deeferdog]

Finally got the engine running on air. The way I had made the slide valve was all wrong as JasonB had pointed out in February. I went back in this thread and reviewed what he recommended and remade the valve as he suggested, consequently it now works. The only thing I can mention in my defence is that there is nothing at all in the drawings about the slide valve other than an un-dimensioned side view. My thanks to JasonB. The timing of the engine is poor and the eccentric needs to be adjusted, however, clever engineer that I am, I have keyed that to the main shaft, bugger! Anyway, to cut a long story short, I made a list of all the things that need to be corrected before commencing the painting. To repair the eccentric I have decided to make a new main shaft as I have changed my mind so many times with this that it now looks a muddle of slots dimples grooves and keyways. I'll re-bore the eccentric and fit a new centre with grub screws that will allow for rotation on the shaft. Further, I intend to countersink all the cap screw fastenings, fix the keyway in the main crank, re-do the piston rod packing gland, make a better job of the tubing, yadda, yadda, yadda, the list goes on. I am determined to finish this engine to the best of my rather limited talent. That's it for now, here is a link to prove that I did get it running on air, https://youtu.be/sKKRXM6jESw, Cheers, Peter.

 

[deeferdog]

The various repairs and reworks that I mentioned were done as I dismantled and cleaned the engine prior to painting. I inspected each part and did a bit of file work or sanding as needed, then each piece was washed in hot soapy water to remove grease and oil. The parts were dried out in the sun, then each were wiped down with thinners. I had decided to use the Dulux Epoxy spray paints, the etch primer and the top coat "Brunswick Green". This is a much darker green than it appears in the pics. When I assemble I will use the Loctite 263 where it is needed and the Cyberbond flange sealant for the gaskets. All the surfaces that need sealing I have lapped with 1200 paper and kero on my flatstone. As I write this I am about half way through the painting and all has gone quite well. I'm no Rembrandt but these spray cans sure have come a long way and I find that it is fairly easy to achieve a reasonable result. I'll finish the painting and then on to assembly. Cheers, Peter.

 

[deeferdog]

Finished. There is little more that I can do. A project that I commenced in November of last year has come to an end, and I am pleased with the result. At the start I seriously doubted my ability to see this through, in fact that was the main reason that I did not consider buying the casting kit. (Plus it was over A$2000). Over the months of building this, my skills have improved markedly and my tooling has benefited. I estimate that I spent roughly 900 hours at the task, the materials I suppose were around A$400 to A$500 and all this begs the question, was it worth it? For me the answer is a resounding "yes!" The sense of satisfaction I feel when I look at the engine is priceless. The project led me to this forum and I have enjoyed writing about it almost as much as the building, and the exchange of ideas and help that I have received from other members is something that has given me a lot of pleasure. I would like to thank sincerely all those who took the time to post comments on my progress, it has made me feel part of a group of people whose common interest binds us together. To anyone who may be reading this and considering a bit of a machining challenge, my advice, for what it's worth is "go for it", the end result is sure rewarding. Thanks again to all who followed this journey, time for a drink. Cheers, Peter.

 

[apointofview]

That is a beautiful engine you have built ! Congratulations !! Thanks for taking the time to take pictures and document your work. It's a great help to me to see how other guys carve away at metal and make wonderful machines.
Could you do one more thing and show us a video of it all done running on air ?
Pete

 

[SilverSanJuan]

WOW! That turned out amazing! Beautiful craftsmanship all around. Thanks for sharing the journey with us. :thumbup:

 

[Cymro77]

Peter, a beautiful engine. Great work - thanks for sharing!