Bolton 12 Beam engine from scratch

[bazmak]

If your running on air then corrosion is not a problem.Any combination
of Alum,brass,bronze, steel or cast iron,but I avoid 2 metals the same
Especially aluminium.You have made a good job of alum cylinder so my
option would be a brass piston.People more expert than me would use
a cast iron liner to the alum cylinder but you can leave as is for now
When the engine is up and running you could consider lining the cylinder
but I would be happy as is for a model running on air with brass piston
With steam its usual to use alum bronze,but its hard to source and expensive

 

[deeferdog]

Thanks for the advice bazmak, I'll make a brass piston. Well, onward and upward I had to make all the linkages for the valve train to suit my model so they don't look much like those called for in the plans. The top cross shaft I made from brass because I think it will look good when, if ever, the engine is finished and painted. The two linkages from the bottom shaft to the top shaft were made from 3mm stainless rod. I machined some aluminium ferrules, milled flats on either side and threaded them onto each end of the rod. I was quite pleased with the result. The ferrules are retained onto the shafts with circlips. This whole arrangement forms a frame which connects to the slide valve shaft at the top and through some sort of connector to the main valve shaft sitting in the bearing blocks on the base.
To make these connecting blocks, I first glued two pieces of aluminum together and drilled the two shaft holes. I needed them to taper in a cam fashion so I set them up in the mill at five degrees with my protractor and ran over the top of them with an end mill. A bit primitive but it worked. The ends were rounded over and rubbed down on the surface plate. The main valve was drilled and tapped for M2 in conjunction with the connectors and SS grubscrews were locktited into place. The bottom frame shaft is a sliding fit onto the connectors. Happy with all that. I think I have reached the upload limit, I will continue with another reply.
Cheers, Peter

 

[deeferdog]

So, just to finish off, the assembly went reasonably well, The gallery block cap screws interfered with the frame at the base so I countersunk them and this fixed that. I hope that I have made the slide properly, (Note, I will relieve it at the edges to allow for better steam flow.) When the frame is at its uppermost, the bottom port is fully exposed and vice versa when the frame is at its lowest, advice here would be appreciated. That's about up to date for now, this morning I drove to the aluminium supply house and brought a 300mm x 300mm x 25mm (12" x 12" x 1") block of metal. I hope for two things, one that I can turn it into a flywheel on my mill and second that my wife doesn't find out how much it cost.
Regards, Peter

 

[bazmak]

Its not usual to make the flywheel from alum as it lacks weight
Brian Rupnow made one and fitted large brass dia weights to the periferie
cheapest way is steel or cast iron or better still fabricate a spoked one
If you look thru engine posts you will get some good ideas and advice

 

[deeferdog]

Bazmak, I think in this case I'll be OK. The wheel is 25mm thick and 300mm in diameter. I really need to do it this way because I want to see if I can cut it out on my mill. I have never attempted anything this large so it will be interesting if nothing else. If I come a gutser, and that's more than likely, then I'll have a crack at fabrication.
Cheers, Peter

 

[Cogsy]

If it turns out to be not heavy enough, it's a fairly simple operation to drill through the outside and install slugs of brass/bronze/lead/steel/etc. to beef up the peripheral weight. The webs/spokes/etc. aren't all that critical so your big lump of ali will be fine. I feel your need to keep the lovely wife in the dark, mine is under the impression that now I've bought the machines and tooling that what I do in the shed only costs electricity...

 

[deeferdog]

Thanks Cogsy, that's a good idea. A bad idea was my decision to try and use a hand wheel as a flywheel, I've got to confess that I don't often machine cast iron and when I do I hate the filthy dirty mess it makes, both of me and the machine. The only thing about this effort was that there was not much mess, very little cutting was achieved because the thing was hard enough to be used as a grinding wheel. I persisted for most of the day but in the end I gave it away, the rim was cast in what I can only describe as a pretzel shape and I could see that even if I broke through the diamond hard crust, (I had been warned, see earlier posts) it was'tn going to ever become a flywheel. Well, not with me fiddling about with it. I have posted some of the pictures for your general amusement, possibly some of you have had similar experiences. I have rescued something from the fiasco, I have gifted it to my beloved as a piece of garden art and it is very true, a happy wife means a happy life.
Back to the aluminium.
Cheers, Peter

 

[deeferdog]

So now the fun begins, a 300 x 300 x 25 piece of aluminium is not what I would normally expect be be machining when making a model steam engine, it will be by far the biggest thing I have had on my mill table, so I hope that both the machine and me are up to it. I marked the centre and drilled then reamed to 22mm centre hole. This will exactly fit the mandrel I had previously made for my rotary table. The mandrel has a No 2 morse taper which locates in the centre of the table and finishes with the 22mm straight shank. This shank then locates into the mounting plate and aligns it to the rotary tables' centre, I then bolt the plate to the table, I hope the picture makes it clearer. The mandrel protrudes through the plate, I place the FW blank with the 22mm hole over this mark, drill and and bolt the blank to the mounting plate and then use the mandrel to locate the rotary table exactly under the spindle of the mill and clamp the RT to the mill table. (This is turning into a novel.)
I wound the table out to 152mm plus half the 12mm ruffer slot mill, checked everything and proceeded to cut. Around 2000 rpm, depth of cut 1mm (40thou) with plenty of fluid seemed to work OK but I had to be careful with the feed as chatter could creep in. I seem to have a bit of backlash in the RT and this coupled with the overhang means that the setup is not as rigid as I would have liked. Still, progress was made and after 25 circuits of the RT I had a slightly oversize round FW blank.
I changed the ruffer to a finisher and planed down to size, the finish looked pretty good so I was pleased with the effort and with the mill, it handled this part of the job, no problem. That's it for now, do the layout and drill some holes tomorrow. Cheers, Peter.

 

[Blogwitch]

Just take it steady mate, the job isn't going to get up and run away. You only get one real bite at a job like this.

So work things out, I use a notepad and write each step down, and follow that. What you don't want to do is trying to work things out in your head and trying to concentrate on the machining at the same time.

Good luck

John

 

[deeferdog]

Good advice, thanks.

 

[Cymro77]

Quite an undertaking - looks as though you did well. Congrats, now onto even more complex things! I am enjoying this since I am faced with similar problems with a "flying wheel".

 

[deeferdog]

I am a novice when it comes to using CAD, however I had hoped that I would be able to lay out the wheel and plot the X Y of the various holes. Well, no such luck, it's beyond me, I messed around for ages and achieved little, even worse, the pathetic drawing I did manage to do refused to print, more wasted time. In the end I got so fed up that I photographed the screen and worked off that. I scribed the pitch circles using the RT and the angles also. The main concern was to make sure that the two bolts holding the blank to the mounting plate fell in the scrap area and not the spokes. I decided to do all the cutting with my 12mm ruffer, so all the holes were drilled using a 12mm bit. Both pitch circles were laid out 1mm undersize to allow for the finisher to clean things up. I experimented a bit on the first cut to see what the machine was happy with, I realise that this a novel approach to feeds and speeds but I do the same on the lathe. It's not hard to see when a machine is overloaded and I like to look after my tools. Anyway, the ruffer was happy taking a 5mm deep cut with a nice easy feed on the RT. I use a water based machining oil (Metalum XPD1800) and I find this stops galling on the cutter. The other thing I do is suck all the chips from the slot after each pass, I find that surface finish is greatly improved, and finally always cut in one direction. Everything went quite well, as each piece of pie was cut out they fell away without any tendency to jam, I'm always a bit fearful of that. That's it for now, onto the hubs and spokes next.
Regards, Peter.

 

[Blogwitch]

Lovely piece of work there Peter, keep it up.

As I told you before, lathe not required, just a decent method of hold down on the RT.

The hard bit is now done so you can start to machine the hub, spokes and rim for the full effect.

Well done.

John

 

[Cymro77]

Peter,
An incredible piece of work. I am faced with a similar situation on a smaller scale. The rotary table is my nemesis!
Thanks for sharing your ongoing build.

 

[deeferdog]

I would like to say that from here on in all was plain sailing, but of course it wasn't. The mistake I made was to cut out the pieces of pie by going around using the RT. The trouble with this method is that the two opposing spokes are not done at the same time. A much more accurate method would be to cut the curved top of the pie section on the RT, then remove the blank and locate on the mill table and cut the spokes using the X axis. I ended up having to do this as each spoke was slightly different from its opposite number. This error was undoubtedly due to me but the backlash in my RT didn't help, at 4 inches it's a bit small for such a big job. Anyway, I faced the spokes down 6mm leaving a 65mm hub which I radiused using a rounding tool. I did the internal of the rim in the same manner. After doing the other side, I then removed the wheel from the RT and clamped the wheel to the milling table. I bolted two stops to the table such that they were a snug fit against the internal of the rim and the spoke. I dialed the wheel in along the x axis and clamped down. The advantage of this was when it came time to do the next two spokes it was just a matter of un-clamping the wheel and rotating to the next set, the centre remained exact so all the numbers on the DRO were correct. I recut all the spokes to within .002", plus put stopped chamfers on them, all in about two hours. Both sides! I was pretty pleased. This is a much more accurate and easy way of doing the spokes than on the RT, at least I found it so. After a bit of a rub here and there with wet and dry, I thought it came up reasonably well for a first effort. I could do it better next time, but that is generally the case. For heavy cutting, the ruffer was the bees knees and skimming half a mil or so off with the finisher sure makes the clean up a lot easier. I think I've earned tonights scotch.
Cheers, Peter

 

[ShopShoe]

I knew you'd get it. I like to say that the real learning comes from working with what you've got, not with what you bought.

How it looks -- It looks great. You've demonstrated the machining but I'd like to say that I can say kudos for the design as well.

Looking forward to what you do next.

--ShopShoe

 

[Blogwitch]

Well, you really got that under your belt now Peter. There should be nothing holding you back now.

You can now say that you have tried it and succeeded with flying colours.

Have a look at my signature line below.

Great work.

John

 

[bazmak]

I a very impressed a job well done.Following with interest

 

[deeferdog]

Thanks, I think your comments flatter me but I love them all the same.
Regards, Peter

 

[deeferdog]

I have to confess that I don't have any step by step plan for building this engine, things just seem to flow. I decided to do the flywheel because I could see that it was a big hurdle that would have to be overcome if the machine was to be completed. However, now that this has been accomplished it merely shows that the next hurdle is how to connect it to the engine. The drawings simply show everything from the base up, neglecting the fact that the flywheel is 300mm (12") and half of it hangs below the base. So unless I resign myself to always running the engine on the edge of a table or such, it is going to need an elevated base. Also, this base is going to have to somehow offer support for the other side of the flywheel bearing which is another thing the drawings omit. Sigh! After looking through pictures of beam engines on the internet, I decided to have an open arrangement rather than a box and based on this decision, off I went. I had some 30mm (1.18") brass tube and cut four 120mm (4.72") columns. The top and bottom of the columns would need some adornment, I decided to use aluminium and bright polish them. The model is intended to be painted at the finish so these should add a bit of brightwork. The pictures tell the story better than I can describe. The set of rounding tools I brought from Hong Kong are very good. I made a holder and bushes for them to use on the lathe toolpost. Because the cutting edge faces down, I run the lathe in reverse and feed in, lovely and no chatter. The top pieces were cut from 50mm (2") round, the bases from 50mm square. I used 10mm (.39") threaded rod screwed into the 12mm (.5") aluminium base, then the column base was slipped over the rod and retained with a nut and washer. The brass column, with its top attached (Locktite) spigotted into this, the engine bed over the threaded rod and onto the columns and the whole put under compression using four nuts, these will be replaced with something a bit more glamorous at a later date. All in all, not too bad. Next is the outer bearing support. I'll have to have a think about that. Cheers, Peter.