Mill Engine

[John Antliff]

As long as you do the radiusing using conventional milling and NOT CLIMB milling you should be able to control the job without any grab taking place. Do it the wrong way and you will result in driving the job around the pivot with most likely a broken end mill and seriously dented pride! The hole and pivot need to be intimate i.e. no slack.

 

[deeferdog]

I have to admit that when I did the radiusing I didn't think too much about it grabbing. I worked carefully, conventionally milling and only took small cuts. After reading what Cogsy has said about his experiences I can sure see the sense in setting up stops. I guess the similarity is holding a piece of steel in the drill press and wondering if its going to grab. It's only after it has, and nearly broken your hand, that you start to think that clampling it first might have been a good idea. Thanks for all the comments, Cheers, Peter

 

[deeferdog]

On to the stuffing box which, as everyone knows, is a very old fashioned device for preventing steam pressure from escaping out of the cylinder around the piston rod. All the machining was brass, a metal that is lovely to turn but terrible to clean up after, the chips get right into the guts of the lathe! Enough whinging, fairly straight forward job, slightly changed the dimensions to suit what stock I had on hand. As an example , the plans call for a finished size of 52 mm and I only had a piece of 50 mm round bar so 50 mm finished it became. It doesn't fit into anything so no problems. The stuffing box cap was made from the same bar and the the six holes drilled using the RT. The box itself is attached to the cylinder with four screws from the inside, everything secured with Loctite. Finished off the day by replacing the washers in the shower taps even though I know they will only last a couple of months as the tap seats are absolutely shot, what a bugger of a job that is going to be to fix. Advance to the piston tomorrow. Cheers, Peter.

 

[Cogsy]

Finished off the day by replacing the washers in the shower taps even though I know they will only last a couple of months as the tap seats are absolutely shot, what a bugger of a job that is going to be to fix.

Peter, if the taps seats are too chopped up to use one of those cheap seat recutters you can buy from Bunnings, and they're set into the wall and hard to change, there is another easy solution. About 10 years ago I went to a plumbing supplier (Reece's Plumbing over here in WA) and bought a kit to repair damaged seats. It's basically a tool which screws into where the tap normally does, and it bores the throat of the seat to the correct size, then taps the bore of the seat. You then remove the tool and screw in one of the supplied stainless steel seats into the new thread and reinstall your tap with a new washer. From memory the kit cost me around $60-$70 but it's far cheaper, and simpler, than masonry work.

Engine is looking great by the way!

 

[deeferdog]

Thanks Cogsy. I've been warned that the re-cutters sold by Bunnings can do more damage than good. I didn't realize there was a better quality alternative available so I'll pay Reece a visit, possibly after I do the retaining wall. Does it ever end? Thanks for your interest, Cheers, Peter

 

[deeferdog]

At last the piston, and at 76 mm diameter it was going to be a bit of a beast, I had a piece of cored bronze that was 80 mm so I decided to use that and put an aluminium centre in. The bronze was beautiful to turn and the centre was made as a press fit and once again pushed in with good old Loctite 263. Possibly the purists will be aghast at this mix in metals for the piston due to the dissimilar expansion rates but this will be basically a static model that will only ever be run on air so I think it will be OK. It's all I've got anyway. I cut a groove for an O ring, bored and tapped the centre M12 and threaded a piece of 12mm bright bar for the connecting rod. This too was Loctited into the thread in the piston. For once I got a lovely fit, slides up and down the cylinder and makes puff puff sounds, I think it will run OK without an O ring should I decide to go that way, we'll see. Some pictures and then on to the valve chest. Cheers, Peter.

 

[retailer]

Looks like it is full steam ahead for you on this one - it's coming together nicely.

On the subject of the bathroom taps - if you go the route of tap seat inserts then do not use the nylon washers supplied with the kit for the hot tap, hot water flowing through the tap causes the washer to soften and compress and it will soon start to leak, use a fibre washer instead.

 

[deeferdog]

Thanks retailer, I'm rapidly becoming an expert in tap washers, the variety is mind boggling, all of which have proven useless. So, on to things at which I have had more success, steam engines. As I mentioned in the previous post, the steam chest must now be addressed. This part of the model is the most complex as the chest is comprised of six separate parts. The first, the gallery block fits against the cylinder over the upper and lower inlet holes and becomes the manifold to distribute the incoming and exhausting steam. I cut the block from a larger piece of aluminium with the slitter and machined the various faces as per the drawings. The holes were drilled mostly in the correct places, mistakes were made but were able to be corrected. The two end holes that are necessary for the inlets to be connected, simply plugged and machined off rather than tapping and fitting a screwed plug, this made the whole thing a bit simpler. Probably I spent more time figuring out the drawings than in the making of the piece. The plans are good and well drawn but some of the views are confusing, however I am easily confused. Pictures as always to assist in understanding this convoluted text, to those who are still with me on this build I not only thank you but also salute your endurance. Finish off the chest in my next post, Cheers, Peter.

 

[deeferdog]

The completion of the steam chest was reasonably straightforward necessitating the making of three sides and the top and bottom. Some close fitting is required here and hand finishing with a file was needed to make the parts look the part. A broken tap didn't help, M5 and it broke on withdrawal, always the worst case in my opinion. I messed around with it in the usual fashion in the forlorn hope that I might be able to extract the stump but this ain't the movies so in the end I just ground it flat and left it be. The lid will feature a fake screw in that location. (That should trigger a bit of muttering.) When it was all finished and fitted it looked remarkably close to what the designer had drawn, which is not always the case with my work. Pictures submitted as usual. I am looking next at the slide valve made from a solid lump of brass. The designer must have a lot more money than I have so that will have to be changed. I'll show how in the next post, Cheers, Peter.

 

[johnmcc69]

I'd say it looks like things are moving right along peter, nice work.

John

 

[deeferdog]

Thanks for the comment John. On to the vexed topic of the slide valve. I say vexed because the finished external dimensions of this piece are 52 x 32 x 30 mm which is a fair lump of brass and where I live, brass is difficult to buy and expensive plus I promised that this engine would be made largely with what I had on hand. I decided to make the slide from aluminium and fit a brass "shoe" on the face that slides against the gallery block. I fastened the shoe to the valve using four bronze dowels, pressed and Loctited into the aluminium block, then faced off. The dowels were small pieces nipped from the end of a bronze welding rod. The whole of the slide was then finished as per the drawings. The valve stuffing box I made as a smaller version of the cylinder one which was a departure from the plans but I thought it looked better, and I used 8 mm bright bar for the slide valve connecting rod. Everything came together in various levels of harmony when I did a test assembly. Good. Later I will do the permanent fitting of the valve chest to the cylinder and make any adjustments as necessary. My adjusting tool of choice is a hammer. More pics, have a good day to all who are reading this, Cheers, Peter.

 

[champ2run]

I am thoroughly enjoying your skill and ingenuity. Impressive to say the least. Looking forward to the run. Ted.

 

[deeferdog]

Thanks for the praise Ted, thoroughly undeserved but I love it anyway. The engine by now had passed the half way point and some decisions need to be made concerning the painting, even though this will take place when the model is finished. Some parts can be described as a sub assembly and painted as such without being disassembled, the cylinder-valve chest being one case in question. I decided to fully put this together in a permanent manner and the first job was to locate the gallery block to the cylinder. This is secured by four M5 socket head screws but I think it needs more than that. I epoxied it to the cylinder using the Chinese Araldite rip off from Banggood. (Excellent results, less than one third the price.) The sides and bottom were assembled using Cyberbond flange sealant. I have had good success with this product, unfortunately it is expensive and is sold in great big tubes with hardly anything in it which does nothing to generate warm feelings toward the company. At this point I checked the other parts of the engine, mainly for fit and accuracy when assembled. The slight curve in the base plate was causing a few deviations that I knew would cause the machine to run tight, so I stiffened the underside with two steel bars under the crosshead and a full steel plate under the main bearings of the crankshaft, this all helped but the final analysis will have to wait until the first run. Next will be the eccentric for the slide valve, my dear wife would say that I was the perfect person to make eccentrics but I won't enter into that. Pictures to make all this clearer, Cheers, Peter.

 

[peter2uat]

I've read that you can remove broken steel screws/taps with a stiff & hot Potassium alum [KAl(SO4)2] solution which will eat away the steel and leave the aluminum intact. That's the crystals we use as Deo sticks or to desinfect/stop bleeding small wounds (after shaving) and may be found as "alum powder" in the spice section of grocery stores for pickling veggies/fruits. Drug stores/pharmacies could be another source.
Peter

 

[peter2uat]

There is some similar and much cheaper product - Loctite RTV Red at $ 5 for 80ml which has the added benefit of being heat resistant too.

 

[deeferdog]

Thanks for the tips Peter, I'll try the Loctite when the Cyberbond is finished. The making of the eccentric wasn't my finest hour. The drawings advocate making it in two parts, the outer flange being a separate item that is attached with a fastening. This method allows the eccentric ring to be made as one piece and just slipped on I decided to stick with the way I had made them before, that is as one piece with a split eccentric ring. The ring making went OK but the actual eccentric was a pigs ear. I miscalculated the offset, never a good start, and after an hour or so of clunk clunk clunk offset turning ended up with an eccentric shaped piece of scrap. I just couldn't face the prospect of doing the same thing again, so the second time around I set the roundstock up in the mill and bored the shaft hole the offset distance from centre, then turned the hub in the lathe and soldered it to the eccentric. How's that for cheating! Actually, it turned out so well that all future eccentrics made be will be done this way. Only thing left to make is the valve rod end and the valve guide, I'll do that in the next post. Thanks for reading, Cheers, Peter.

 

[deeferdog]

The final parts of the engine are now starting to come together. The eccentric coupling was a smaller version of the connecting rod one and for the intermediate bearing I used one of the posts I made for the discarded version of the crosshead. Setting up the eccentric involved making sure the slide valve uncovered each port equally in its travel, then the steam chest cover was buttered up and screwed down. For the piston ring I used an O ring. It was too large so I shortened it until both ends just touched when fully home in the groove. Buttered up and attached the head. Added inlet fittings, connected air and after a bit of adjusting of the eccentric position on the crankshaft the engine snorted and came to life, albeit briefly. Quite pleased. Now to pull it all to bits for the painting, lagging the cylinder and tweaking the assembly. All that in the next post, how exciting. Cheers, Peter.

 

[deeferdog]

Here is the link to the first run of the mill engine. . Cheers Peter

 

[Picko]

I'm following Peter. Nice work and photos, and runs nicely too.

Cheers John

 

[deeferdog]

Still a bit tight John, will be better after tweaking which I will do after the painting. The whole engine was disassembled down to the main sub assemblies and washed in hot water and detergent. The hole in the flywheel (needed to access the grub bolt when it was a transmission pulley) was filled with bog and ground down. After a coat of primer I applied three coats of Brunswick Green to the engine and base and Heritage Red to the flywheel. I just use spray cans and I'm no expert but I was happy with the result. After the paint had cured most of the fastenings were replaced with stainless steel as I don't like my nuts and bolts painted. I reassembled everything and paid a lot of attention to alignment and fits, I think it will run much smoother when I fire it up again, which I will in the next and final post of this Mill engine. Only the teak lagging to fix to the cylinder and a bit of brass bling to go. Onward and upward, Cheers, Peter.