Author Topic: Mystery engine  (Read 4053 times)

Offline Jasonb

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Re: Mystery engine
« Reply #15 on: September 27, 2020, 12:11:13 PM »
So what's the thinking on the induction side of things?

Did the flat flange with a bit of soft solder on it connect to the gas supply and draw in a small amount of gas with the air coming in via the top mounted valve on the cylinder or did air and gas enter into the flange through a missing part much like the Sphinx with the exhaust going up out of the vertical spigot.

The two inlet valve springs look quite thick for atmospheric opening but may be OK.

J

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Re: Mystery engine
« Reply #16 on: September 27, 2020, 01:36:24 PM »
Hi Jason.

Your guess is as good as mine. Ray did point out that the previous owner had done some minor restoration, the heavy spring on the inlet would not work atmospherically. So with perhaps a positive pressure of gas on that valve and the top acting as air only might work.

If it were me I'd opt for a " Sphinx like " arrangement and totally ignore the top valve altogether.

I'm guessing readers can see the close similarities to the R.L.E. ? They should because it was my own engine, pictured below that was the inspiration.

I've worked on many of the larger HP Leek engines over the years, one feature was the reduced diameter of the crankshaft inside the main bearings. Reduce end float ??  :)

Cheers Graham.

Offline RayW

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Re: Mystery engine
« Reply #17 on: September 27, 2020, 02:47:48 PM »
The previous owner did point out that a lighter inlet valve spring would be needed and the atmospheric valve also needs one as well. My preference would be to leave the gas and air inlets separate initially to see how well that works.

I have my doubts as to how effective the water jacket would have been as there seems to be very little clearance inside, particularly if the cylinder retains its fins as I suspect. It will also need a proper threaded connector soldered on underneath as there is just a small hole and a rough patch of solder at the moment.
Judging by the wear on the gears, which are 32 to 16 ratio, the engine has done a lot of work in the past.

Ray

Offline RayW

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Re: Mystery engine
« Reply #18 on: September 29, 2020, 05:39:54 PM »
Been having a closer look at the engine today. I had assumed that the spindle for the large gear was badly worn as the gear was wobbling about. On closer inspection, I discovered that the locking nut for the shaft, inside the bracket bolted to the engine bed, was very loose. On tightening it up, the gear now runs true with no wobble.
I had concerns that should I decide to replace the badly worn gears, I might have trouble removing the flywheel to access the smaller gear,  but to my delight, on undoing the locking grub screw, the flywheel slid off the crankshaft easily.
There is quite a wobble on both flywheels, but this seems to be worse when the grub screw in each flywheel hub is tightened, indicating that the flywheel bore may be worn, allowing it to tilt slightly when the screw is tightened. I will have to have a think about the best way to sort this out. I could either plug and re-bore the flywheel or add another grub screw to the opposite side to counter the tilt. Either way, I would want to do the modification as unobtrusively as possible. The flywheels have been re-painted in the past so should not be a problem to blend in any repairs.
« Last Edit: September 29, 2020, 06:00:29 PM by RayW »
Ray

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Re: Mystery engine
« Reply #19 on: September 29, 2020, 09:28:33 PM »
Hi Ray.

Whilst the grubscrews would have been more than adequate to secure the flywheels for an atmospheric operation I feel they would work loose very quickly under the present situation.

I personally would make a replacement crankshaft and put in keyways. You can then keep the original crankshaft for posterity.

My own engine had its shafts threaded to 3/8" BSW and the flywheels were literally clamped between two nuts. ( common practice for the home machinists of the time ) My good friend Martin replaced them with plain shafts and keyways. We used the original crankshaft on this occasion as we didn't think anyone would like to see threads!

At the end of the day the choice is yours and what you do will depend upon how you're going to use the engine. A simple solution would be the use of thin Steel shim to " pack out " the discrepancy.

Cheers Graham.

Offline RayW

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Re: Mystery engine
« Reply #20 on: September 30, 2020, 10:24:32 AM »
Hi Graham,
I am reluctant to replace any more parts than necessary for now, to retain its lovely aged look. As far as I have been able to see, the bearing surfaces and crank journals, and the areas under the flywheels all remain in pretty good condition, even though the webs and exposed areas are pitted. The same applies to the exhaust valve operating bar which is heavily pitted, except where it passes through the two brass guide brackets.
Even the gears, which are heavily worn still run OK, with the missing tooth on the crank gear seemingly not making any difference.

The first job I need to tackle is the three valves (exhaust, gas inlet and air inlet). All need re-seating to try and get some compression. When I turn the engine over, there is plenty of air blowing out from various places so it looks as if the new piston is a good fit in the cylinder, even though it has no rings.
Ray

Offline RayW

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Re: Mystery engine
« Reply #21 on: November 08, 2020, 04:14:56 PM »
The attached article, which is reproduced by kind permission of Patrick Knight, the Editor, has appeared in the December 2020 issue of Stationary magazine.
Ray

Offline RayW

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Re: Mystery engine
« Reply #22 on: January 27, 2021, 12:37:49 PM »
Tried some much lighter springs on the gas and air inlet valves but little compression, although there is a little suction through the gas valve and a light puff of air from the exhaust valve.

Having dismantled the valve chest, it is clear that I am going to have to make completely new valves and fit new valve seats. As can be seen from the photos, the exhaust valve seat (on the right in photo1) is a very off-centre copper plug. The exhaust valve (seen below) is very crude and badly corroded. For some strange reason, the section below the head has been filed to a triangular section. The inlet valve chest (on the left in photo 1) also has an inset copper plug and, again, the valve is badly corroded and such a loose fit in the valve guide that it just wobbles about. It is also slightly bent at the head end. It looks possible that these crude valves may have been made from bolts or screws as they have quite deep slotted domed heads.

As will be seen from photo 2, the atmospheric air inlet valve, which sits on top of the cylinder, is also very crudely made and is unlikely to work properly, so a replacement will need to be made.

The hot tube, which I suspect was never fitted to the engine when it was running as it show no signs of ever having been heated, is fitted into a removable boss, which is screwed into the cylinder head. I spent a considerable time trying to identify the thread in the cylinder head which is the same as that where the valve chest screws into the cylinder. I established that it was 3/8" x 26 TPI but couldn't find that thread listed in my charts, until I discovered a tap in my "Miscellaneous Taps" box marked B.S.A 3/8" x 26 TPI B.S.B, or British Standard Brass. I am hoping that I will be able to open the cylinder head thread out to M10 x 1 to take a standard CM6 plug.

The other two photos show the inside of the cylinder head and the piston in the cylinder. The piston is the only new part made by the person that I bought the engine from.



Ray

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Re: Mystery engine
« Reply #23 on: January 30, 2021, 12:09:18 PM »
Hi Ray.

My own engine appeared to have had " converted " fixings for the valves too, where possible I left them in situ.

You're not alone..... Yet another engine has come to light in almost " as found " condition. Driving an EEC dynamo. Few today would realise that they were needed to keep Radio batteries charged for the valve/tube heater circuit.

Cheers Graham.

Offline RayW

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Re: Mystery engine
« Reply #24 on: January 30, 2021, 04:39:14 PM »
That's rather nice. Where did that one appear from?
Ray

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Re: Mystery engine
« Reply #25 on: January 30, 2021, 07:25:56 PM »
That's rather nice. Where did that one appear from?

Hi Ray.

Yet another " eBay " discovery....

 :cheers:

Offline RayW

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Re: Mystery engine
« Reply #26 on: January 30, 2021, 09:10:42 PM »
Yours now?
Ray

Offline RayW

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Re: Mystery engine
« Reply #27 on: January 31, 2021, 05:37:28 PM »
The inlet and exhaust valves were in such poor condition that I made completely new ones and re-cut the valve seats. Both now seem to be sealing OK but still almost no compression, so the inlet valve is not being sucked open, even though I have fitted a much lighter spring..
Made a cylinder head gasket and one between the two halves of the valve chest today and those areas now seem air tight. There is still no compression, however, as the air valve on top of the cylinder is leaking badly, and is so crudely made that the only option seems to be to make a replacement. The one big problem I have is that I have been unable to identify the thread where it screws into the cylinder. The OD of the thread on the valve is 0.295" and the pitch appears to be 20TPI. I have searched the internet, but cannot find anything that matches this.
If I can't identify it, the only option will be to cut off the thread from the valve and solder it to the new one.

I have now re-tapped the thread in the cylinder head where the hot tube was fitted to accept a standard CM6 spark plug.
Ray

Offline RayW

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Re: Mystery engine
« Reply #28 on: February 05, 2021, 12:29:23 PM »
After a bit more work on the valves. I managed to get pretty good compression, with the gas and air inlet valves both opening and closing under suction.

Decided to pull out the crankshaft today to see if it was salvageable and just as well that I did, as I found that one web was twisting slightly on the main journal. As can be seen from the attached photos, all of the bearing surfaces are in pretty poor condition with lots of pitting. The webs are also heavily pitted all over, although a lot of the pitting is not too deep.

The crank is of made-up construction, with two separate main shafts, each being either press fitted, or soldered into its respective web. The ends of each shaft are reduced to a similar diameter to the main journal where they pass through the web. It is unclear whether the collars adjacent to each web are part of the shafts, or part of the webs themselves.

One thing that puzzles me, as with the rest of the engine, is the odd mixture of dimensions, which do not seem to comply with any fractional or metric ones, with a few exceptions. Bearing in mind that this is an early English engine, one would expect most to be fractional, but, for example, the main bearing diameter is 0.349" which falls between 11/32" and 23/64". The webs are 0.230" thick which, again, does not correspond with any standard thickness material.

As far as I can see, I have two options;

1) Make a completely new Crank, copying the existing counterbalanced design, but using standard size materials, eg 3/8" diameter shaft and 1/4" thick webs and adding keyways to the shaft and flywheels, which are currently retained only by a locking screw.

2) Try to dismantle the existing crank and re-use the webs, re-boring them and just cleaning up the worst of the surface pitting, but leaving evidence of their age.

Ray

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Re: Mystery engine
« Reply #29 on: February 05, 2021, 01:34:29 PM »
Hi Ray.

I made the suggestion of replacing the crankshaft a few posts ago and still stand by it. Rather than perhaps destroy its history you can keep hold of the original and make a decent replacement for running.

With regard to the " odd measurements " well.... I do the same, make one part fit the next.   ;)   It seems to have been common practice back in the day of small power engine building.

Regarding that latest engine find, no not mine but a member of the FB group. So that's the third one I've seen now !

Cheers Graham.