Author Topic: Building the I F Allman from Alyn Foundry  (Read 953 times)

Offline Jasonb

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Building the I F Allman from Alyn Foundry
« on: May 19, 2019, 06:33:57 PM »
Some of you may have been following the other thread about this engine here which goes into some of the history and design decisions but I thought I would do a separate build thread now that the engine runs.

As I had no drawings to work to I had to jump about from one part to another so that they could be used to work out what positions and fits were needed but I will try and post each part in order as the other builders with a nice set of clean drawings will be able to work in a more ordered fashion.

The first and most logical part to start with was the cast base plate which at just over 8" square and 1/2" think is quite substantial. After a quick cleanup of the casting and studying the heights of the projections I set it up on the mill to skim the underside using various bits of packing so that when machining the top these projections would be an average of 1/8" above the surface after face milling.



The four bosses for the hold down bolts in the corner as shallower so they were individually skimmed until the surface just cleaned up and a simple bush and transfer punch used to locate holes centrally.



A bit of fiddling about and taking of measurements later and the best position for the cylinder and A frames was found so that the 16 5BA and 4 3BA holes could be drilled and tapped. Other builders can add the M3 and M4 clearance holes at this stage for the rocker arm pivots and gas control but I did these at a later stage as other parts were made and their positions worked out.




I started off machining the feet of the A frames using a cheap Bangood facemill which after correcting the excessive runout and fitting some decent tips seemed to be cutting well, however when I went to stand the frames upright they had a lean to them. Further investigation showed that the inserts were not being held at the correct angle and the sides were running rather than having slight clearance.



A change to my trusty 3 tip cutter and a different setup had the feet good and square.



And the tops parallel to the feet.



The only downside to this was that I ended up 1/64" short of the 7 1/16" I was aiming for ( later recovered by adjusting the bearing housing height)



Holes are added to the feet for 5BA studs



The tops can be drilled and tapped for the bearings. Once the bearings are fitted they can be scribed around and the top of the frames milled back to the lines.





The large timing gear needs a counterbore machining into the inner face of the a frame, it's centre best located by using teh gears to determine the exact position of the threaded hole for it's pivot post.










Offline Chipmaster

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Re: Building the I F Allman from Alyn Foundry
« Reply #1 on: May 22, 2019, 09:01:36 AM »
Hi Jason, ill start work on my Allman castings now, thanks for sharing your drawings and methods.
Andy

Offline Jasonb

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Re: Building the I F Allman from Alyn Foundry
« Reply #2 on: May 24, 2019, 08:14:44 PM »
The cylinder casting can be held in the 4-jaw chuck to have the bottom face machined starting with facing the bottom then a light skim off the off of the flange OD. Then bored for the liner and a small recess added for the liner's lip.



I deviated from graham's original and decided to have an enclosed water jacket as shown on the patent drawing, to this end a recess is cut into the top of the casting to take a collar and the first internal web is turned away. A light skim off the very top can be taken at this time, just enough to tidy up what will be a painted "cast" surface on the finished engine.



This drawing shows what the modified casting now looks like in section



And the three waterspaces that will be created when the top collar is added.



To link these three horizontal bands vertically a boring head was used to make some concave passages but making sure there was plenty of metal left to form a good seal between jacket and liner where the inlet and two exhausts pass through.



The blue cross was where the upper cast ring had been machined away, liner part way into the casting. Also make sure there is no core sand left in this casting before you spread it over your lathe ways, mine had a few bit still caked on.



Having decided on an enclosed water jacket there is a need to get water to and from it, I used a couple of milling cutters to cut the 5/16" through holes due to the curved surface then a 7/16" one to counterbore almost all the way through. Some 7/16" bosses were drilled and threaded M8 x 1.0 and bonded into the holes with JBWeld. 5/16 x 26 or 32tpi could be used if you are still in the old world.



With the cylinder stood on it's end and clamped between a pair of angle plates the four 3BA clearance holes were drilled along with the six M3 tapped holes for the cylinder head. I have opted for metric fixings anywhere they don't show as they are cheap and socket heads can be used. Would have liked them an a slightly larger PCD but there is not enough metal on the head to allow this.



Using a couple of drill bits in the 3BA holes the casting can then be indexed around to machine the two valve faces and tap the primary exhaust hole.





« Last Edit: May 24, 2019, 08:20:36 PM by Jasonb »

Offline Admiral_dk

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Re: Building the I F Allman from Alyn Foundry
« Reply #3 on: May 24, 2019, 08:21:49 PM »
I like your solution Jason - nice work as always from you  :praise2:

Offline Jasonb

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Re: Building the I F Allman from Alyn Foundry
« Reply #4 on: May 24, 2019, 08:57:38 PM »
Thanks Admiral.

The liner was not an ideal casting with some pattern shift but the cored hole was reasonably straight so I used that to set things up. No photo of the first setup which was to hold in the 4-jaw by the small diameter to face the flange and turn the edge round and concentric to the cast bore.



I then glued a plug into the other end and held by the flange to turn the outside diameter and the small 1/16" lip but leaving as much of the cast flange as possible as this prevents the liner distorting under the pressure from the jaws. luckily the casting is over length and I just managed to end up with a clean surface within the pen mark which indicates the final length.



Now having a smooth outer surface the fixed steady can be used to support the liner first to machine it to length ( leave 20thou over at this stage) which keeps tool projection to the minimum when the liner is then bored.



The last job is to hold lightly by the outside to turn away the unwanted flange just leaving the lip, luckily the liner just went into the bore of my 4-jaw so there was not too much overhang.



The collar to close of the water jacket is a simple turning job from as stub of cast iron bar that can then be parted off.





The liner and ring can now be fitted to the jacket with 642 Loctite, I also added a drop through each of the water bosses and moved the assembly about so it flowed into any missed joints before sealing up and allowing to go off. Once set the cylinder can be held in the lathe and a finish cut taken along the sloping collar and liner end so the joint becomes invisible, finally ease the liner edge so the piston ring slips in easily. Final holes for inlet and exhausts can also be added at this stage.




Offline Jasonb

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Re: Building the I F Allman from Alyn Foundry
« Reply #5 on: May 26, 2019, 06:47:50 PM »
With the liner now made that can be used to gauge the size of the cylinder hear which is first held by the smaller diameter to face off the flange and clean up the OD.



I then used soft jaws to hold the flange for the remaining turning, the thin edge of the Hemi head was quite hard as can be seen by the brighter finish which shows up even more when rotating but a CCGT tip managed to cut it Ok.





All that remained was to add the six 3.0mm holes and clean up the concave surface with a grinding bit in the Dremel



The piston is fairly straight forward just consisting of turning and boring though a hard lip did slow things down. Then over to the mill to open out the space for the little end and drill & ream for the pin.



I left my ring grooves until later while sizes were worked out but other builders can turn these at the same time then add the couple of milled notches that ensure the inlet and exhaust ports are not blocked.

Offline Jasonb

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Re: Building the I F Allman from Alyn Foundry
« Reply #6 on: June 02, 2019, 07:26:16 PM »
The castings for the inlet and exhaust valves were not the cleanest with several areas of excess iron where the sand had broken away from the mould.



So first job was to clean them up with files and die grinder and then establish a flat surface, while doing this the ctr was found and the two 5BA clearance holes for the fixing studs added





With that done they could be fixed to the cylinder and the bosses and flange fettled to give a pleasing joint of matching shape.





Where ever possible I like to machine the valve seat on the lathe rather than using a CSK or valve seat cutter as it keeps things concentric and I don't seem to suffer from leaky valve or have to do much in the way of valve grinding so the exhaust casting was set up in the lathe to ream for the valve, counter bore behind the valve, machine the 45deg seat and do the second counter bore all in one setting.



Then over to the mill to do the hole for the exhaust stack, I felt 1/4" BSP would be a bit close to the edge of the casting so opted for M12 x 1 though 1/2" x 26 or 32 would also do. The spiral flute taps make easy work of it and their short lead in taper means you can tap to almost the bottom of a hole that a taper tap would hardly start in thus making it hard to follow up with 2nd and plug taps.



Final op on the casting is to push it onto a mandrel so the end where the spring goes can have a step machined onto it to locate the spring.

The valve is straight forward turning from Stainless steel, L leave them on the bar stock to grind them in with 600g SiC then cut off and finish the head. I did use ctr support to turn it, the resulting hole is easily turned off by poking the valve into a collet from the back.



The exhaust stack is just turned from 303 stainless bar with a decorative bead on the top, spring collet is simple turning job, spring came from my box of tricks springs. Assembled on the engine



And unassembled.



J



« Last Edit: June 02, 2019, 07:29:22 PM by Jasonb »

Offline Jasonb

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Re: Building the I F Allman from Alyn Foundry
« Reply #7 on: June 23, 2019, 06:58:12 PM »
The inlet valve block is a bit trickier as it has a couple of passages drilled at an angle and a small one for the gas that has to break out within the valve seat so that can close off the gas supply.



Starting with the top facing out of the 4-jaw after cleaning up cuts to the top face the main cavity was bored & tapped, cavity behind the vavle drilled, valve hole drilled and reamed and finally the valve seat turned with the top slide set over to 45degrees.



The hole for the air is quite straight forward  as are the two studs for the inlet elbow and the 1/4 x 40 threaded hole for the gas pipe. Things get a bit more interesting with the small hole for the gas which needed an extension so that the drill could reach down far enough to the valve seat and it is not easy to see what you are doing.



View through the gas pipe hole.



And where the hole enters on the valve seat



The top cover is fairly straight forward turning from brass, I used a ctr drill to put a small 60deg seating for the hot tube to seal against which seems to have worked well with a touch of Graphite Foliac. The hot tube itself is simple turning from stainless steel, just make sure the 1/8" drill does not wander as it's a long hole, I started it with a stub drill.



For the inlet elbow I chopped up an 8mm Yorkshire plumbing elbow and silver soldered that to a scrap of brass as it's easier than trying to get a tight bend from pipe.

The valve and cotter are simple enough from stainless steel with a light spring, just enough to close it but not too much as you want the vacuum of the rising piston to open the valve.

I decided not to use the cast chimney instead turning a stainless steel tube with a decorative bead on the top, this was silver soldered to a bit of steel to form the bracket that was shaped, drilled to fit the vertical support rod and cross drilled and tapped for a 5BA lock screw. The casting will machine up much the same way and can be drilled 11mm for a Sievert burner if you want to use that rather than the ring burner shown





Offline Chipmaster

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Re: Building the I F Allman from Alyn Foundry
« Reply #8 on: June 23, 2019, 07:27:13 PM »
Excellent work Jason, easy to follow. Im only making slow progress with mine, Ive worked on the main bearing housings this afternoon.

Andy