In a departure from my usual practice of not posting a build thread until an engine has at least been test run I'm going to make an exception with this one. Graham Corry of Alyn Foundry & Sons has announced this week that there will be a new batch of castings being done for his popular "RLE" design of hit and miss engines. For those that don't follow Alyn's Facebook page and who may want to secure a casting set then make contact via this e-mail address and you can check the price and place your deposit. alynfoundry103@gmail.com. Hopefully most of this thread should be complete and act as a guide to anyone who decides to order an RLE.

I got most of a set of castings for this engine a couple of months ago which Graham managed to cobble together from his last few remaining castings with the exception of the flywheels which will be getting cast along with the new batch of kits so that will likely make this the last supplied with castings from the old foundry and no doubt rammed up by Graham himself.

This will also be the first engine to be built to a new set of drawings as the original set leave a bit to be desired in this day and age. They will also be in metric which will hopefully attract some of the newcomers into the hobby who have been brought up with the metric system and have tooling and machines based on that system rather than Bananas.

The new drawings set will also take into account the newer carb design and show modified rocker arm, rocker bracket, cam and head details to suit it's straight vertical pipe entry. It will show the MOD gears, metric fixings, O ring for the piston and a fuel tank (No Baccy tins from now on) as well as optional square push rod and governor balance weight designs. Lastly there will be details of a cart with hopefully the addition of cast cart wheels and axle brackets and a spoke mounted pulley casting that will be available as extras.

I have been modelling the engine as work progresses making adjustments to suit how the castings machine up as I go, this is the state of play so far.

That's enough of the intro, time for some swarf 

Starting with the base casting after a light fettling it was shimmed up on the mill table to get the sides tapering equally and the bottom flange milled flat using an insert facemill. While still held in position by the two clamps on the inside a round disc was held in the mill spindle to help best locate the centre of the two cast bosses.

After spotting and drilling for the hold down holes I ran around the edge to just clean up the flange so it was straight enough to use as a reference surface, you may also be able to see that I have milled the internal fillets to the left boss stopping at a scribed line that was done around the disc at the time of locating it which can be used as a guide to trim the bosses to a more attractive shape.

Now that the base had a flat bottom it could be clamped to the mill table, the skimmed flange edge set true and the upper surface machined again with the facemill. You may notice I am using polished inserts intended for aluminium and non ferrous on this cast iron part as I find the sharper inserts put a lot less strain on the lower powered and less rigid benchtop mills than the standard inserts do. The carbide will also cope a lot better should there be any hard areas in the castings which was not a problem with these specially coated Welsh products.

I left out drilling and tapping the four holes to mount the crankcase until I had machined that but they could be put in now working to the sizes on the new drawing. A bit more fettling of the surfaces and clean up of the corners was done as well as spot facing the two mounting bosses before moving on to the next part.

Edited By JasonB on 22/07/2023 19:30:02

Thanks for the interest

I suppose they are lucky that the RLE was their most popular design and easily outsold the other engines before health and foundry problems caused production to stop. So the market was there and still is, infact there has been a steady demand over the last few years for very small batches of other engines and now that the missing RLE working patterns have been replaced this one is available again.

I don't think they will be making enough to retire yet but run as Graham used to as a complement to a proper job it will be a steady bit of extra income

The old web site is in need of an update, those shown in the "coming soon" arrived over 20years ago. Though the Hornsby could not be got to run well enough to be offered for sale and so far the IF Allman ha sonly had 3 sets of castings done buy borrowing the patterns and getting the casting done ourselves but it is one that hopefully will become available in the not too distant future and is a nice engine.

The e-mail on the website should still work but better to use the one I posted or contact Graham through Alyn's Facebook page

My Alyn I F Allman engine

It's the next engine I'm building so the next one to get written up. As said brought forward a bit in an aid to help those who may purchase a kit if they get the castings before I finish mine and want to get started.

Costings and details on how to order were posted last week on The Alyn Facebook page or you can make contact by the e-mail I provided. On the odd occasion that untouched casting sets have come up over the years they have fetched a premium price so the new kits should be a good buy for many who have been wanting one..

I did not pay for the kit in money, got it in return for helping out with pattern making etc, the Allman above I did pay for as I have done with others in their range. If I really costed out my CAD, CAM and CNC time I would say they got the better deal. Although I had mentioned to Graham several times that he should get the RLE available again even if just on the small one off basis he has been using I did not know they were going to release it until the FB post so was already well on my way with it and would have posted the build in due course.

There are members of this and other forums who have also done their part in getting the models available again, as the FB post mentions another member here has provided the transport to get the patterns to the foundry. I think I may also have posted here about a pattern I drew up for him. We are a like minded bunch who are happy to help each other out and have a liking for these models.

Edited By JasonB on 23/07/2023 16:32:21

Before machining the main crankcase casting of the RLE it is worth getting the bearing caps ready. These are supplied as one so after a skim cut to flatten the bottom and then the ends with the now flat bottom against the vice fixed jaw the casting can be cut in two. Well actually you can cut it into three as there is plenty of length and it's quicker to saw away a waste piece than turn it into chips.

I can see how Graham made the pattern many moons ago simply by gluing a piece of half round timber moulding onto a flat piece and adding a bit of draft around the edges. This gives the profile shown top right in the following photo and if we assume the radius of the "hump" is where the green sharpie mark is then most of the material needs to come off the bottom which combined with a bit of flattening of the hump results in the section shown top left. I went a bit further and used the excess height of the hump to provide enough material to form a boss that can later be drilled and tapped for an oil pot – middle bottom. Clearance hole scan be drilled and spot faced so the caps are ready for when they are needed.

The crankcase was shimmed up on the mill table to get it to sit nice and level and not be distorted by clamping pressure and the facemill used to flatten it's bottom. Now that I had a solid surface it could be set up on the table with some parallel packing below and set to get the best centre line of the casting in line with the mill's X-axis. I started out buy locating the four hold down bolt holes so they sat reasonably central to the cast bosses noting their positions on the DRO before spot facing to give the nuts a good surface to tighten down onto.

Next the vertical face that the cylinder flange mates to was squared up, just taking off the bare minimum at the top and down low enough that the flange clears the step left by machining away the draft angle. I later blended that small step in to leave a smooth fillet where the vertical meets the horizontal as I'm fussy like that..

Moving to the other end of the casting the bearing split line was milled down to the required 41mm above the bottom of the base and the stud holes drilled and tapped M4. You can see in the photo that I'm using a spiral flute tap, I've almost gone over to these exclusively as they cut well, clean out the swarf as they go and it means you only need to tap once not two or three times as you do with the usual set of three taps.

For the following operations I like to use a machining plate as it gives good flat surfaces that you can run a DTI against when setting up the irregular shaped casting and also gives a good surface to clamp down.

Here I have clocked the long edge of my well used machining plate true along the mill's X-axis, located that edge and established my ctr line a known distance from it (50mm in this case) and then using the previously noted DRO positions drilled and tapped so the casting can be screwed to the plate. The bearing caps were then screwed into place ready for boring.

Knowing the exact lathe ctr height above my cross slide and the thickness of the plate it was simple to work out how much packing was needed to bring the bearing split line upto ctr height, clock the edge of the plate true across the lathe and then start machining. First I used a 16mm 4-flute cutter to produce a flat edge by machining away the draft on the base and stopping just as the cutter touched the bearing cap. I followed up with a 6mm ctr cutting 3-flute cutter to remove the pip left by the conventional non ctr cutting endmill.

This flat surface could then be spot drilled followed by a 6mm stub drill and then the far end was done with long series ctr and 6mm drills. Following that a spot facer I had made for a previous engine was used to flatten the remaining three faces.

I could then drill out 10mm followed by reaming size for 12mm. If you want to take the option of having the crankshaft run in the cast iron then just drill to 9.7mm and then ream 10mm

A machine reamer was used to finish the holes to 12mm ready to accept the bearings.

That's enough for one night, next time the crankcase can be completed and these three main castings brought together. In the meantime a quick vid of the drilling and boring on the lathe and no the reamer is not going backwards!

While up at the head end of the engine I thought I would get the last couple of small castings out the way. Starting with the silencer (muffler) halves these were held in soft jaws to turn the overall diameter and the cast surface was cleaned up a bit at the same time.

The halves could now be held the other way around and the flange machined to thickness, a cavity turned with a boring bar and in the case of the half that screws to the exhaust pipe that was drilled and tapped 1/8" BSP.

Most builders will probably opt to turn three spacers to fit between the halves but I left the flange on one half thicker so I could mill most of the material away and just leave three integral spacers.

The other casting that can be dealt with now is the Mk2 carb. I started by holding it in the 4-jaw and got the needle boss to run as true as possible then faced the bottom and the stub that can be drilled part way and tapped M8 x 1 before continuing the hole right through and tapping M4 x 0.5 for the needle.

Holding by the spigot in a square collet block I could index the casting about to drill the long inlet hole and also drill and tap for the pipe that joins carb to head.

The last thing to do was spot face the four mounting holes with am 8mm milling cutter and then drill through 3mm for the screws that will hold the carb to the fuel tank top. Make a note of where the hole positions end up so they can be used when tapping the tank.

A quick group shot of the exhaust parts and carb.

It’s about time I wrote up a bit more of this engine build.

With a view to getting the gearing done I made the cam gear post first. Starting with some stock that wa slarge enough to get the rectangular head out of I turned two diameters, the larger for the gear to run on and the smaller to go into the hole in the engine frame.

Then into the spin indexer to shape the clevis.

After reaming the pivot pin hole and milling a flat on the spigot the clevis was slotted for the latch and then rounded over

I spent some time working out different combinations of metric gear size and numbers of teeth and in the end settled on a 50/25T combination using MOD0.7 which are available online for those that want to buy or cutters can be bought quite cheaply.

I started by roughing out a blank for the cam gear and then machined the cam profile which I made with a little less lift to suit the lever lengths of the newer head layout that has the exhaust valve further from the rocker arm pivot

Then with the gear blank mounted on an arbor set about cutting the teeth using the rotary table with dividing plates

The 25T crankshaft gear was cut in a similar way except I did it on the end of a bar before reaming and parting off once the teeth were done.

I like to set the gear positions using the actual gears so with a temporary crank shaft in place the small gear was slipped onto that and the larger gear on an arbor held in the mill’s collet chuck and the running fit and backlash adjusted by moving the engine’s frame in the X axis. Once happy the DRO was zeroed.

After which a flat was milled and a hole drilled and reamed

The MOD0.7 25/50 combination has a slightly larger PCD than the original design’s 1″ which put the hole a bit out of ctr to the cast lug.

A bit of milling and filing soon had that sorted out and a hole drilled and tapped for the screw that retains the cam gear post.