The Alyn Foundry IF Allman engine.

[Jasonb]

Here for the benefit of Jo is a good example of the way I have had to deviate form the Patent drawings to make best use of the castings that I have to work with, had I just been making one for myself I may well have ditched some of the castings and substituted scratch built parts but as she and Andy are hoping to use the castings I have done what I can with them.

The extract below taken from the patent drawings shows the flywheel hub protruding about 5/32" either side of the rim's width, there are substantial overhangs of the bearing blocks beyond the width of the A frames legs either side and when in its highest position the eccentric is below the underside of the A frames top.



The reality is that I have had to machine the hub flush on one side of the flywheel and can only have 1/32" proud the other. The tops of the A frames have had to be trimmed almost flush with the legs so the bearing blocks hardly have any overhang. The eccentric has had to be placed part way within the width of the a frames legs & butt it up against the gear and a large clearance cut away on the underside of the A frame to stop it hitting the same. i would have liked to have got the eccentric even further from the A frame as it puts the linkage in the wrong place but will have to get around that. I have yet to decide if the pully will have to move out further to allow the follower roller to fit or if I follow the patent and have it up against the bearing in which case a large chunk will need milling away for clearance



Jo, If you can come up with better then good luck with that.

[Jasonb]

Just to keep Jo  in the loop, with the eccentric now in position thought can be given to the exhaust rocker. Once a gain the Patent drawing is more artistic than technical, the two drawings have the cross shaft at different heights to start with and both have the shaft passing partly  through the base and leg of the A frame as shown on the attached image which does not show the studs and nuts which would also clash.

This seems to be the best work around with the shaft just clear of the A frame and a very close fit to the nut, I have already had to drop down to 5BA fixings due to lack of room but would have liked to use 4BA. It would be better if the pivot could be moved towards the cylinder more but that mucks up the geometry of the exhaust rocker which even as I have shown it has a lot of upward movement when you really want in inwards only. This may be why the early production engines show the large horizontal rocker arm as they too found there patent did not work in the real world.

<a href="https://www.youtube.com/watch?v=4xsx3fDFhtk" target="_blank">http://www.youtube.com/watch?v=4xsx3fDFhtk</a>

[Alyn Foundry]

Hi Jason.

Yes the whole thing is a little tight! I'm uncertain whether I had to slightly relieve the " A " frame to allow for the rocker shaft.

However, if I may take you back to here?

http://www.modelenginemaker.com/index.php/topic,8381.msg183689.html#msg183689

At 1:56 on you can clearly see the " elliptical " nature of the exhaust valve action. A little " peck " is all that's required.

Cheers Graham.

[Jasonb]

Yes it does not need to open much and probably even less so with the upper exhaust working as that will let any expanding gas out. Infact it looks to let out more gas than would be idea as it does shorten the power stroke which can be seen as your engine increased speed as the plug was put back in.

The other thing on the patent drawing is that the top view seems to show the exhaust block fitting directly to or part of the cylinder jacket which would move everything closer to the cylinder for better geometry. The other Allman that I made was all cast as one and it was a right pig to machine the exhaust valve seat as you have ti come in from the far side via the inlet.



For anyone following along this shows the large horizontal rocker used on the early production engines.

[Jasonb]

One down, one to go. The perspective of the photo ,makes the are look the same width but it does taper from 1/4" at the boss to 5/32" before going back to 1/4" around the slot. I will probably draw the slot a lot shorter as it does not really need to be that long. All from one bit not soldered up which will please Jo.

[Chipmaster]

That looks good Jason.

Andy

[Alyn Foundry]

Hi Jason.

It's difficult to tell, is that made from Steel or Brass?

I used taper pins for fixing the levers once the correct positions had been ascertained.

Cheers Graham.

[Jasonb]

Steel, since I changed to LED strip lights the photos on my camera are coming out a bit orange which is odd as they give off a slightly whiter light

Yes that one is already pinned with a 1/16" taper pin, other is finished and just needs to be pinned.

[Jasonb]

All done and working and a better colour from the Phone.

[Jasonb]

Although the bailing wire to hold the chimney had some appeal I decided on a rigid bracket much like the one that is cast into the chimney. But unlike the casting I did not include a boss for a burner as, like Graham I will make a burner ring and besides the burner is shown at the front on the patent not the rear. A bit of stainless steel swarf later and I have this, actually slightly smaller diameter over the bead and a 1/16" shorter than the cast item.





Also bent up a bit of 1/8" rod fpr the governor linkage remembering to slip teh pivot on before the second bend

[Dave Otto]

Everything is looking very nice Jason, the exhaust linkage turned out beautiful.

Dave

[Jasonb]

Question for Graham

I'm now looking at the gas valve, did you fit an internal spring to keep the plunger pressed against the valve seat as there is no room below for a spring and without one the gas would want to lift the valve off of it's seat.

I have managed to put the valve casting on a bit of a diet but still quite a bit larger than on the patent but may still be able to loose a bit more once I know what has to go inside.

BTW it seems a good casting so far.

J

PS Jo are you out there or have the Moles got you?

[Alyn Foundry]

Hi Jason.

I've been unable to see properly for a few days, conjunctivitis, like trying to see the road through a broken toughened glass windscreen.

The progress looks good.

Yes, I used an off the shelf Brass 1/8" BSP flange plug to seal the top of the valve. I counter bored it for a spring that pressed against the top of the valve. The valve head also had a " nipple " that stopped the spring from moving sideways.

I opted for the gas supply to be on the top of the valve so that any leakage down the stem would be minimal and only occur when it opens. The Gardner uses the same method.

Cheers Graham.

[Alyn Foundry]

Jason.

Upon closer inspection I notice you have used a different approach to me for the governor arm.

How do you intend to stop the horizontal section from moving sideways. I securely fixed the vertical portion to a pivot that was fixed to the " A " frame leg.

[Jasonb]

Yes I found it wants to move about, think I will change to a boss that fits to the side of that pivot with a rod top and bottom of the boss which actually looks a bit more like the Patent, which also shows an additional guide lower down.

Thanks for confirming my thoughts on the valve.