Author Topic: The Alyn Foundry IF Allman engine.  (Read 4422 times)

Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #15 on: August 23, 2018, 07:05:14 PM »
Thank's Graham that will give me a height to add onto the top of this



I was aiming for 7 1/16" high but found that the Bangood cutter does not do a vertical edge so after this the A frame had a slight sideways lean >:(



I'll have a play around with the gear sizes as some of the smaller tooth counts are not so easy to cut as the ones from the likes of HPC have the right undercut as they are cut on a proper gear cutting machine.

Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #16 on: August 24, 2018, 07:12:00 AM »
I would have thought the original engine used whole unit imperial measurements JB  :noidea:

I have run the numbers on the original 24/12 tooth gears and the two options I have are: 20 DP which gives 34.3mm between centres or 24DP gives 28.56 between centres. I might try cutting them to see if they would run true  :thinking:

Jo
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Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #17 on: August 24, 2018, 07:34:02 AM »
I would have thought the original engine used whole unit imperial measurements JB  :noidea:

7.045 about as near as I could get to a WHOLE 179mm Jo  :LittleDevil: But if you want to do your own drawings then I'll just let Andy and Graham have copies of mine.

I wanted to keep as much metal on the casting as possible so that the pivot for the larger gear will be able to fit the top web of the A- Frame, as you can see there is not much to play with.  Attached is what there is to play with assuming I can get the bearing castings to finish up at 7/16", if I had come down to 7" that would leave me even less to play with.  Still need to decide whether to just tap and spot face the web or add a boss to give a more substantial fixing. This is why I am machining parts as I go along, not worth drawing something that can't be made from the castings we have.

I am also finding that the castings generally have about 1/32" machining allowance so again 1/32" off top and bottom would have given me 7 1/16" to get down to a nominal 7" would have been a lot more off the top so not consistant with the other castings and therefor probably not what Graham made it to. Any more off the bottom and the foot would have been too thin.

Graham. I've now got that "texture" on the castings so they do look more like the real thing :mischief:



J

« Last Edit: August 24, 2018, 07:43:27 AM by Jasonb »

Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #18 on: August 24, 2018, 07:51:24 AM »
So 24 DP Gears would be more appropriate then. I'll see if I can cut a pair today at work  :)

Jo

P.S. You have probably noticed the two Patent drawings are at slightly different scales
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Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #19 on: August 24, 2018, 07:59:03 AM »
Don't waste your time. You did not read what I said about the distance between the bore and the valley being too small.

12T 24DP gear is 0.580" OD Addendum 0.041, dedendum 0.052 so 0.186 off that mean the root to root distance across the gear is 0.394 so it's not going to fit a 1/2" crankshaft without all the teeth falling on the floor :insane:

Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #20 on: August 24, 2018, 08:22:59 AM »
So you said  ;)

I'll assume a 1/8" throw on the eccentric with 7/8" OD and leave a boss to suit cutting it afterwards I've just realised a slight change in design is needed to assist the timing because of the spacing of the gear teeth

Jo
« Last Edit: August 24, 2018, 09:16:44 AM by Jo »
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Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #21 on: August 24, 2018, 09:49:09 AM »
7/8" eccentric will leave you rather thin on the strap maybe 0.050" after it's been cleaned up ::)

Don't see why you would need the eccentric so large, the bigger timing gear could run on a 1/4 or 5/16" pivot so 5/8" OD would do.

Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #22 on: August 24, 2018, 10:55:14 AM »
I have decided the eccentric will be made when I am allowed the castings for this engine. In the meantime I will try machining the larger gear to see how they run together.

Jo
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Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #23 on: August 24, 2018, 11:25:29 AM »
I suppose we should also bear in mind that what is shown on a patent drawing does not actually reflect what would have been found on the engine if it had actually been made. Once they got round to some engravings of engines you can see they used more normal gears with a lot more teeth, just like this one I made earlier.






Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #24 on: August 24, 2018, 12:45:32 PM »
I didn't enjoy cutting the big gear having bits of teeth left all over the place  :paranoia: It looked better once I added an additional cut and fettled any strag ends.

They roll together ok wouldn't have any power but in this application they don't need to so I will let his lordship add those to his castings   :pinkelephant: and I will get on with what I should be doing while I wait for more castings from Graham  :-X

Jo
« Last Edit: August 24, 2018, 12:50:48 PM by Jo »
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Offline Alyn Foundry

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Re: The Alyn Foundry IF Allman engine.
« Reply #25 on: August 24, 2018, 03:30:26 PM »
Hi Jo.

Interesting looking gears, as you say they're not doing an awful lot.

I've just realised that Jason seems to have two inlet valve chests, is someone missing one?

I've just photographed my engine in the eccentric strap area. I too went as large as I could but with a 3/8" stroke overall.

Cheers Graham.

Offline Jo

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Re: The Alyn Foundry IF Allman engine.
« Reply #26 on: August 24, 2018, 03:35:39 PM »
I've just realised that Jason seems to have two inlet valve chests, is someone missing one?

Yes, that is Surus' one  :stickpoke:

Jo
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Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #27 on: August 25, 2018, 04:58:20 PM »
These Welsh MOTs seem to take a long time.

While waiting for the video I got a couple of bits joined together.



Those with a keen eye will see that I have started to effect the modifications from Grahams engine design  to one that more closely resembles the Patent.

Offline Alyn Foundry

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Re: The Alyn Foundry IF Allman engine.
« Reply #28 on: August 25, 2018, 05:45:23 PM »
Hi Jason.

Not so much the MOT but the weather and my son has to work really unsociable hours these days.

Perhaps you could show the readership how the inside of the cylinder outer looks like? I made the corebox with a series of concentric rings to get good contact to the liner. These contact points are where the various ports enter the cylinder proper.

As both you and Jo had pointed out I missed a few vital issues like the transfer through the piston and I totally missed the closed top to the water jacket. This hasn't really been a problem though, the engine runs quite happily and the 638 that holds things together has done nigh on 20 years now.

Nice progress.

Cheers Graham.

Offline Jasonb

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Re: The Alyn Foundry IF Allman engine.
« Reply #29 on: August 25, 2018, 08:23:54 PM »
As Graham says the cylinder casting has a number of annular recesses that when the liner is inserted become the water jacket. having them as complete rings makes for easy core making and also makes it more likely that you will get a true bore through them all rather than having an interrupted cut if they were just cast around the various through holes.

This shows the basic shape of the cored cavity after machining, There was another contact point about 1/2" down from the top but I have shown this removed and also a recess in the top edge to take a ring of CI bar that will close off the water space.



This shows a section through the cylinder casting, the liner will make contact at the areas where the diameter is smallest, I will have to cut away some of these parts so that the water can flow freely from top to bottom



This is a section with the liner and top ring in place



looking down into the cylinder you can see the areas that will contact the liner and the cavities which still have the cast texture, the blue pen mark is where I removed the upper cast in ring and the recess which my new top ring will sit in.



J