Author Topic: Rays Latest Engine - AKA Alyn Foundry RLE  (Read 13853 times)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9463
  • Surrey, UK
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #15 on: August 01, 2020, 10:25:02 AM »
I wonder if you would have had more luck using a bit of CI bar, with that many failing it may have been the iron or a slight flaw in it. Viton should work well and you could probably get away with one which should allow for longer coasting between hits.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #16 on: August 01, 2020, 04:48:55 PM »
Hi Jason,
The material was fine and machined nicely..
I think it was the width of the rings ( 1/8" as per plan)  that made them too inflexible. There was no groove depth shown on the plan and I scaled it at 3/32", resulting in quite chunky rings.
I did manage to get one into the first ring groove by feeding it in spirally, but there was no way a second ring would have gone past that into the second groove. Even though the rings all fitted in to the cylinder with a couple of thou gap, and the internal diameter was slightly larger than the diameter of the ring groove, I simply could not get the piston into the cylinder even with just the one ring fitted. I can only assume that the ring was not sitting right down in the groove for some reason.
As a point of interest, the ring grooves on the Robinson were only half the width, at 1/16"
After several attempts at fitting/removing rings, as I said in my previous post, I decided to go for Viton rings, which I have now fitted, and which already appear to be giving good compression.
Ray

Online Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #17 on: August 01, 2020, 07:05:31 PM »
Hi Ray.

The piston casting was a " Buckley " grade M, quite soft so I'm not surprised they broke. Sadly I never got round to amending the notes on construction.

For all my piston rings made these days I use a simple 90/1000" square form with a 95/1000" deep groove.

However....

Viton is now the material of choice for us.

Cheers Graham.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #18 on: August 15, 2020, 04:30:56 PM »
I have just spent a couple of very frustrating days machining the cylinder head.
I started by facing the flat side of the casting and as there was no dimension on the cylinder head drawing for the thickness, I just took enough off to get a perfectly level surface, this becoming the datum from which the depth of valve pockets was measured. All went OK and the valve guides, valve pockets and valve seats were all completed, before turning my attention to the two 1/8BSP threaded ports.

The exhaust port, which is in the side of the T of the casting, should be directly in line with the valve pocket, but when I drilled it, it fell partly into the pocket and partly into the valve guide. By measuring the depth of the valve pocket and transferring the measurement to the face of the T, it was clear that this would be the case so to overcome the problem as far as possible, I had already moved the port as far to one side as possible but this still did not rectify the problem.

The diagonal hole connecting the inlet port to the inlet valve pocket also cut slightly into the valve guide.

I was completely puzzled how this had happened and all became clear this morning when I happened to look at the General Arrangement drawing and discovered the the missing dimension (5/16") was on that, rather than on the Cylinder Head drawing where you would expect to find it.
I now had a dilemma -  do I reduce the head thickness from its present 1/2" or do I leave it as it is and compensate with longer valves, pushrod and whatever else would be affected?
In the end I decided to re-machine the head, which also involved cutting new valve pockets and seats. Although I set the head casting up on the milling machine so that a 3/16" drill moved smoothly up and down through the valve guide, when I cut the new pockets, they were not completely concentric with the old ones, so I don't know now which ones are square with the valve guides. I will only know once I make and fit the valves. If the valves do not seal on the new seats, I may have no alternative but to drill the pockets out, plug with cast iron plugs and re drill.

Ray

Online Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #19 on: August 17, 2020, 11:22:26 AM »
Good morning Ray.

If I've read your last paragraph correctly then no, you shouldn't have any problems getting a seat for the valves as you cut them from the original setting. The pockets might not be concentric but that doesn't really matter.

If you've left a little extra on the depth of the cylinder head casting then you will need to extend the valve stems accordingly. Once the assembly of head, cylinder and hopper are bolted to the mainframe and your timing gears placed you can then find the " true " length of the pushrod.

Cheers Graham.

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #20 on: August 17, 2020, 11:37:29 AM »
Hi Graham,

I have made the valves and they seem to seal OK on their seats when I blow into the threaded ports.
As I am reversing the inlet and exhaust valves, does that mean that the exhaust valve should now be the longer of the two? Was there any reason for the two being of different lengths?

I have made the valves to the lengths as per drawing, but on the shorter one, when the collet is fitted, it almost touches the top of the nipple, giving zero room for a spring so it looks as if I may have to make that one longer anyway.
Ray

Online Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #21 on: August 17, 2020, 12:23:20 PM »
Hi Ray.

I've just been for a refresh on the drawings.

The inlet, being atmospherically operated needs a light spring so a little extra was added to help with this issue. Although the drawing shows the springs sitting on top of the nipples you can always allow them to slide over them to sit at the base. I made " piloted " tube cutters from Silver Steel that accurately cut the OD of the nipples down in diameter to fit parallel springs, you could, however make some conical ones.   ;)

Because you're reversing the arrangement you will need to make the rocker arm longer with an outward curve to " pass over " the inlet valve stem. I'm sure I posted a picture of mine on Jo's Roy's little engine thread? Let me know, I can always take another for you?

Cheers Graham.

Addendum.

Here's the link Ray.

http://www.modelenginemaker.com/index.php/topic,7664.msg163289.html#msg163289
« Last Edit: August 17, 2020, 01:05:38 PM by Alyn Foundry »

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #22 on: August 17, 2020, 01:11:47 PM »
Thanks Graham,
I think I will make another exhaust valve the same length as the inlet as that one seems plenty long enough
.
I am not very happy anyway with the fit of the valve stems in the guides. The reamer I used seems to have cut slightly oversize as a result of which there is quite a bit of sideways movement on the valves.

I am debating whether to remake the valves with slightly larger stems to fit the guides, or alternatively, I could bore out and sleeve the guides, but I would still have the problem of ensuring squareness and concentricity with the valve seats. The other option is to leave as is and see if the loose fit causes any problems when I try to run the engine, then make any modifications required at that stage.
Just very annoyed with myself for not spotting the thickness dimension which has led to all these problems.
Ray

Online Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #23 on: August 17, 2020, 01:21:50 PM »
Hi Ray.

Typical Welsh summer, it's raining again lol.

My workshop is flooded again so it's back to armchair engineering.

Please don't try to fit guides, just make a couple of new valves with the oversized stems. I've got over 50 reamers, all seem to cut a little differently to each other. Over the years I've learned to use the ones best suited to a particular job.

Cheers Graham.

Offline michaelr

  • Full Member
  • ****
  • Posts: 163
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #24 on: August 17, 2020, 03:31:45 PM »
 Ray, Having built the RLE engine (Two in fact) I'm watching your build with interest, I did the reversed Inlet/Exhaust fitted a curved over rocker arm, both valves same length.

MichaelR

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #25 on: August 17, 2020, 07:24:30 PM »
Hi Michael,
Thanks for your interest. I like your rocker and was planning something similar. For some reason I seem to be making hard work of the cylinder head. I did try larger valve stems as suggested by Graham, but it looks like the valve guide holes are slightly oval so I have no option but to open them out to 5mm so that I can use 5mm silver steel for the valve stems.


Ray

Offline michaelr

  • Full Member
  • ****
  • Posts: 163
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #26 on: August 17, 2020, 08:03:14 PM »
Hi Ray.
I'm sure you will overcome the valve guide problem, I turned the valves for my engine from stainless steel.

MichaelR

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #27 on: August 17, 2020, 08:38:04 PM »
Thanks Michael. I made a drilling jig that fitted tightly in the valve pocket and against the face of the cylinder head and opened up the guides by running a 5mm drill through them. Have to order some 5mm drill rod, then I will make the valves by silver soldering a stainless disc to one end, then machining to size with the stem held in a collet.
Ray

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9463
  • Surrey, UK
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #28 on: August 18, 2020, 07:04:10 AM »
Ray did you also drill the previous hole? I prefer to ream my guides as it gives a rounder hole and closer to size which may be where your problem came from or could be that SS can be tri-lobed due to the grinding process. I then turn my valves to fit the reamed hole from solid

Offline RayW

  • Full Member
  • ****
  • Posts: 735
Re: Rays Latest Engine - AKA Alyn Foundry RLE
« Reply #29 on: August 18, 2020, 09:37:27 AM »
Hi Jason,
The original holes were drilled undersized then reamed. I think the problem was caused when I realised that the thickness of the head was wrong and I had to turn it down which meant machining away the valve seats and quite a bit of the valve pockets.
In order to set the thinner head up for reboring the pockets and recutting the valve seats I used a 3/16" drill bit in the mill and adjusted the position of the head casting until the drill bit appeared to slide smoothly up and down through the valve guide. I suspect now that things may not have been perfectly vertical as I thought, resulting in the guides being damaged.
I do not have a 5mm reamer so keeping fingers crossed that the 5mm drill bit I used will have given a sufficiently good finish.
Ray

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal