Another Engine Build

[Ron LadenParticipant @ronladen17547]

Thanks Jason, I am taking out of a piece of 1.75 inch square bar as I don't have any round large enough. Thought of putting a hole in for the boring head and centering it in the chuck on the RT. Then machining the outer rad and the flats then change over to clamping it on the flats and bore to the 20mm using the eccentric as a plug gauge. If I hold it via the flats I can probably stick with a 2.0 mm wall.

[Ron LadenParticipant @ronladen17547]

Finished the eccentric though I may make it again, its not quite to the drawing and to be honest I found it a bit tricky to make, probably my inexperience. The good thing is its spot on dimension wise and a nice finish on the running face it just looks a tad different.

[Ron LadenParticipant @ronladen17547]

Eccentric strap in cast iron it's the best I can do with it.

The wall thickness is tad heavier than the drawing and I have left all 3 lugs at 6mm, pleased with the fit to the eccentric, should run well.

[JasonBModerator @jasonb]

That should do the job.

Can't remember now but did you use a larger dia crankshaft as the boss for the eccentric looks thinner than mine?

[Ron LadenParticipant @ronladen17547]

Hi Jason, yes I had 10mm ground bar at the time and used that, probably a bad choice and should have turned it down to 8mm.

As for the thin walled boss, Shhh… your not supposed to notice things like that, all I can say is ​​​​​​. Anyway I have just sleeved it to 14mm which looks a bit better.

[Ron LadenParticipant @ronladen17547]

Bearing pedestals done just need a debur and a clean up.

[Ron LadenParticipant @ronladen17547]

Morning Jason, just checking but are the piston and valve rod glands fitted with full nuts and then a locknut?

Ron

[JasonBModerator @jasonb]

Yes

[Ron LadenParticipant @ronladen17547]

Jason, the valve rod is centered in the valve chest 5mm from the cylinder face. Half the width of the valve nut is 2.3mm plus the 1.0mm step in the valve slot plus the 2mm thick valve face which totals 5.3mm.? am I missing something..?

 

Edited By Ron Laden on 22/07/2020 08:41:06

[Ron LadenParticipant @ronladen17547]

Posted by Ron Laden on 22/07/2020 08:28:09:

Jason, the valve rod is centered in the valve chest 5mm from the cylinder face. Half the width of the valve nut is 2.3mm plus the 1.0mm step in the valve slot plus the 2mm thick valve face which totals 5.3mm.? am I missing something..?

Edited By Ron Laden on 22/07/2020 08:41:06

I am being dim this morning if I read the drawing correctly I would have seen the nut doesn't sit on the 1.0mm step but having said that I still can't see that the dims put the valve face to face with the cylinder..?

[JasonBModerator @jasonb]

Ron, sounds like you have got your nut the wrong way round and are putting it into the slot for the rod, if assembled correctly there is room for the valve to lift off the surface.

[Ron LadenParticipant @ronladen17547]

Hi Jason, I am in the process of finishing the valve parts and I am thinking of the parts fitting together as per your assy above so I think I have that correct. I was assuming that the valve would be a close face to face sliding fit with the cylinder with next to nothing in the way of any clearance, is that not the case..?

[JasonBModerator @jasonb]

Posted by Ron Laden on 22/07/2020 08:28:09:

Half the width of the valve nut is 2.3mm plus the 1.0mm step in the valve slot plus the 2mm thick valve face which totals 5.3mm.? am I missing something..?

Ron, this is where you are going wrong, if you look at that sectioned drawing I posted earlier you will see that the 1mm step is at the bottom of the rod slot not the nut slot.

This means that the nut is free to move off the face by 0.7mm ( 5 – [2 + 2.3]). This ability of the valve to lift off the surface is usual on slide valve engines as it allows any condensate that may gather in the end of the cylinder to be pushed out by the piston rather than being trapped and causing a hydraulic lock. As this engine has no drain cocks it becomes a more desirable feature.

In operation the steam or air entering the valve chest will push the face of the valve against the port face this is why it is important to ensure the valve moves freely on the nut/rod so that it can take up it's own position though not so free that there is slack at the end of it's stroke.

[Ron LadenParticipant @ronladen17547]

Thanks Jason, I did realise eventually that the 1mm step was at the bottom of the rod slot but I couldnt understand the 0.7mm movement but with your above explanation now I do, I had no idea it worked like that.

Ron

[Ron LadenParticipant @ronladen17547]

The Class 22 is awaiting a track test (next track day in two weeks) so thought I had better catch up and make the last few small parts for the Muncaster.

I made the valve this morning which seems to have turned out ok, Jasons drawing calls for bronze but not having any stock at the moment I went with free cutting brass in the hope it will be ok.

The rod slot is 2.6 mm wide x 4.0 mm deep and the nearest cutter I have is a 2.0 mm HSS 2 flute uncoated, the top end speed of the mill is 2500 rpm and I was a bit concerned how it would cope running at less than half speed. However it was fine and turned out ok, I started with a couple of 0.25mm cuts then increased to 0.5 mm and it cut just fine as did the two side cuts of 0.3 mm to achieve the 2.6 mm.

Valve and eccentric rods, the exhaust and a couple of oil cups will see the parts list complete.

[JasonBModerator @jasonb]

Not much to go now

[Ron LadenParticipant @ronladen17547]

No not much now Jason though I had forgotten the exhaust so I made that this morning. A bit of trial and error and a couple of failed attempts but got there in the end. I used some thick wall 1/4 o/d copper tube which I opened up to 4mm i/d. Clamped a 1/4 dowel to a block, heated the tube and formed it around the dowel. It did leave a slight flat on the outside of the bend but a smear of JB should cure that.

[Ron LadenParticipant @ronladen17547]

Oil cups made, they are a tad under size as I didn't have any 5mm hex brass only 3/16" hex so used that, should be ok.

Just waiting for a M2.5 die to arrive so I can make the eccentric and valve rods.

[Ron LadenParticipant @ronladen17547]

Hi Jason

I have a memory like a sieve can you please remind me of the UK supplier for the small head metric screws.

Thanks

Ron

[Ron LadenParticipant @ronladen17547]

Posted by Ron Laden on 06/05/2021 09:36:18:

Hi Jason

I have a memory like a sieve can you please remind me of the UK supplier for the small head metric screws.

Thanks

Ron

Found it Jason, Polly models, does the German supplier carry a larger range than Polly?

Ron

[JasonBModerator @jasonb]

Yes a much larger range. GHW

Edited By JasonB on 07/05/2021 07:31:46

[Ron LadenParticipant @ronladen17547]

Thanks Jason

Don't know if I am missing something but GHW only seem to list High Head Hex Steel M2.5 in one length 12mm, the ones I had from Polly were 15mm long.

[JasonBModerator @jasonb]

Don't tend to use the hex screws much preferring to use studs but thought Polly were the same, Knupher do other lengths but shorter. You are measuring thread length not O/A?

[Ron LadenParticipant @ronladen17547]

Thanks Jason,

I will go with studs also.

I need to make a new eccentric had a mishap with the original this morning, I was going through all the parts checking them against the drawings and for fit with mating parts. I found the groove in the eccentric measured 1.35 and not 1.5mm, dont quite understand that. It was some time back that I made the part but I was pretty sure I used a 1.5mm parting blade but it certainly is undersize.

I set it up in the 4 jaw to widen the slot and took it steady (probably too steady) and the tool grabbed making a mess of it. I could repair it but thought it better and probably quicker to produce a replacement.

These things are sent to try us.

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