Author Topic: Sweet Pea build  (Read 8416 times)

Online Kim

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Re: Sweet Pea build
« Reply #150 on: April 15, 2021, 11:42:55 PM »
Steel rivets!  How are those to use? I've had a hard enough time with brass rivets. Seems like steel would be a challenge.

Kim

Offline Barneydog

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Re: Sweet Pea build
« Reply #151 on: April 16, 2021, 07:42:21 PM »
Thanks Don. Glad you are watching.

Kim,
They are iron not steel rivets. They are soft enough to rivet with a hammed and no heating. I used round headed rivets. I put a small countersink ready for the end to be riveted into. Sat on the anvil on my vice with the heads downwards. Couple of good whacks with a medium hammer and they are done. No need for a punch to round them off.

Todays job was to build up the cylinders and fit them. I cut some gaskets for the steam chest and its lid. The rear cover is refitted with a gasket there too. I have not fitted the front cover yet so I can see the movement of the piston.

The slide bar and crosshead are already on the left cylinder so that was the first. The holes for the fitting bolts on the frames had already been drilled by the previous builder. They should really have been left until the drilling jig can be used. This is the jig made earlier for the drilling of the cylinders. Here came todays issue. The holes are in the wrong place!! Measuring from the front of the frames to one of the holes they are at least 6mm out. I checked all other dimensions including wheel centres, axles to front of frame, con rods, coupling rods, piston rods etc. All are correct to the plans so what was wrong? No idea apart from the holes drilled wrongly. I sat the cylinder on the frame and positioned it so it sat correctly and marked the frame. I used the drilling jig clamped onto the frames to drill the holes correctly.

The smaller holes are the new holes. They are 5mm and match the M5 holes in the cylinder exactly so I fitted the cylinder.

The con rod is fitted to the wheel and the crosshead. The wheels turn well and the piston and crosshead move nicely. I had to cut a new slide bar as the original is too short. The motion bracket cannot be moved to fit as it would clash with the wheel.

The bracket needed a little metal removing from the bottom edge to clear the movement of the wheel and is bolted on at the same angle as the centre stretcher. I drilled the holes out and replaced the bolts with M3 stainless bolts.
The new slide bar was cut to size and had a small bracket bolted on the end. This was bolted to the motion bracket to hold it all solid.

The last part needed was the second part of the joint for the valve rod. This is 10mm square mild steel. It is drilled and tapped M5 near to one end. On the same end at ninety degrees a slot is milled to fit the end of its mate on the valve control rod. The rest is turned to round in the four jaw chuck and the end drilled and tapped M5. A lock nut is screwed onto the valve spindle and then this part followed it on. An M5 stainless bolt holds the two parts together. The pivot bolt is temporary and will be swapped for something better later.

The valve and its rods will need adjusting later but the left cylinder appears to be sitting and moving properly.


That's it for today. Tomorrow I hope to fit the other cylinder and then won't be back in the workshop until tuesday. I have missed my target of running on air by the weekend but hopefully it will not be far off.

Online Kim

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Re: Sweet Pea build
« Reply #152 on: April 16, 2021, 08:10:24 PM »
That is very cool!  You're getting so close!  Can't wait to see it all go around :)

 :popcorn:

Kim

Offline Barneydog

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Re: Sweet Pea build
« Reply #153 on: April 16, 2021, 08:13:44 PM »
Thanks Kim,

I am enticingly close. Be nice to see it doing what it's supposed to do......chuff chuff!!!!!!


Cheers

Julian

Offline Barneydog

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Re: Sweet Pea build
« Reply #154 on: April 16, 2021, 08:46:52 PM »
Hi Guys,

I have an issue.

The piston rings I have made are too strong and will not go onto the pistons. I have snapped two trying. They will not open enough to feed onto the pistons. Last night I reheated two to red and left them to cool naturally. Same problem this morning...they snapped!! They are 3mm wide and 3mm thick so perhaps too thick. Wondered if it is worth making them 1,2mm thick and putting two side by side in each slot.

Advice please.
What should I do to them to make them more "springy"?
Can I make new ones out of ptfe? 325 degree melting point.
Can I make then out of stainless? I have some stainless available but will it be "springy" enough?

Would it be easier to go to silicone O rings? Or graphite string? Or just buy some rings?


All sensible ideas gratefully accepted.

Cheers

Julian

Offline Barneydog

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Re: Sweet Pea build
« Reply #155 on: April 26, 2021, 06:10:17 PM »
Hi Guys,

I am afraid that there will be a slight lull in my activities on this loco. This is due to two reasons:-

One.   I have been to the hospital today as I have increasing arthritis in my thumb joins which is affecting my dexterity. The surgeon graciously inflicted a considerable amount of pain injecting steroid into the joint...not around it into it. Anyone who has had this will know what I mean. I am restricted to very light duties for a couple of weeks or so. I think a bottle of beer is probably the heaviest I am allowed but if this proves too onerous I will scale it down to drams of scotch. We will see!! I have three operations to look forward to in the coming year or so to continue to rectify these problems. Nothing progressed on Sweet Pea last week as I reacted to my second covid. Just one of those things when everything goes wrong at the same time!!

Two. Since I last posted I have mounted the cylinders and fitted the cross-heads with all the rods now complete. This has tightened everything up too much so I need to strip it all and check everything and fettle or realign whatever is needed. Hopefully this will be light work so may do a bit when I can. I will report back once it is completed.

Three. There was no way the rings were fitting so I have to alter them to reduce their size and thickness. I have some cast left over that was turned to size so I will at some point also make some spares. Also I have bought some high temp graphite loaded PTFE so I may attempt piston rings from that. Again as this progresses I will continue to take plenty pics and report back.

Cheers

Julian

Online crueby

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Re: Sweet Pea build
« Reply #156 on: April 26, 2021, 06:22:45 PM »
Best of luck with the recovery and take your time, we can wait!  Work your way up from a half glass of beer to the full bottle if needed!

 :cheers:

Offline RReid

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Re: Sweet Pea build
« Reply #157 on: April 26, 2021, 08:36:24 PM »
You could drink your beer through a straw, but only if no one is looking...
Ronald

Online Kim

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Re: Sweet Pea build
« Reply #158 on: April 26, 2021, 09:07:04 PM »
Hi Julian,
Sorry to hear about your trials... Hopefull, if you take the recovery slow and easy, all will get back to normal soon!

Kim

Offline Roger B

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Re: Sweet Pea build
« Reply #159 on: April 27, 2021, 11:48:18 AM »
Wishing you a quick recovery  :ThumbsUp:  :ThumbsUp:  :wine1:

Those piston rings look very thick to me to be fitted over the piston. Were cast iron rings in the original design or were the grooves designed for graphite string packing?
Best regards

Roger

Offline Stueng56

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Re: Sweet Pea build
« Reply #160 on: May 12, 2021, 10:51:18 PM »
Julian

I just found your build log a couple of days ago. Very impressive. I bought a part built Sweet Pea over a year ago but apart from gathering some more materials I havenít progressed at all yet.

I have been looking on you tube at a Sweet Pea build by Mr Factotum and it looks like he had a similar problem with the piston rings. He made them to the drawings 1/8 inch wide and 1/8 inch radial thickness but they kept breaking. He took advice and made new ones only 1/16 inch radial thickness and they worked OK. See link to his video :

Hope you find this useful

Stuart
 

Offline Barneydog

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Re: Sweet Pea build
« Reply #161 on: May 13, 2021, 11:26:54 AM »
Hi Guys,

Thanks for all your well wishes and comments.

I have now started to do some bits on the running gear built so far. Everything has been stripped off and will be refitted with a bit of fettling and adjustment. There are a couple of issues to be sorted before going further. The piston rings are an issue I will discuss with you later. My first problem that everything was getting tighter and tighter as more parts were added. While it is this tight there is no point in going further until the problem or problems are found and rectified.
Firstly the axles in the axle boxes were a little tight and needed easing. I also had very little clearance for sideways movement of the axles. They were pressing against the outer faces of the boxes. After investigation there was no option except to press the wheels off and reset them. I made two new axles a couple of millimetres longer. The shoulder the wheels sit against was exactly to the plans but made it tight so a millimetre each side allows the axle to float slightly. The axle boxes went in the four-jaw on the lathe for checking and facing squarely. Turns out they were not far out. I quartered the wheels again and fitted them back into the boxes and into the horns. They turned very easily but the axle boxes did not slide well in the horns. All four were attacked with a file to make them slide a nd twist better. This will allow for the axles to tilt slightly on uneven track. The springs were changed for some lighter ones as the ones I have that are meant for Sweet Pea are very strong and seem too inflexible. These will do for now and will be assessed when the loco is fully up to weight.
I had originally followed a plan to alter the mounting of the weighshaft to keep the valve timing more accurate. Refitting my bracket to the rear boxes the back wheels tightened up. I think the brackets put a slight twist on the boxes so no good. My other plan if this mod failed was to convert to walchaerts which is the path I am now taking. I will detail the parts another time when they are made.

Cheers

Julian.