Reboring Cylinders

[doubletop]

You may see in some of my posts reference to a Simplex I've purchased to refurbish. From what I can tell it hasn't been run for 10 years and I bought it knowing it needed some work doing. That said the boiler has been both hydraulic and steam tested and given the OK by club boiler inspectors. I'll get it formally certified once I've re-built it.

My question

The cylinders are cast iron with cast iron pistons and graphited packing. The bores are in sorry state with a bit of rust and old steam oil. As it is a Simplex with 1.5" bores I am thinking of boring it out the extra 1/16" to Super Simplex dimensions of 1-9/16" remaking the pistons and rods and fitting proper rings. I need to remake the pistons and rods as the cross heads are shot as well and the hole for pin through the rod is oversize.

So should I do what I'm planning or just try and hone out the bores and make gunmetal pistons and use viton rings. Or do something else?

Pete

 

[Tin Falcon]

Not an expert on restorations by any means so take my free advice for what it is worth but IMHO go for the easiest least invasive procedure. i would hone the cylinders and polish the piston and repack the rings.
if I am reading this correctly you have a 1 1/2 inch bore so no problem using a hone from the auto parts store for reconditioning brake parts.
as far as the pistons you should be able to spin those up in the lathe and polish them as well

Tin

 

[Blogwitch]

Pete,

As you know, I am not into locos, but have done a fair amount of old model steam engine refurbs.

The way I always look at it is to bring it back to standard as much as possible, but in your case, unless you re-sleeve the bores, you can't.

If I was to do it, I would go for your option of making the cylinders the same as the Super Simplex, then at least there will be a set of plans and information that can be passed on to future owners so they would not be scrabbling around in the dark trying to see what had been done to it.

Plus, if the boiler can generate enough steam, a bit more pulling power to the wheels.


John

 

[doc1955]

I think I have to agree with John I would take it to the super plans but I have not done much in the way of steam engine refurbs.

 

[MachineTom]

The case that I am working on is similar to yours. An unfinished project started decades ago by persons unknown. I'd bore it next size, make new piston and rings and complete everything the way you want it.

 

[doubletop]

Thanks guys, I’m now happy that I should do it

I did have one comment that the existing cylinders were too large a diameter for the boiler, but I don't think that is a commonly held view. The increase of 1/16" on the diameter is an increase in area of about 8% and I believe that Martin Evans increased the grate size on the Super to compensate, however there is another view that the quoted increase in grate size wasn't real so is it really going to make a difference? There was also an opinion just to make new pistons and rings to the original size and let them scrape it clean……..

Those aside; can we look at the options for re-boring the cylinders? As I see it the primary objective is to ensure the new bore is concentric with the original and the rear (gland) face remains square to the bore. The options I see available are

Faceplate and right angle plate
4-jaw chuck
Faceplate and Keats plate
Boring bar and job on the cross slide
Boring head on the mill

I sort of have these in my order of preference

The first one is there because of John Slater's recent article in the MEW (190) "locating work accurately on the faceplate" by using buttons to accurately offset the angle plate from the center and then mounting the cylinder by the mounting face on the angle plate. It looks appealing in the ease it allows the setup to be achieved.

I’m not keen on the boring bar, I’ve never used one before. That may be fine if I was starting from scratch as I’d have plenty of meat to work with to get it right, but I’ve only got to remove 1/32” before I’m done.

I don't have a Keats Plate and the boring head in the mill is last because my lathe has a self act that's really slow and my mill doesn't.

Is there any value in doing something like using a 1.5" mandrel turned between centers to line things up and then removing it before boring?

Any views on how I should go about this please?

Pete

 

[kvom]

If the faces of the cylinder are square to the bore then faceplate and right angle plate look to be a good choice. My lathe boring bars are a lot more rigid than for the mill since I can adjust the length in the holder to the minimum needed. And the feed/rev on the lathe can be a lot smaller as well.

 

[doubletop]

Thanks Kvom

I'm coming to the same conclusion. The mounting face should be parallel to the bore and if it isn't this is an opportunity to correct it. I'm still considering trying the mandrel between centers for lining things up. I'll be able to get it out and remove the morse taper centre through the bore prior to machining.

Pete

 

[MachineTom]

The statement about the mill and boring head is too vague for me. But, I'd use the mill and be done before you have the cylinders centered in the lathe with a face plathe and hold downs.

Chck the bore to face with a square, and the faces to each other, then mount with the face that is closest to 90°, on the table, bore away, skim the topside face to get it parallel to the table face, now move to the next task.

Witout knowing what machinery you have it is a guess that you have a mill, in tram, and clamps blocks etc.

 

[doubletop]

Tom

I can see how easy the setup would be but I'm not confident in achieving the result

A lot of the stuff I do I'm doing for the first time. I haven't used a boring head in my mill so I don't really want to try for the first time on this job. My boring head is not too flash either. That's really the reason this option ended up on the end of my list.

Pete

 

[SBWHART]

Hi Pete

Bought myself an 90% complete supper simplex about a month ago, only thing I can add is that the builder fitted it with a belpher boiler, don't know if that was done to compensate for lack of steam, ?.

I'll be watching you're referb with interest.

Stew

 

[doubletop]

Stew

I was thinking the same about you completing yours. Are you going to strip it an check it before you do the final 10% just to ensure its to your standards?

I'm also not convinced about this lack of steam issue though. Before I stripped it down I steamed mine up at the club the other month under the supervision of the club boiler inspector. It was the first time I'd coal fired a boiler from the start. After a while of frankly messing about he came over and showed me what I should have been doing. Before long we had a roaring fire over the entire grate and more steam than we could use. His comment "you'll have no trouble making enough steam with that"

We could start a debate on Simplex steaming but I'd guess there are so many variables, not least of which is the operator, that any conclusion would probably be subjective.

Pete

 

[SBWHART]

Hi Pete

My plan is to complete the plumbing etc to get it to a state when it can be steamed the boiler has been pressure tested, but not steamed, it turns over Nice and free, but the finish of the motion works has a lot to be desired, the experts on this things at the club gave it the once over and poited out one or two things that could be corrected ie:- blast pipe not central with the chimney, so once its been steam tested, I'm planning to tidy things up and give it a new paint job.

Before i get started though I have an article to write for ME ;D

My first job will be making the boiler feed pump, I've got the drawing for the supper simplex pump that's suposed to be a great improvement on the origonal.

At our club we have a fair few simplexes that are regularly run, one guy did a production run of 4 engines sold, them all to club member at £3000 each, so we have plenty of people to pester with ?.

Stew