Author Topic: Building a Muncaster entablature engine  (Read 23037 times)

Offline Gas_mantle

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Building a Muncaster entablature engine
« on: September 16, 2017, 07:31:48 PM »
Hi all,

Having just completed a fairly simple barstock engine I've been on the look out for something else build that may be of interest to other members with limited tooling and experience. I like the look of Muncasters entablature engine so Jason kindly emailed me a set of plans along with a photo guide on how to go about making the engine and I've decided to give it a go and show the progress here.

For those unfamiliar with the design here is what I'm hoping to achieve  :)



I'll show most stages of the build including any mistakes and would appreciate if other members can point out better ways of doing things or generally offer advice, comments etc.

Anyway lets get started an see if I can turn this pile of metal into an engine.



First job is to square off a piece of 50mm square cast iron 38mm long that will form the cylinder and mark a centre to locate the bore. The cylinder bore at this stage isn't central as a lot of material will later be machined away leaving a flat face for the slide valve. The lowest face is to be the valve face and is 23mm from the cylinder bore centre line..



Next step is to turn and face a 38mm end flange and bore out the 24 mm bore.  I'm not sure this crude method with a wiggler and a dial indicator is the best way to centre the part but it does work.





This will be the flange to accept the cylinder cover.



With the flange done it's on to cutting the main bore at 24 mm



It was my intention to complete this part before starting this build log but I've decided to stop work for today as the finish I'm getting in the bore is poor  :(   I have about another 2mm to open out the bore so it isn't a problem yet but I need to figure out why the finish is gritty.

I'm using new brazed carbide tipped tools, they are on centre but even after trying different speeds, feed rates etc it makes little difference  :(



Anyway, I'll have a think and try to complete the part tomorrow  :)

Peter.




Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #1 on: September 16, 2017, 08:02:06 PM »
Off to a good start Peter, how do you find working with cast iron?

I prefer to do the finishing cuts for cylinders with a reasonably solid boring bar that takes HSS toolbits. You may also want to check that the bottom edge of your boring bar is not rubbing on the bore.



J

PS as you are making it to the drawing sizes the "O" ring size is 19.6mm ID x 2.4mm Cross Section, I got mine from Sealforce.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #2 on: September 16, 2017, 08:12:48 PM »
Thanks,

I find the cast iron is fine for milling and turning, having never used it before I expected it to be tough as old boots but it cuts easily.

The boring bar isn't rubbing and it's a brand new tool, I'll have a play around with the angle its set at tomorrow. I also have a bar with an indexable tip I can try, failing that I'll make a more solid bar like you suggest.

In the past I've used graphite string as piston rings but think I'll try O rings this time, do I need to order a particular type to withstand steam ?

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #3 on: September 16, 2017, 08:22:59 PM »
I used a vitron one.

Offline Chipswitheverything

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Re: Building a Muncaster entablature engine
« Reply #4 on: September 16, 2017, 08:32:13 PM »
Hi Peter, nice start to your project.  I'd go with Jason on the suggestion of using a HSS insert bit in a boring bar, which you have ground up yourself to suit the job.  Hone a nice, polished and very sharp small radius on the extreme business end of the insert bit.   A tip that Geo. H Thomas had about boring was to set the tool just a little above centre height, say ten or fifteen thou, then if the bar bends a little under the cut it doesn't dig the tool tip down into the finished surface of the bore as can happen when it is on dead ctr. height.  Gives it that whisker of relief into free space as the bar bends...    Dave

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #5 on: September 16, 2017, 08:41:27 PM »
Thanks, it looks like a more substantial bar with HSS is the way forward.

It seems like the brazed carbide one creates swarf like grains of sand on fine cuts, I get the impression the swarf isn't clearing properly and scraping the bore. Is it worth buying a honing kit to finish the job after I've bored it out as I want it to run on steam ?  I've ordered some Viton rings.


Offline Jim Nic

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Re: Building a Muncaster entablature engine
« Reply #6 on: September 16, 2017, 09:42:36 PM »
Hi Peter
A good start and good to know when to stop before you get to the point where it's too late (a lesson I wish I had heeded before I messed up a brass part today  :Doh: )
As to honing the bore, I obtained a car brake cylinder hone from e-bay for about £7 which worked a treat on the last cast iron cylinder I did.  I fixed the cylinder in the vice and used the hone in a hand held drill with some oil to help things along.  It didn't take off much metal but left a superb finish.  I then made the piston a slack fit and sealed it with an O ring.
Jim
The person who never made a mistake never made anything.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #7 on: September 16, 2017, 09:54:03 PM »
Thanks Jim,

This is the kind of thing I was considering, it's able to cope with any size of cylinder I'm likely to make.

https://www.amazon.co.uk/KS-Tools-150-1185-Cylinder-%C3%9819-69mm/dp/B007XUKD2K/ref=sr_1_18?ie=UTF8&qid=1505594900&sr=8-18&keywords=hone

I've had another look at the part and once all the grit has been cleaned out with an oily rag, it's better than I thought but does still need improving a bit.

Offline b.lindsey

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Re: Building a Muncaster entablature engine
« Reply #8 on: September 16, 2017, 09:57:02 PM »
Great start Peter and thanks for posting a picture of where you are headed too, that helps a lot. I think you will find the CI a joy to work with, just clean up well at the end of each session.

Bill

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #9 on: September 16, 2017, 10:00:21 PM »
Cheers Bill, if I can figure out how to upload a PDF file here I show a plan of the part I'm working on to help others understand what I'm trying to achieve.

Offline b.lindsey

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Re: Building a Muncaster entablature engine
« Reply #10 on: September 16, 2017, 10:03:41 PM »
You should be able to attach it just as you would a picture at the end of your post.

Bill

Offline Brian Rupnow

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Re: Building a Muncaster entablature engine
« Reply #11 on: September 16, 2017, 10:04:51 PM »
That hone which is in your link will work fine. I've built about a dozen steam engines with cast iron cylinders, and I drill the cylinder bore until it is about 0.025" from full size, then finish with a straight flute reamer. I've never been a fan of boring to final size, because I never could get the finish I wanted with a boring tool.--Of course, you have to spend the money for a reamer, but then you have it forever. I wouldn't get too excited about a "glass smooth surface" on the bore. You might wear the first Viton ring out quickly, but the ring will quickly smooth the bore  to an almost glass like finish anyways. The Viton rings are cheap.---One word of warning---Make sure before you spend the money on a hone that it will collapse to a small enough diameter to fit in the bore.

Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #12 on: September 16, 2017, 10:39:41 PM »
I bought one brazed carbide boring bar, used it once, and never again.

Offline Florian Eberhard

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Re: Building a Muncaster entablature engine
« Reply #13 on: September 16, 2017, 11:08:06 PM »
Hi Peter

Well the thing with the carbide bars is the following:
<a href="https://www.youtube.com/watch?v=7ngNtK9tKME" target="_blank">http://www.youtube.com/watch?v=7ngNtK9tKME</a> (jump to 10:45) - at least if yours is like those standard chinese boring bars.

Florian

Offline steam guy willy

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Re: Building a Muncaster entablature engine
« Reply #14 on: September 16, 2017, 11:24:35 PM »
just an idea when using a boring bar........could you make it extra long so it fits inside the bore of the headstock mandrel. it could have an oilite  bush on the end and this would stop any deflection ?? !!! I have not done this myself ...just a bit of inspiration...thinking inside the box/mandrel !!!

 

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