Author Topic: Building a Muncaster entablature engine  (Read 23042 times)

Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #45 on: September 22, 2017, 09:20:24 PM »
Motion study from Solidworks

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #46 on: September 23, 2017, 07:35:29 PM »
With the cylinder largely complete it's on to the valve chest and cover next  (I have ordered a cylinder hone as suggested  :)  )

The chest assembly is made from the now diminishing piece of 50mm square cast iron the first job being to mill the chest and cover square and to the required 27mm wide to match the port face



A 2.5mm hole is drilled in the top of the chest to take the valve rod



The valve hole is then opened out to 5mm a short way to accept gland packing later and the parts are now machined to length leaving a 3mm high protrusion which will later be profiled to an elliptical boss.



The valve chamber is an 11mm wide rectangular slot, I had thought of chain drilling the centre but a 10mm slot drill got me near to size in seconds



The smallest mill I have with enough reach is 5mm so I am left with radiused corners but I don't think they will affect valve travel and I can always file them square later if need be.



With 8 holes to drill and tap to attach 3 parts together I wanted to drill them all together but found the whole assembly too tall for the mill vice but a bit of double sided sticky tape should do the job.



I guess it looks a bit amateurish but I've used this technique before to keep parts aligned and it works well



With a set square to check the alignment we are ready to go



I intend using 7Ba studs so i drill a pair of 2mm holes (it may look to be leaning but it is actually vertical)



Will 2 tapped holes I can now bolt the parts together to drill the remainder



So now it's on to milling the cover down to 2.5 thick and cutting a decorative recess where most modellers like to add a red letter 'S' even if they aren't called Stephen, Shaun, Simon etc  :pinkelephant:



A bit of a clean up and this is the result so far.







Peter.

















Offline b.lindsey

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Re: Building a Muncaster entablature engine
« Reply #47 on: September 23, 2017, 07:43:49 PM »
Wonderful progress Peter, and a nice looking cylinder assembly!!

Bill

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #48 on: September 30, 2017, 03:58:16 PM »
Thanks Bill  :)

With the cylinder and valve chest largely done I've decided to move to the top of the engine and do the bearing blocks next, I'd like to have done the base plate or the columns but think I may need a few extra tools to tackle them.

The engine has 2 split bearing blocks made from 8mm thick steel with bronze (or in my case brass) bearings.

With the halves milled square it's onto marking and drilling for the securing bolts and to house the oil cups.





I wanted to secure the 2 halves together before drilling the crank holes so with 1 done it's onto the next



A wiggler set to centre the assembly then through with a 10mm slot drill.





Part of the material around the bolt holes needs removing with a 6mm slot drill



Using a similar technique to rounding the cylinder profile I nibble away with a mill and then file to start forming the rounded tops - here it isn't complete but starting to take shape.





A pair of bobbin shaped brass bearings and threaded supports for the oil cups turned in the lathe and here's where I'm at.





A little bit more profiling to do on the tops but they pretty much finished  :)

Peter






« Last Edit: September 30, 2017, 04:42:33 PM by Gas_mantle »

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #49 on: September 30, 2017, 04:12:53 PM »
Peter, what height is your pedestal split at? It looks a bit low although that may just be the thicker feet throwing my eye.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #50 on: September 30, 2017, 04:31:56 PM »
Hi Jason, I've just measured and it's 13.5 mm, your plans called for 14mm but to be honest I started getting in a mess with them and had to trim a bit to true them up. The centre line of the bearing is true though, and a silver steel rod is only a few thou difference in height end to end.

I think I'll make the feet thinner and see what they are like once fully done but if need be I'll make 2 new ones  :(

By the way I bought a cheap hone and did the cylinder, the result looks fine.

I had a few beers with the guy making my boiler last week, I should have it in 4 - 5 weeks so with a bit of luck I should have it ready to try with this engine :-)

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #51 on: September 30, 2017, 06:38:46 PM »
0.5mm should not be a problem, you can loose that where the piston rod screws into the cross head.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #52 on: October 13, 2017, 07:14:59 PM »
Having had to wait for a few more materials things stalled for a while but I've now managed to make significant progress  :)

First to tackle was the small crank web, it's a simple component but I did want to try and achieve an attractive profile if possible



I thought mounting it on a purpose made fixture on the rotary table seemed the easiest way



Tap the fixture at 6mm.



With the part bolted down it's on to milling the raised boss



Then the tapering sides.



After a bit of filing the profile by hand it is fixed to the crank shaft using Loctite 638 and given a quick skim in the lathe.



I chose to turn the 4 columns next, these are made from 7/16 steel rod but need a slight taper cutting. I chose to adopt Jasons rather neat method of using a milling boring head as a means of offsetting a centre in the tailstock. I don't have a small revolving centre to fit the milling head but thought I'd make a crude dead centre and see how it goes.



With temporary centre hardened it's on to the columns by turning and threading one end and drilling the centre hole.



Turn down the other end to accept a thread later and hopefully allow a little flexing to turn the taper using the offset.



So far so good, seem to be getting a taper  :)





All that's needed now is to turn 3 more then move on to the entablature plate. This is made from 5mm thick steel with a large square central hole and various fixing holes. I chose to cut the centre hole first as I thought this would make it easier to hold for later operations.

6mm holes give radiussed corners.



Then mill out the centre.



Cutting radiussed corners at the front next





That takes me to this point





I did a it more work tidying up the bearing blocks and now reasonably happy with the result.



All in all it's now taking shape, I'd like to try and get the capitals for the columns and the base plate cut over the weekend  :)

Peter.





















« Last Edit: October 13, 2017, 07:18:09 PM by Gas_mantle »

Offline Ye-Ole Steam Dude

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Re: Building a Muncaster entablature engine
« Reply #53 on: October 13, 2017, 07:24:02 PM »
Nice looking parts, the finished engine should be beautiful.

Thomas
Thomas

Offline Jo

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Re: Building a Muncaster entablature engine
« Reply #54 on: October 13, 2017, 08:04:59 PM »
Hi Peter, that is coming on nicely  :). It will be on its legs and you will be in need of a flywheel shortly  ::)

A thought: the threaded end of the column looked rather thin where it was resting on the centre. In the past I have made a brass sleeve with a centre drill hole in the end to slide over threads like that to provide a bigger support surface and to avoid having to have a centre mark in the column.

And you have just reminded me I keep telling myself I am going to make a ball centre for supporting the ends when I turn tapers using a boring head  :Doh: One day I will remember, one day...

Jo
Enjoyment is more important than achievement.

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #55 on: October 13, 2017, 08:19:26 PM »
yes comming along nicely

I have been letting Peter get on with the making as he sees fit but I think he may well have put a 4BA thread onto the end of the 4.0mm dia column end as it looks a smaller dia than the unthreaded section. On mine I did the turning and trimming of the base and capital before cutting the threads to give max material around the shallow BS0 ctr hole, also specified metric Fine eg M4 x 0.5 on the drawings.





Yes it is a pity we can't locate any more of those curved spoke flywheels and the couple of possible alternatives are very spendy. maybe your supplier could get one recast from mine the next time he goes to the Foundry if it could go into a box with other parts?

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #56 on: October 13, 2017, 08:22:19 PM »
Thanks for the positive feedback  :)

I guess the treaded part against the dead centre is a bit thin (it's 4.1 mm for  a 3BA thread) but I only needed to take off about 3mm of the diameter at the narrow end of the taper and did it in small cuts. To be honest I was surprised the crude centre worked as well as it did - needless to say I kept it for future use  :)

I'm still struggling at getting a curved spoke flywheel so I think it's going to end up being straight, I can always swap it if an attractive curved one crops up later.

This evening I did have a quick play around making a tool to turn the decorative nuts for the columns but I think I'll need to keep experimenting till I can get the right sort of profile  :wallbang:

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #57 on: October 13, 2017, 08:25:24 PM »
make your form tool with a 9/32" radius curve.

Legs can be cut from 10mm stock which means only 2mm to come off diameter.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #58 on: October 13, 2017, 08:30:56 PM »
Hi Jason, you typed your message the same time as I did  :)

As you know I'm sticking to BA threads so I turned the ends at 4.1mm to be the same as the threads (with hindsight that may not be the best way) I was intending on using Loctite to secure the capitals and turn them to length if need be.

What size of hex did you make the decorative column nuts from ?

Thanks  :)

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #59 on: October 13, 2017, 08:40:53 PM »
1/4" or 4BA A/F (0.248") would do you nicely.

 

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