Author Topic: Building a Muncaster entablature engine  (Read 23040 times)

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #30 on: September 19, 2017, 07:49:27 PM »
I meant to say the big horizontal I'm wanting to start next year will be 24m bore  ;)

Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #31 on: September 19, 2017, 09:55:03 PM »
FWIW, my practice is to drill the piston rod hole in the cylinder cover with it attached to the cylinder after finding the center of the cylinder bore.  Same again for the gland.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #32 on: September 19, 2017, 10:10:26 PM »
Thanks Kvom I hadn't thought of doing that but it's something to consider next time  :)

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #33 on: September 20, 2017, 04:46:06 PM »
I've now managed to drill the cylinder and cover but seemed to make hard work of it and I'm sure the way I did it wasn't the easiest but here's how I tackled it.

First I made a close fitting threaded plug to hold the cylinder cover down and stop it rotating while drilling. I guess this is overkill but I had a piece of scrap round stock to hand that only needed a couple of minutes work so I thought it worth doing.



I don't have a fancy DRO with PCD functions so it's time to dust off the rotary table and get it centred under the spindle. The co-axial indicator makes it a 2 minute job  :)



With the table centred and it locked in position I centre the cylinder using the same method, although not difficult I found this fiddly and time consuming.



Time to fasten down the cover and give it all a quick check again using the co-ax indicator. I also set the cylinder port face inline with the x axis of the mill.



I'm using 7ba studs so I need 6 2mm holes drilling and the cover opening out to 2.5mm clearance. All that's needed now is to move the mill X axis to drill 4.5mm from the outer edge and rotate 60o between holes.



After doing all 6 then tapping the cylinder I have this.



I'm pleased with the even spacing and they are at the right radius but they are slightly rotated anti clockwise from what I wanted so are slightly off parallel to the port face :(



I guess it's not a lot out but still a bit annoying  :(

Peter.







Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #34 on: September 20, 2017, 10:36:57 PM »
After seeing this thread and the Westbury article about it, I decided to model it myself in Solidworks  using the imperial dimensions.  Discovering some of the "hidden" dimensions like the length of the conrod is an interesting exercise.  I don't know if I'll build it myself in metal, but it's a fun build with electrons.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #35 on: September 20, 2017, 10:41:37 PM »
I'd be interested to see that  :)  I think it's an attractive engine considering it's fairly simple.

Offline b.lindsey

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Re: Building a Muncaster entablature engine
« Reply #36 on: September 21, 2017, 12:13:46 AM »
Nicely done Peter. It's not out if parallel by much. Shouldn't present a problem and hardly noticable on the finished engine.

Bill

Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #37 on: September 21, 2017, 03:09:56 AM »
The 6 holes are fine for the bottom.  For the top cover you have the guide bars aligned with the bolt holes, so make sure the bolt circle is large enough to clear the bolt heads and the bars.

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #38 on: September 21, 2017, 07:31:40 AM »
No bolts on this engine, all studs and nuts and there was enough room for me to get the small head metric nuts in.

Peter when you come to machine the two flats for the guide bars as the PCD is a bit off it would be best to clock your vice true and then hold the cylinder with port face against the fixed jaw, screw on the cover and mill it while fixed to the cylinder. You need a small dia cutter for this to avoid hitting the edge of the recess.

Kvom, yes it's good doing it in CAD, I spent quite a while fine tuning the conrod and guide bars to make sure nothing hit as the engine rotated. be interesting to see a 3D image of your engine.

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #39 on: September 21, 2017, 08:24:18 AM »
Thanks guys.

Jason, thanks for the tip off, I think for the time being I'll leave milling the flats until I have made the guide bars and possibly got the cylinder fastened down. I'm a bit gutted that the PCD is slightly out as I did align the assembly before drilling but obviously I wasn't accurate enough  :(

I'll make a start on the steam chest next.


Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #40 on: September 21, 2017, 12:22:12 PM »
Given the lack of dimensions on Muncaster's drawings, one has a good bit of freedom in designing the sizes of the cylinder gland and hence the separation of the guide bars and thus size of the crosshead.  I should have a good 3D image to post later today.
« Last Edit: September 21, 2017, 05:58:19 PM by kvom »

Offline Florian Eberhard

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Re: Building a Muncaster entablature engine
« Reply #41 on: September 21, 2017, 06:31:26 PM »
Hey kvom

Correct me if I am wrong - but I think you have got a collision included in your model! The screws of the upper cylinder cover will be very difficult to put there because I think they would touch the crosshead-guiding rails! Especially if you would screw them to the cylinder cover sideways.

And Peter; you could still rotate the hole pattern for  half the division. (to what was planned) The screw which would be on top of the transfer port could be screwed into the cylinder cover, I think five of six screws will hold the cover thight enough. 
But nice work on that cylinder otherwise!

Florian

Offline Gas_mantle

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Re: Building a Muncaster entablature engine
« Reply #42 on: September 21, 2017, 06:38:15 PM »
Thanks Florian  :)  As the holes are only slightly out and they probably be hard to notice in the completed model I'll probably leave them.

It looks like Kvom has got the cylinder cover holes orientated right but they look to be on smaller PCD - the cover should be larger than the cylinder and have a decorative recess.

Offline kvom

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Re: Building a Muncaster entablature engine
« Reply #43 on: September 21, 2017, 07:02:02 PM »
Hey kvom

Correct me if I am wrong - but I think you have got a collision included in your model! The screws of the upper cylinder cover will be very difficult to put there because I think they would touch the crosshead-guiding rails! Especially if you would screw them to the cylinder cover sideways.

Yes, I discovered that before and mentioned the problem in a previous post.  I positioned the holes to screw into the cylinder walls rather than through the flange.  I am just going to move those two holes away from the bars.

Offline Jasonb

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Re: Building a Muncaster entablature engine
« Reply #44 on: September 21, 2017, 07:39:10 PM »
This is the 3D image of most of the parts assembled from my working drawings


 

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