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Author Topic: A MH&B Topaz in New England  (Read 1521 times)

BESM

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A MH&B Topaz in New England
« on: February 15, 2023, 03:55:15 pm »

Greetings one and all.This is my first post to Mayhem though I have been reading and enjoying it for a while.Last year I bought a Topaz kit which was absolutely complete except for the engine itself. Clearly the priority was to acquire an engine but this proved difficult. 
I really wanted a 2 cyl slide valve design and these are hard to come by. The Oriental offerings are too big to fit the Topaz and suitable Cheddar and Anton engines seem impossible to find.So I decided to build my own, which is a close copy of the Cheddar Gemini with additional details from Malcolm beck's MB22 design. The bore and stroke are 3/8"x3/8".
The design was done in Solidworks and a drawing is attached.The engine has sealed ball bearings at every possible location and uses Oilite bushes elsewhere so that no external oiling is needed.The Maudslay gear works great and offers instant reversing at any speed.  This is really for emergencies.
The engine is now built and seems to run fine on air and steam as can be seen on my YouTube channel.
youtube.com/@70xke
Originally it used too much oil from an in-line displacement lubricator and I have now changed to an adjustable one connected into the valve chest. Also  I have made a throttle valve based on Malcolm Beak's design but using a more gradual shut-off to try and make the low speed running easier to control. Picture attached of it partially built.

The power plant is as designed by MH&B but I have decided to add a gas regulator to stabilize the boiler pressure at 40psi.Although there is not much space in the hull, the regulator should fit just forward of the oil separator tank.
I don't plan to write a build log as these have been done very well already and indeed I will be using them as a guide, particularly Jim Pope's work as well as that done by Wicksteed Park MBC.
About to start the hull build and my first query is why the instructions are to use body filler as an adhesive to glue in the shelves to the hull. 
My preference would be to use epoxy and I wonder if there is some subtle reason for using body filler.
I got a glimpse somewhere of a set of photos compiled by MH&B but can't now find them. If anyone has a copy of these I would be most grateful to get them.
Thanks for reading
Bruce MurrayWinchester MA
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Tim Logan

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Re: A MH&B Topaz in New England
« Reply #1 on: February 15, 2023, 04:45:33 pm »

Hi Bruce -
  Just cannot resist telling you how amazing that engine is and how awestruck I am by your skills. Cannot wait to see the Topaz operating at the lake! Simply amazing.
Tim
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rhavrane

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Re: A MH&B Topaz in New England
« Reply #2 on: February 15, 2023, 06:48:15 pm »

Bonjour Bruce,
I have watched your video and added my (very positive) comments on it.
I fully agree with you, Microcosm engines are quite big and my Topaz https://youtu.be/41D1iqEJ5L4 has an Anton 2 cm3 steam plant but Anton is retired  <:(
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Raphaël
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CliffW

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Re: A MH&B Topaz in New England
« Reply #3 on: March 25, 2023, 01:16:31 am »

I suspect part of the reason for the body filler is to provide some strength for the hull...I have an extra MB&H Topaz hull that has some very thin areas...so much so that since with shelf life the hull has been picked up many times there are a few lengthwise stress cracks in the hull...If I (or whoever gets this hull from me) build a boat with the hull they will need to provide some strengthening to the hull.  Without the interior framing the hull is very flexible and somewhat fragile.
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BESM

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Re: A MH&B Topaz in New England
« Reply #4 on: March 25, 2023, 12:40:52 pm »

That is an interesting idea about the need for body filler to strengthen weak areas of the hull. However I suspect that you would also need glass matting to provide the added strength.For myself I am already past the decision point and have essentially finished the hull. I did not see any obviously weak areas but there was one crack on the gel coat about 1" long which I will deal with when painting the exterior (soon).I used my favourite epoxy JB Weld to fix the prop shaft, engine and boiler mounts, following this I applied glass cloth for strength embedded in Zpoxy 30 minute version.
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BESM

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Re: A MH&B Topaz in New England
« Reply #5 on: June 02, 2023, 08:35:19 pm »

Well to close things out, I have finished the Topaz and it seems to run well - at least on the test bench.Maiden voyage June 11 at Tuscan Village Nashua NH.
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DBS88

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Re: A MH&B Topaz in New England
« Reply #6 on: June 02, 2023, 08:40:08 pm »

You have done a great job, a lovely boat and a well made engine
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Tim Logan

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Re: A MH&B Topaz in New England
« Reply #7 on: June 22, 2023, 11:35:21 pm »

 Bruce is too humble LOL. I saw the Topaz operating on its maiden voyage at Tuscan Village. She is absolutely elegant. There is no better word for it. Bruce's engineering and building skills are jaw dropping. I had a brief few seconds at the helm of the Topaz. Operating her "feels" elegant. She is something to behold. Well done my friend!
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KBIO

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Re: A MH&B Topaz in New England
« Reply #8 on: June 23, 2023, 07:53:11 am »

 :-)) Congratulations ! This is a pleasure to read and to discover your work !
Thanks for sharing.

BESM

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Re: A MH&B Topaz in New England
« Reply #9 on: June 23, 2023, 09:33:47 pm »

Thanks for the commentsI have posted a video here of its first runhttps://www.youtube.com/watch?v=vEzO7p_mM1Y
It ran well and did not need any ballast trimming.  I had an issue with the engine since after a second run, it began to run slowly.  I stripped the engine and found that there was too much steam oil inside the valve chest. I think this acted to throttle the engine - the admission ports are only 0.040" diameter.  After a thorough clean-out and rebuild it is back to its old self.  The displacement oiler I am using has an adjustable flow needle valve and even though I had it barely cracked open, the oil consumption was high. On strip down I found that even with the valve closed, there was a leakage. So the next runs will be with the needle valve closed
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KBIO

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Re: A MH&B Topaz in New England
« Reply #10 on: June 24, 2023, 10:33:00 am »

Hello !
This is classical !
Too much oil in the valves and this a good mayonaise maker ! I’ve seen oil can bigger tahtn the engine ! LOL!
No oil ? It works but the frictions takes a lot of power.
A tiny bit of oil inside the steam and you understand it all !
Think of a drop of oil fallen on the wet tiles of your kitchen … Slippery, isn’t ?? This is the best way to send you to the hospital with a broken fremur’s collar !
That is why .... we no longer steam up in retirement houses ! :embarrassed:


What grade oil are you using ?


You are a great trouble shooter ! :-))
Bye !
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