Author Topic: Another Westbury Wyvern build  (Read 20725 times)

Offline Roger B

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Re: Another Westbury Wyvern build
« Reply #105 on: September 20, 2019, 11:44:48 AM »
Splendid, sounds great  :praise2:  :praise2: you should be proud of that  :wine1:
Best regards

Roger

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #106 on: September 20, 2019, 02:21:29 PM »
Thanks everyone, the more I run the Wyvern, the happier I become with it. A small generator would make a good load for the little engine, any suggestions?

David
Don't die wondering!

Offline Roger B

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Re: Another Westbury Wyvern build
« Reply #107 on: September 22, 2019, 06:33:52 PM »
I have used small DC motors from the model making world as generators. My 25cc horizontal engine, a bit smaller than yours, has a model boat motor geared up 4-1with a toothed belt that will deliver 120W and will start the engine with a 12V battery. There is some stuff around here:

http://www.modelenginemaker.com/index.php/topic,2821.255.html

I am always happy to supply any more details that I can.

Best regards

Roger

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #108 on: September 04, 2021, 06:57:08 AM »
A very belated thank you to Roger for the generator info!

The Wyvern (along with the Mastiff) sat on a shelf for a long time and, whilst it was complete and working, it was a pain to get out and show running. This state also made the engines more likely to be discarded when I'm no longer around to run them  (I have to think about this more at my age as I've lost three friends in the last three years and now there's another with cancer of the pancreas). The task then was to take the bare engine and package it up with its own ignition, fuel and coolant on a stable, portable, base

As an addition there was a clear need for better balancing which I'll describe first. The kit of bits from Hemingway included a copy of a letter from Model Engineer for July 1966 from Roland V. Hutchinson of Michigan where he described the need to increase the size of the flywheel rims (which I did during the build) and to add to the crankshaft balance weight. The letter gives dimensions for the extra weights but it was worth checking if only to learn more about balancing, something I hadn't done before. I stripped out the conn rod and piston, weighed them as described in many places and came up with a calculated balance weight a good bit less than that found by Mr Hutchinson. This needed checking so I made up two arcs of steel to my weight and superglued them to the crankshaft:



The "knife edges" were improvised from box-cutter blades, magnets and a drilling vice.
The weights checked out nicely and all I can think is that Mr Hutchinson was working with a cast iron piston - a weight estimate from Alibre (not always reliable...) for a CI piston showed that this was likely so I drilled and tapped for securing screws:


and put it all back together.

The finishing off included a simple hardwood and thick ply base, Minimag ignition and battery. Fuel and coolant tanks were fabricated and put on 3D printed stands:





The tool kit now has a starter to go in a cordless drill and fuel measure and funnel printed in PETG which seems to hold up well with use.

The balancing, helped by the extra mass of the timber base, has made to engine much easier to keep in one place. Only at higher revs does it start to move about:

[youtube1]https://youtu.be/lHORT2W_Ol4[/youtube1]

I've shown our daughter how to get it running (she's living with us while her house is being altered) and, if we ever get out of this damn lockdown, I'll show the two boys as well. After that its over to that generation.

Thanks for following along and for all the help!

David
Don't die wondering!

Offline john mills

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Re: Another Westbury Wyvern build
« Reply #109 on: September 04, 2021, 09:33:50 AM »
the engine looks and runs great.
I know the lock down is dragging on but i guess it is better locked down as hard as it can be is better than getting
out and about and coming in contact with this virus and catching it .it seams it is about in lots of places now it has been close to my place.
stay as safe as you can hopefully it will get better before long.
John   

Offline cnr6400

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Re: Another Westbury Wyvern build
« Reply #110 on: September 04, 2021, 12:07:43 PM »
Your engine's looking great David! Beautifully made and finished. Base and info plates are top notch too. Congratulations.  :ThumbsUp: :ThumbsUp: :ThumbsUp: :cheers:
"I've cut that stock three times, and it's still too short!"

Offline MJM460

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Re: Another Westbury Wyvern build
« Reply #111 on: September 04, 2021, 01:29:39 PM »
Hi David, that really nicely done.  Those finishing touches really make a difference.  I like the timber base and the inclusion of a battery voltage meter.

It sounds like the balancing was also an improvement.   Part of the issue is that the balance weight not only has to be appropriate mass, but also the right distance from the crankshaft centre line.  Also, any attempt to balance the reciprocating forces due to the piston is only achieved at the expense of introducing a reciprocating vertical force, so the result involves a compromise.  As you mentioned, at least the mass of the timber base helps reduce the vibration amplitude due to the vertical force.   It sounds like you achieved a good result.

A very productive use of some lockdown time.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Admiral_dk

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Re: Another Westbury Wyvern build
« Reply #112 on: September 04, 2021, 07:40:46 PM »
Fantastic end result - looks, sounds and runs well  :cheers:

Offline Don1966

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Re: Another Westbury Wyvern build
« Reply #113 on: September 06, 2021, 01:04:51 AM »
Great finish and runner….. :cheers:


Don

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #114 on: September 06, 2021, 12:13:20 PM »
Thank you all,
john, Don and admiral for the encouraging comments, I'll show something similar for the Mastiff engine soon hope you like that as well.

 cnr: I'm not really a woodworker so I'm quite pleased that the plinth worked out as well as it did. The engraved brass plates were made on a home-brewed CNC mini-mill, getting that working took far more hours than it may ever actually be used :noidea: .

MJM: It isn't possible to get "perfect" balance in a single (at least without using an auxiliary balance shaft) so there is always a compromise. Before the balancing effort, and just clamped to a piece of ply, Wyvern dithered all over the place at any RPM; now it stays in one place until it gets to higher revs. I tried to use my smartphone accelerometers to measure the difference in vibration but I don't know how to work out the properties of a suitable substrate, or how to couple the 'phone to the engine. It would be really cool to see the z component start to rise as the balance weight gets too large. This would be worth pursuing, but not right now!

David
Don't die wondering!

Offline steamer

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Re: Another Westbury Wyvern build
« Reply #115 on: September 06, 2021, 12:25:26 PM »
I'm late to the show Dave, but that is a wonderful presentation of a great running little engine.   Nicely done sir!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #116 on: September 06, 2021, 11:30:06 PM »
Thank you Dave,
I'm pleased you like it.
Next stop is to finish off the Mastiff the same way ans make progress with the big Corliss engine.

David
Don't die wondering!

Offline MJM460

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Re: Another Westbury Wyvern build
« Reply #117 on: September 08, 2021, 11:56:40 AM »
Apologies, David, you clearly didn’t need extra information from me on balancing.

Do you have an Ap that allows you to read those accelerometers?

For coupling to the accelerometers, I wonder if some variation of the old “ screw driver (handle) in the ear” trick would work.  So many possibilities with the sensors available in these phones.

MJM460

The more I learn, the more I find that I still have to learn!

Offline deltatango

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Re: Another Westbury Wyvern build
« Reply #118 on: September 09, 2021, 05:28:03 AM »
MJM, extra information is always welcome!

The app is called "Physics Toolbox Suite" and will display x,y,z accelerations, angles, sound pressure levels, measure sound frequency, generate tones, has an audio spectrum analyser, light and colour measurements, magnetic fields and others. It's great fun and occasionally useful.

Attaching the 'phone to the engine bed just needs a well made and secure clamp. The problem with measuring the accelerations in three axes is minimising the noise generated by the engine+block moving around. Clearly it has to be able move else there are no accelerations but if it can rattle against anything (e.g the bench underneath) then this creates unwanted noise. Maybe a sheet of rubber/plastic underneath? Absolute measurements may not be necessary, relative numbers for comparison may be all that is needed - or possible.

David
Don't die wondering!

Offline Charles Lamont

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Re: Another Westbury Wyvern build
« Reply #119 on: September 09, 2021, 08:38:24 AM »
+1 on the Physics Toolbox Suite phone app.

 

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