Westbury Sealion

This topic has 14 replies, 7 voices, and was last updated 2 February 2015 at 14:52 by frank brown.

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1 February 2015 at 11:21 #178028
Jesse Hancock 1
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@jessehancock1
Hi guys I have recently started a Sealion by Mr E.T. Westbury to power a Tank I was contemplating.

One of the things which has always bothered me has been collecting suitable materials for a project hence the kit.

The other worry I have is with the design of the crank it's self. I am thinking of changing the configuration as it looks to me as though the engine must have inbuilt vibrations due to the shape of the crank.

So to my question: Has anyone here built this engine to spec and drawn any conclusions about vibration pertaining to the cranks configuration?

Jesse.
Advert

1 February 2015 at 11:21 #23695
Jesse Hancock 1
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@jessehancock1
Happy with the crank?
1 February 2015 at 12:24 #178034
Lars-G Kjellander
Participant
@lars-gkjellander17135
Hi Jesse, I have a kit of the Sealion I intend to build some day, but in the meantime I found on "The Internet Craftmanship Museum" website a group build of The Seal 15cc engine. Not the same but the same type of crankshaft so maybe you can find a clue on there **LINK** I have not read it myself, but there is some nice pictures.

Good Luck

Lars
1 February 2015 at 13:14 #178042
JasonB
Moderator
@jasonb
Where do you see the problem? the two rising pistons will basically balance out the two falling ones as its a 180degree crank
1 February 2015 at 14:06 #178046
frank brown
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@frankbrown22225
On the contrary, when the two outer pistons are rising, the two centre ones are falling, this will flex the crankshaft in the centre. Could be OK if a centre crankshaft bearing is fitted. If you want to redesign it, here is a good article :- http://www.epi-eng.com/piston_engine_technology/crankshaft_design_issues.htm http://www.epi-eng.com/piston_engine_technology/crankshaft_design_issues.htm

Clickable link added.

Frank

Edited By John Stevenson on 01/02/2015 16:16:54
1 February 2015 at 14:34 #178052
Jesse Hancock 1
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@jessehancock1
Thank you Frank and Lars. I think I have seen the video but this time I'll book mark it for easier access.

Frank my thoughts exactly… My father was fond of Austin/Morris A series engines but on tuning then he always had trouble knocking out big ends and mains due to lack of bearings = whip in the crank.

Jason I might be worrying overly much but I take your point. Perhaps two cranks and cams are in order and see which works best.

Lars I have met other men and conversed over the net with them in Holland. Are you Dutch by chance?

Jesse.

PS: Got the pages book marked. I suppose we shouldn't forget that Mr Westbury was trying for ease of build and economy here and so this could have been his major concern and the reason he made the crank out of flat. Just thinking out loud.

Edited By Jesse Hancock 1 on 01/02/2015 14:45:40
1 February 2015 at 16:04 #178059
FMES
Participant
@fmes
Posted by frank brown on 01/02/2015 14:06:10:

On the contrary, when the two outer pistons are rising, the two centre ones are falling, this will flex the crankshaft in the centre.

Many older vehicles were built with this crank design and it seemed to work ok, I think the Austin 7 was one and I have Coventry Climax sidevalve that only has two main bearings.

They were never stressed enough to cause a problem.
1 February 2015 at 16:31 #178062
JasonB
Moderator
@jasonb
The sealion has a central bearing so no whip

Edited By JasonB on 01/02/2015 16:36:40
1 February 2015 at 17:01 #178067
JasonB
Moderator
@jasonb
Jesse, I don't think economy of materials had anything to do with the shape of the crankshaft. On several of Westbury's models the crank starts off as a round bar as it is generally easier for hobbiests to get hold of metals like EN24T in the round which can then be machined to a flat section and then turned to form the crank, a bit like this one of mine.

Malcom Stride covered crankshaft design pertaining to model engines over about 3 or 4 installments of "IC Topics" worth having a read through to see how things affect our little engines.

EDIT

Before you try making one out of round stock with balance weights it may be worth reading this!

Edited By JasonB on 01/02/2015 17:37:29
1 February 2015 at 18:31 #178075
Jesse Hancock 1
Participant
@jessehancock1
Well I don't know what to say here but I can assure you my Father had trouble a plenty with both Austin seven and the 'A' series engines when it came to knocking out big ends. I can't argue the reasons why as this may be as varied as the weather.

Reading again the instructions it says that the casing will NOT accommodate circular crank webs as the body is too narrow. Which may negate my enquiry altogether.

For the record Wesbury uses flat bar on this crank from which I gather he roughed out using a saw, and then stress relieves the piece in the normal way.

Thanks for replying lads.

Jesse
1 February 2015 at 19:03 #178082
Neil Wyatt
Moderator
@neilwyatt
ETW once wrote a long explanation of why the extra complexity of a centre bearing was not required for the Seal and related engines.

I think he got rather fed up of people telling him it needed one and pointed out the large numbers of Seal engines built that had no signs of problems from crankshaft distortion…

Neil
1 February 2015 at 19:43 #178086
John Stevenson 1
Participant
@johnstevenson1
I think the difference here is load.

On an Austin 7 for it's day it was expected to be a work horse, even pulling mother in law about would get you an overload ticket these days.

Oils were nowhere near as good.

Now take the seal lion and other model engines. I dare say none of these ever ran 40 hours max in their whole lives so it's really comparing apples to oranges.

As regards big ends I did read an article some years ago about tuning these for racing and the recommendation was for the outside edges of the shells on No's 2 and 3 to be scraped to give a barrel shape to the shell to prevent rubbing when the crank did bend. No's 1 and 4 were recommended to only have the inner sides scraped.

Makes a lot of sense when you think about it and obviously the racing guys had learn the hard way but I bet this info was never passed on to the general motoring public.

Many many moons ago when Milton Keynes was only fields we used to run a fleet, OK small fleet, 7, Moggie Minor vans with the 803 OHV valve engine. These were always bought decent second hand then abused just short of the Geneva Convention. It was good one that managed 9 months before running a crank. We got that good at it that two guys could do one, engine out, strip, new crank and bearing and back in, in just under 3 hours.

Once we moved onto the 998cc OHV thousand engine we hardly had any engine problems
1 February 2015 at 20:36 #178097
FMES
Participant
@fmes
Posted by John Stevenson on 01/02/2015 19:43:23:

We got that good at it that two guys could do one, engine out, strip, new crank and bearing and back in, in just under 3 hours.

Takes that long to disconnect all the sensors these days
1 February 2015 at 20:50 #178099
Jesse Hancock 1
Participant
@jessehancock1
You may be right Neil as like I said I have his destructions here but looking at the casting it's probably the weir across the centre of the main block casting which stops the introduction of circular webs into the casting.

However my question was about vibration all the while expecting that not too many people have made this engine and therefore there wouldn't be much response. Gets the old brain ticking though aye?

When in OZ the front of our patch of dirt used to resemble a second hand car lot with my dads mates and perhaps some of his none mates dismembering all kinds of cars. There were discussions going on in various veins about how this or that should be done. Most of the cars I remember back then were either Holdens or Eliott Ness style rag top jalopies resembling covered wagons more than cars. Old style forum too I guess.

Jesse.

John yes you can imagine the abuse the old Austins etc got in Oz. OIL! what's that cobber?

Edited By Jesse Hancock 1 on 01/02/2015 20:54:30
2 February 2015 at 14:52 #178173
frank brown
Participant
@frankbrown22225
Totally off topic :- A mate of mine told me that in the 50s, their Austin 7 was suffering from terrible pinking. So he and his dad took the head off, only to discover that one piston was made of wood !!!. Some thing to do with the war austerity regime?

Frank
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