An improved cylinder block ?

[SAE140]

On a tour of Ebay recently, I was struck by just how many powerheads were for sale - but always sans their Cylinder Block. From this I think it's fair to conclude that one less-than-optimal design feature of the Seagull is internal corrosion and marine concretion build-up within the water jacket, especially with the square blocks.

I had a quick ferret around, to find a rather nice looking 110cc water-cooled block at:
http://www.aliexpress.com/product-fm/33 ... alers.html
Ok - it's simpler, being a 4-stroke - but the price is superb at $26 for 1, or $16 each for 10.

If this quality and pricing is reasonably typical for this kind of machined casting, it strikes me that there could be a case for sourcing some square blocks from China ?

So as not to offend vested interests - does anyone know roughly how many spare blocks are currently still in existence ?

It also occurs to me that it would be rather neat if a block could be made with a removable outer water jacket, to enable internal inspection and cleaning. A tad more difficult to engineer with a 2-stroke in view of the porting, but I'm sure not impossible. (Very clever, these Chinese)

Any opinions on the possible market size, or anything else for that matter ?

[charlesp]

I don't know how many Century blocks are held in stock by British Seagull, they did have some made fairly recently. They are, of course, a lot more expensive that £16.00, I suspect the Chinese manufacturers made lots and lots of the ones you have seen.

The ones that go most often seem to be the Silver Century blocks, you're quite correct that there are a number of power heads without cylinders around.

The inspection and cleaning isn't too much of a problem; with the head off you can get at all the areas you need to chisel the clag away.

[Charles uk]

I'm told B.S. sell 8 to 10 new cylinders a year for £157 inc.

Was it you who was a toolmaker? as this strikes me as a perfect job for a cast iron liner with accurately machined in ports with a cast aluminium water jacket

[SAE140]

I'm told B.S. sell 8 to 10 new cylinders a year for £157 inc.

Ouch

Was it you who was a toolmaker? as this strikes me as a perfect job for a cast iron liner with accurately machined in ports with a cast aluminium water jacket

Not guilty (wish I was) - very much a make-do-and-mend 'bush' engineer these days ...

Interesting you mention aluminium - I found one manufacturer who produces water-cooled motorcycle cylinder blocks in ceramic-aluminium. Apparently this stuff is really hard (can even be used to make knife blades), and completely immune to corrosion. They also have a minimum order of 100 for custom jobs - whereas the cast-iron guys have a 300 minimum.
http://www.alibaba.com/product-gs/23734 ... ramic.html

Their prices for established designs are very cheap, but heaven only knows what their tooling costs are for custom work. Only one way to find out ...

I have to say I've got next to zero knowledge of using ceramic in engineering, but it all seems very appealing.

[Charles uk]

When you talk to them ask if it's suitable for cast iron rings.

Early Seagull sports had Nikasil lined cast aluminium cylinders but these ran "chrome" rings.

[SAE140]

When you talk to them ask if it's suitable for cast iron rings.

Early Seagull sports had Nikasil lined cast aluminium cylinders but these ran "chrome" rings.

Good thinking - Briggs and Stratton do something similar to their ally cylinder bores.

Well - I've sent off 4 enquiries - 2 to China (one ceramic, one Cast Iron), and 2 to India (both Cast Iron).
Plenty of guys casting man-hole covers in India, not so many precision engineers.

[Charles uk]

Seagull cast their most long lived cylinders, pre mid 60's from what was termed in the foundry business as gutter iron i.e. a material that was ideal for thin section castings & didn't corrode too readily in very wet conditions.

[Charles uk]

Which cylinder did you take you drawings from, for these enquiry's ? as it's probably the WS silver century cylinder that appears to be the most in demand.
Are you planning on getting them to machine them or do you envisage paying English prices, give some thought to changing the cylinder threads to metric as stainless M6 studs & M8 head bolts are way cheaper than steel BSF ones, & would be reflected in their tooling costs.

I'd be very interested in the outcome.

[SAE140]

Which cylinder did you take you drawings from, for these enquiry's ? as it's probably the WS silver century cylinder that appears to be the most in demand.
Are you planning on getting them to machine them or do you envisage paying English prices, give some thought to changing the cylinder threads to metric as stainless M6 studs & M8 head bolts are way cheaper than steel BSF ones, & would be reflected in their tooling costs.

I'd be very interested in the outcome.

What I've done - rightly or wrongly - is to describe the casting and have enquired about 'typical' costs for machined castings of this type, as all I want at this stage is a feel for the costs involved. Depending on their response, I'll be supplying further details on request.

What I plan to do (and have advised them accordingly) is that to avoid any language difficulties, I would supply them with an actual cylinder block to copy. (That way they can draw up their own diagrams annoted in their own language, and there'd be no excuse for any measurement errors.)

Indeed, if the project really is financially feasible, then I rather fancy taking myself off to the country of manufacture taking the sample block (+ piston) with me, and see for myself how these guys operate. A kind of 'engineering holiday'.

So first - a feel for the costs and quantities involved. If this makes sense, then I guess I'll need to approach the current trademark holder for permission to include the wording 'British Silver Seagull' on the block side. Then take it from there ...

I agree with you about using metric studs.


Manifold - I'll PM you off-forum - any information of the 'be warned' type has to be a good move. I have some friends in Goa who I was thinking of using as intermediaries if the Indian foundries looked good - but I'm all for learning from the experiences of others..

[charlesp]

Don't know how you would get on with British Seagull giving permission to use their trademark when you're effectively attempting to undercut one of their existing products.

One thing that could definitely find a market if you could source a good supply - that's brass tanks. They if anything are the most difficult component to find and very time consuming to restore.

Most of the people who need a new block find one on eBay or from a donor engine if they don't want to buy a new one from B.S.

[Oyster 49]

Hi Charles, I think a replacement steel(zinc plated of course) or brass tank for the 102 could also be an oppurtunity. As a pattern part you could even go down the cost reduced route and (purist scream now!) put flat ends on it. It would keep tooling/set up charges down.

As a pattern replacement for something that British Seagull don't sell, then it would not undermine anything.

25 years ago I owned an MG midget, the MG owners club did a similar thing with hoods, they called it the "club hood" or similar. It was basically a budget item, but slightly better than the original, but cheaper.

[Charles uk]

140

The sample block might well cause some problems.

Seagull cylinder blocks seem to have quite wide tolerances, if you take 6 identical (models) cylinders & measure them you will find many differences while the bores will will all be within 3 thou in diameter depending on wear, the port locations & sizes are all over the place up to 60 thou differences & the overall lengths seem to vary by quite a bit.

If you take these 6 cylinders & test them one or two seem to perform far better than the rest, how do you know which one is right?
The normal course of action for this type of endeavour would be to provide an engineering drawing with a the permissible tolerances noted & the exact cast iron mix specifications, so that both parties know the rules.

In this country I can see £65 to £80 worth of machining on each cylinder in quantities of 100 not counting the costs of any fixtures that would be required, when you add that to the pattern costs & the core moulds that would be required by the foundry it starts to make Seagulls price look quite reasonable.

[charlesp]

The competition for these items (blocks, tanks) is of course the second-hand market. That can happily supply blocks, but the tanks are a different matter.

I think it would be worth making 102 and oval type tanks, and it would be worth going for the original shape. Remember it's not difficult to find a 102 tank, but it is difficult to find one that's not beaten up. I reckon there would even be a market for plastic replacements.

[SAE140]

140

The sample block might well cause some problems.

Seagull cylinder blocks seem to have quite wide tolerances, if you take 6 identical (models) cylinders & measure them you will find many differences while the bores will will all be within 3 thou in diameter depending on wear, the port locations & sizes are all over the place up to 60 thou differences & the overall lengths seem to vary by quite a bit.

If you take these 6 cylinders & test them one or two seem to perform far better than the rest, how do you know which one is right?
The normal course of action for this type of endeavour would be to provide an engineering drawing with a the permissible tolerances noted & the exact cast iron mix specifications, so that both parties know the rules.

I don't disagree with what you're saying - but I don't have the measurements for the definitive 'best case' block, I don't know what the permissible tolerances are, nor the optimum grade of cast iron to be used - hence any engineering drawing submitted at this stage would be a work of fiction. If anyone can assist with remedying these deficiences, it would be appreciated.

The trademark issue is something to be considered - if these blocks are 100% cast iron, then I agree, nothing has been achieved except possible undercutting of price (which has yet to be determined, anyway). Perhaps the only really worthwhile methodology is to opt for ceramic or hybrid (cast-iron liners within an ally jacket). Right now it seems that determining the precise measurements of the definitive block is the key issue, and I haven't a clue re: how to go about achieving this.

Have just found: http://www.2-stroke-porting.com/Computer_Design.html who could be helpful.

[Charles uk]

Have a search on the web for pressure diecast aluminium, the technology required might explain why Seagull never moved away from crude cast iron cylinders, & have a look on this site for A Graham Bell's book on two-stroke performance tuning as I think it contains the details of how to measure the ports on 2 stroke cylinders.

I doubt there is the demand for an improved Seagull cylinder, when most Seagull owners are fully aware that you can buy several working Seagulls for the cost of a new cylinder, a full gasket set & a pair of piston rings.

We're a tight bunch.