Author Topic: 15cc Seal Help  (Read 9240 times)

Offline steamer

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Re: 15cc Seal Help
« Reply #75 on: March 11, 2020, 04:55:07 PM »
Hello Jason,

That's exactly how I would tackle the water jacket if I decide to machine from solid.

I used the same Woodruff cutter technique on the Mercury's propeller hub. It would be easier to handle the chip clearance on the Seal as there is a through hole and also space in the adjacent cylinders



I will wait and see what Kirk delivers before I decide which way to go. I have not played 'find the part in a casting' before, It could be interesting.

Mike

That will depend greatly on the casting my friend!....Bon chance!
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline gadabout

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Re: 15cc Seal Help
« Reply #76 on: March 11, 2020, 08:09:59 PM »
If I was going to build one from a billet I would incorporate the mounting lugs into the front and rear bearing housings I think.
Mark

Offline Vixen

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Re: 15cc Seal Help
« Reply #77 on: March 11, 2020, 08:39:49 PM »
If I were to build this engine from scratch using billet material, I believe there is a very big danger of adding so many little design changes that the end product would be a completely different engine to the intended Westbury Seal. At least using the Hemingway castings will keep me honest to the original. (warts and all)
Mike
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Sometimes, it can be a long and winding road

Offline gadabout

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Re: 15cc Seal Help
« Reply #78 on: March 16, 2020, 07:55:48 AM »
Mike,
Any news on the castings yet? Must be due soon!
Mark

Offline Vixen

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Re: 15cc Seal Help
« Reply #79 on: March 16, 2020, 09:42:02 AM »
Hello Mark
No, not yet. A lot of things have changed in the world since we started this topic. Europe and the UK are shutting down and isolating. Times, they are a changing

Mike
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Sometimes, it can be a long and winding road

Offline gadabout

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Re: 15cc Seal Help
« Reply #80 on: March 18, 2020, 02:02:57 AM »

ChuckKey

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Re: 15cc Seal Help
« Reply #81 on: March 21, 2020, 05:54:02 PM »
At the Hemingway website, Kirk says it is pretty much business as usual, atm.

Offline Vixen

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Re: 15cc Seal Help
« Reply #82 on: March 21, 2020, 06:05:44 PM »
I talked with Kirk during the week. He says they are busier than usual, because people are at home and now more time on their hands and are placing more orders.

The non ferrous foundry have just finished the latest batch of castings, they will be sent to Hemingways next week for onward distribution. Hopefully, I will be getting my 'Seal' castings soon

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

ChuckKey

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Re: 15cc Seal Help
« Reply #83 on: March 21, 2020, 09:35:39 PM »
Vixen, while you are re-drawing in CAD, I suggest you have a look at the cam profiles and tappets. The cam profile dimensions do not quite fit together as designed. Good enough for a 10:1 scale paper and compass exercise, which is what ETW would probably have done. For precision, one dimension has to be adjusted a bit, the base circle, cam angle, flank radius, nose radius, or lift. For example, if you leave all the other dimesions the same, the inlet cam nose radius is close to 1/64, not 1/32.

More importantly, in most cases, you will find that the inlet cam in particular 'falls off the edge' of the tappet at the point of transition between the flank and tip radii. This is the point at which the contact line between cam and tappet is at its greatest distance from the tappet center, and is therefore also the point of maximum velocity of the valve.

My Seagull has exactly the same design and exactly the same problem. I resolved mine by fattening the inlet cam angle a little to get the nose radius closer to the design 1/32,
and by increasing the tappet diameter to 9/32.   

Offline Vixen

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Re: 15cc Seal Help
« Reply #84 on: March 21, 2020, 11:57:08 PM »
Hello ChuckKey,

Thanks for the 'heads up' regarding the cam profile and tappet diameter issue. I will look into this in more detail during the week.

Having read through ETW's  1947 Model Engineer articles several times, it becomes fairly obvious that ETW had not in fact build a 'Seal' engine at the time of writing. The photos of the part completed engine are attributed to Mr R C Martial and the completed camshaft to a Mr N A Leach. Hence the numerous dimensional errors and the cam/tappet design error, you refer to, were not picked up at the time and only discovered by later generations of model engineers when they attempted to build the engine. Fortunately several of ETW's designs had feature in common and lessons can be learned from all his designs.

So, thanks to you, many of the drawing and design errors are being identified, which can only improve current and future builds of this popular little engine.

Thanks again

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Vixen

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Re: 15cc Seal Help
« Reply #85 on: March 29, 2020, 01:23:41 PM »
I just heard from Kirk at Hemingway's They are still open, running their business from home. It's business as usual, while stocks last.

Unfortunately for me, the 'Seal' castings did not come out of the foundry in time. The foundry cannot get supplies of fuel oil or green sand and has closed down.

Stay In,  stay safe

Mike

« Last Edit: March 29, 2020, 07:07:59 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Vixen

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Re: 15cc Seal Help
« Reply #86 on: April 25, 2020, 08:25:09 PM »

I had a pleasant surprise today. A box of castings arrived on the doorstep, in a box marked 'Hemingway'. Inside were the long awaited cylinder block and cylinder head castings for the 15cc Westbury Seal. Kirk from Hemingway's informed me, at the beginning of March (beginning of lock down), that his non ferrous foundry had been forced to close due to lack of fuel oil and greensand. They overcame the delivery problems and were back in business about two weeks ago. My castings were top of the list and Kirk was able to deliver them through the post.

These are my first ever engine castings. They look very nice, the crankcase is overlength by 0.25 inches, which I was told to expect. That's a bit of a shame, as it means the attractive raised flanges at both ends will disappear when the crankcase block is machined to dimension.

Jo always talks about fondling her castings. Now I know what that means, it's a process of inspecting and measuring the raw casting from all directions to decide precisely where the engine part is located within the oversize casting.

Not sure when I will make a start because we are still heavily committed to supporting our National Health Service workers by making the stuff that makes their lives a little easier. Currently the nursing staff are crying out for comfort clips which are intended to take the pressure of a surgical mask’s elastic straps off the back of the wearer’s ears. They stop painful chafing.  Simple things can make such a difference.

Stay strong, this storm cannot last forever.

Mike


It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline gadabout

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Re: 15cc Seal Help
« Reply #87 on: April 25, 2020, 10:37:16 PM »
Mike, that's some good news re the castings arriving! But we need pics for proof!!
Mark

Offline Jo

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Re: 15cc Seal Help
« Reply #88 on: April 26, 2020, 06:52:51 AM »
Pleased to hear they have arrive Mike  :)

 :pics:


Jo always talks about fondling her castings. Now I know what that means, it's a process of inspecting and measuring the raw casting from all directions to decide precisely where the engine part is located within the oversize casting.


 :embarassed:

Jo
Enjoyment is more important than achievement.

Offline Jasonb

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Re: 15cc Seal Help
« Reply #89 on: April 26, 2020, 07:11:21 AM »
Is there sufficient excess thickness at the ends to be able to machine to overall length and then take a bit more off to reinstate the bosses or is the inside cavity also oversize resulting in a lack of material?

 

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