Making a 10cc Whippet pattern

[bmac2]

I got the pattern for the “loose piece” worked out (I think) and got everything glued up. All that’s left is to form the fillets on all the edges and sanding so I have no sharp corners. The glue has set and the little beast is starting to look like something. I must admit I’m tempted to pour the block solid but I just see nothing but shrinkage problems and this is supposed to be my exercise in pattern making.

 

[bmac2]

In CAD this was easy a few round bits on a basically square bit. Now I’ve made the jump from the cyber space onto the meat world and things got difficult. I need to make a negative mold to get a positive cast of the sand core so I’ll have the correct negative (hollow) in the engine casting. This is what I want to end up with.

 

[bmac2]

You just have to love the warm feel you get from real wood siding, and stain, and ladders. Despite that I got a chance to sneak away from painting the house over the weekend and got some work done on the core mold. Coming up with a plan for the basic mold shape was piece of cake. Coming up with a plan for a mold the correct size that I’ll be able to get the sand core out of . . . without breaking it, was a different ballgame. After slicing it up in CAD for the last week or so and I think I have a plan that’s worth giving a try and got some wood sized and cut down to what I needed.

 

[bmac2]

Then I temporarily glued everything up and checked that it was sitting square so I could drill a pilot hole through everything for the cylinder and water jacket.

 

[bmac2]

Split it up and drilled out the holes, ¾” for the cylinder and 1 ¼” for the water jacket. Then I cut out the opening for the body of the core on the bandsaw. The cut where I entered the block I filled with a small strip of wood veneer. Cleaned the residual newspaper off everything with the belt sander and glued it back together.

 

[bmac2]

Once the glue was dry I split the mold and gave it a quick cleanup. I think that once I had a plan actually roughing out the pattern didn’t take long at all. What takes time was coming up with the plan . . . and watching the glue to dry.
Looking at it really makes me want to melt something :noidea: but it’s nowhere near ready for that yet.

 

[bmac2]

Before going any further, I would suggest you read up on this site. There are corrections for dimensions for faults in the engine that you might already be incorporating without knowing it.

Go to this page

http://modelenginenews.org/index.html

John

AAaarg! So close!
Blogwitch I should have read that article (more carefully) before I started the core.
I remembered seeing it a while back and thought I was using the corrected measurements, but I missed this one.
Oops.:shrug:

 

[bmac2]

It’s Just as well. I don’t think I had allowed enough for the surfaces that have to be machined. As an exercise in getting the basic form right I think I’ll give myself a passing grade but as far as workable pattern goes it’s a fail.

 

[bmac2]

So it was back to the CAD last week to tweak it a bit and start over. Good thing I have full scrap bin of woods and an understanding wife.

Correcting the pattern turned out to be as simple as scaling the 2D drawing up a bit and changing the thickness of some of the pieces. I didn’t take any pictures while making it. If you want just look at the pictures of the last one and imagine it’s a little bigger.
I did take a riveting video of splitting the pattern with a putty knife with my hand in the way. Thm:

[ame]https://www.youtube.com/watch?v=eKf3Pk56dDs[/ame]

 

[bmac2]

I’m feeling good about this one so I gave it some paint. The holes for the locater pins are drilled before splitting the pattern.

 

[bmac2]

I messed up and painted the loose piece before I sanded off the edges so I’ll have to get something on it to protect it. I still have to add the water inlet and the nub for the oil cap but I want to make sure it will pull from the sand before I move on.

 

[Blogwitch]

Don't worry about it B, we all make mistakes.

What would the world be like if everything turned out perfect all the time?

But just to put a few things right about that build I pointed you towards.

I had followed it from the very first words, and nodded my head every time a mistake in the castings came to light, I had been through the same routine a few years before when I used the Woking Precision casting set.

Luckily, after a lot of bodging workarounds (even to the point of getting some metal added by welding to certain areas), I managed to get mine built and running, whereas the two that they built never did. I think it was given up on because it was such a bad job. So much for Hemingway remaking the patterns and selling good quality castings.

As far as I am concerned, they lie like a cheap Chinese watch.

And I don't think it is just Hemingway either. From the feedback I have had from various people, it is suspected that Stuart Turner are using castings as patterns, and so there are lots of undersized casting sets out there that really are difficult to make unless you are a very experienced castings modeller, and you will get no help from ST when the problem is raised with them.

Keep up the good work

John

 

[fourstroke]

Thats turned into a really nice pattern
It will feel really good when you break your first mould and see the casting emerge
Dougie

 

[Charles Lamont]

Luckily, after a lot of bodging workarounds (even to the point of getting some metal added by welding to certain areas), I managed to get mine built and running, whereas the two that they built never did. I think it was given up on because it was such a bad job. So much for Hemingway remaking the patterns and selling good quality castings.

As far as I am concerned, they lie like a cheap Chinese watch.

And I don't think it is just Hemingway either. From the feedback I have had from various people, it is suspected that Stuart Turner are using castings as patterns, and so there are lots of undersized casting sets out there that really are difficult to make unless you are a very experienced castings modeller, and you will get no help from ST when the problem is raised with them.

John

I hope you are prepared to defend all this libelous speculation in court?

The reason why Ron Chernich never completed the write-up on the Whippets was his failing health.

 

[barnesrickw]

I'm not sure expressing an opinion on a private forum constitutes a libelous situation. And if so there are many, many people, including myself who are about to end up in court for posts about Harbor Freight and the like.

 

[Blogwitch]

I hope you are prepared to defend all this libelous speculation in court?

The reason why Ron Chernich never completed the write-up on the Whippets was his failing health.

I wish people would replicate the whole post rather than just part of it, the whole context was lost, and yes, I would challenge Hemingway to come to the fore and try to explain why their castings were still no good when even Ron admitted they still had major problems, exactly the same ones I came across when I built my engine from original Woking castings.
I would challenge anyone to attempt to make this engine from Heminway plans and castings, making the parts as drawn, using no intermediate bodges and trying to assemble it at the very end. It is guaranteed 100% that it wouldn't even fit together never mind run.


John

 

[Charles Lamont]

I'm not sure expressing an opinion on a private forum constitutes a libelous situation.

I think there is a difference between reporting poor service or quality and calling someone a liar, which is what Blogwitch did.

Drawing errors are ETW's, or the Model Engineer tracer's, probably stemming from trying to maintain publishing deadlines, and remembering these were mid-20'th century drawings - no CAD, no calculator, even. Hemingway had corrected the errors they knew about.

Where does Hemingway claim to have remade the patterns?

Tackling a casting kit requires care, checking things out and thinking them through - which is what makes it an interesting job. Expecting perfection from small size, small batch, sand castings is asking too much, and Ron Chernich says as much. I am (slowly) building a Hemingway Seagull, and some of the castings are not easy to get a good part out of, but I have not found it impossible.

Any supplier should be happy to replace a faulty casting. Has Blogwitch had any dealings with Stuart Turner since they were taken over by Bridport Foundry? They told me at an exhibition that they had to throw out much of the stock of castings they acquired from the run-down Guernsey business.

 

[barnesrickw]

There have been cases where libel against individuals have gone to court for damages. I have yet to find anything relating to a business.

 

[bmac2]

HAPPY CANADA DAY/ DOMINION DAY!

What better way to celebrate Canada Day than playing in the sand. I helped my wife this morning doing pink work so I’ve earned enough shop credits to go hide in the garage for a while. Thm:
This thing has to pull from the sand or this is a total waste of time . . . . fun, and a least for me educational, but a waste of time.

 

[bmac2]

My sand is still not quite where I want it but it’s what I have. Had to spray it down a bit as it has dried out since I used it last and rammed up the pattern.