Making a 10cc Whippet pattern

[bmac2]

To get it to match the radius of the block and set the downward angle I dug around in my “sanding stuff” drawer and came up with a 1 ½” drum sander that was close enough in diameter to the block pattern and sanded it in. All that was left was to glue it on and added a fillet to smooth everything out.

 

[bmac2]

The Filler plug was added basically the same way and once everything was set and dry I rammed it up in the sand to make sure it would still pull then gave it a couple coats of paint.

 

[bmac2]

You just have to love summer in Alberta. It’s 27c with a nice cool breeze and I have the day off with nothing to do that can’t wait. With a day like this I thought I’d do some more pattern work.
For the cylinder head and cover I sliced up my CAD drawing and printed the parts in 2D scaling it up 2%. Glued them to the wood and cut out the inside and outside profiles on the scroll saw leaving enough for sanding.

 

[bmac2]

Then I cleaned the paper off and glued them up. With the draft angle set on the belt sander I then took it down to the final shape. For the cover I drilled the holes for the dowels and glued them in before cutting out the profile. With a bit of filler and some sanding they were almost done. I’d left the dowels in the cylinder cover long thinking I’d just sand them down to what I wanted and it looks like the maple didn’t appreciate it.

 

[bmac2]

Added the boss for the sparkplug and after a bit more fiddling I gave them a quick coat of the scratch filler primer Dougie (fourstroke) introduced me to. I like this stuff a lot. Fills nicely, fast drying and sands easy.

 

[bmac2]

All that was left was to see if it would pull from the sand. With the sparkplug boss I have to dig down along that face to create a parting line along its centre. The tape is to cover a small hole in the pattern that a screw goes into when the part is pulled. The pattern came out smoothly and I think I might finally be getting my green strength about right.
If you look closely in the last picture you can just make out the impression left in the sand from the masking tape and a small dimple from the screw hole.

 

[bmac2]

Just to finish it up I gave them a coat of the blue and set them aside with the block. There’s got to be nothing better than a beautiful day with nothing to do but work on a hobby I enjoy.
Oh and some quick drying paints and fillers. Thm:

 

[Swifty]

I have no current intention of ever casting anything at home, but I'm still enjoying your thread. I'm always interested in how things are done.

Paul.

 

[bmac2]

Woohoo it’s raining. My wife got a nomination for a local “Yards In Bloom” award so if I have a free minute I think I’m supposed to be out grooming a plant of dusting a tree or something, but it raining. woohoo1
This means I got to work the Main Bearing. I’ve decided not to cast the detail on the inside (left side) of the casting and just make sure I have enough meat in the casting to machine it.

 

[bmac2]

I started out by cutting a disk from ½” plywood with my ridiculously out of balance circle cutter then used the newspaper and glue trick to attach it to the work plate on my little wood lathe using the tailstock centre to line things up. Used the hole in the disk to mount a length of 3/4” dowel and took this down to just over 5/8” diameter (small end) with a slight taper going back to the disk and a 1” long stub on the end so it can be chucked in the lathe.

 

[bmac2]

I was tempted to leave off the three little wings that go around the bearing mount thinking that it would be ok and I could just redo the pattern making it beefier if needed. Part of this was that I just didn’t feel like getting out the thickness planer (its heavy) to make up some 1/8” stock.
Then I remembered all the stir sticks they gave us when we picked up the stain for the house (post #23). These things are a nice straight grained wood and close enough to 1/8” for what I want.
Cut three pieces from the stir stick and glued them tougher with newspaper then just eyeballed the pattern for the wings and shaped them on the belt sander. With that done I split them apart and sanded some draft angle into them.

 

[bmac2]

I don’t have a tailstock chuck for the wood lathe (I know, I should make one) so I took it into the house to drill a ½” hole in the back for a second 1” stub and add a little thickness. This has got to be the first time I have ever use a Forstner bit I the Myford.

The bonus I discovered after doing this was that I’d put the wood into a three jaw chuck that made 3 evenly space marks for the little wings. Who would have thought that clamping something too tight in the chuck could be beneficial. Thm:

 

[bmac2]

I was a little concerned because the pattern finished up about 2” long with very little draft. Nothing to be done but ram it up. As it turns out my sand held just like in the books so the bearing pattern has earned some blue. Adding that extra clay has really made a world of difference. ;D

 

[barnesrickw]

You are a good man bmac. If you had been nominated for hobby machinist of the year, would she help you clean your shop?

 

[bmac2]

You are a good man bmac. If you had been nominated for hobby machinist of the year, would she help you clean your shop?

Aaaaaa. NO!

Actually she did that once. She’d been laid off and after we talked about it decided she should just take the summer off. One day I’d called her from work and she told me she was “tidying up my work shop for me”. When I got home after what felt like the longest afternoon in my life I found she’d done a pretty good job of it. I was amazed that she’d dumped out my catch-all bins and managed to sort all the miscellaneous nuts, bolts, screws, oddball electronic parts and printer guts into bins without really knowing what she was looking at. I guess you just can’t underestimate the tenacity of an accountant with a German heritage.

I don’t mind the extra bit of yardwork. After all we will probably have snow on the ground by late October and that leaves me with not much to do until April. woohoo1

 

[barnesrickw]

She's a keeper.

 

[bmac2]

I have been thinking about this timing case for a while now it’s a relatively small part but from the standpoint of a casting pattern it’s a complicated little piece of kit.
I had 3 options.

- Make it solid and just machine out the back.
- Make basically the same thing and make a core for the inside.
- Pattern it after the finished part with a hollow back.

 

[bmac2]

I think the option with a core has the potential for the greatest detail but it seems a bit over complicated for a part that’s not much bigger than my thumb so In the end I decided to try to do it with the hollow back. Before I could cut it out I wanted to get the bosses in. I’d run out of dowel but they are under an inch long so I dug out my set of plug cutters. One advantage to these is that they cut a tapered plug with the small end at rated diameter so the draft is built in.

 

[bmac2]

To make dowels you just mount the wood vertically so you are cutting along the grain and plunge the cutter in. Then just mark the board 1” inch in from the end and cut it off on the table saw. I liked to use these with furniture because you can use a cut off from the same board to match the grain and colour making the plugs almost invisible.

 

[bmac2]

With the bosses rammed in and the scroll saw set for the draft angle I cut out the inner and outer profiles. Made the top from my new found stock of 1/8” paint stir sticks and glued it in place. With the bosses I couldn’t use the belt sander so I had to dig around and find my small detail hand sanders.