Halfa, a DOHC inline Twin

[vtsteam]

Tick, Tick. Tick... 

(but I liked clickety clack, too)

[Admiral_dk]

Sound much healthier now, you have removed the slack 

A very good omen for the finished Engine and it's running qualities (when you get there) 

Per

[Art K]

Looks good Ron!
Art

[RReid]

Steve, Per, and Art - Thank you!

Won't be much progress for the next couple of weeks as we are keeping watch over the Oregon grandkids while eldest Son and daughter-in-law go off for an anniversary trip.

[RReid]

Even though I've been away from the shop for a bit, I have been able to come up with a carburetor concept that I hope will work with this engine. It is basically the "Howell 2-Jet Throttle", plans for which are available at nominal cost from the Jerry Howell website.

I have redrawn it in Alibre for 3 reasons:
1) To better understand the design
2) To reduce the size of the throat & throttle vane slightly, from 0.25” to 0.1875”
3) To make cosmetic changes in an attempt to make it look just a bit similar to a 2-throat carb in the manner of a Weber DCOE, including a “dummy” pair of intake trumpets (they function, but are siamesed to a single throat through the carb).



I've also been re-drawing the Britnell Tube Bender, simply for reason #1 above. It will be useful in fabricating the exhaust header, and is something I've been making do without for long enough!

[Admiral_dk]

2) To reduce the size of the throat & throttle vane slightly, from 0.25” to .01875”

I'm not sure the I would call a 3/40 reduction a minor one 

But I like you attempt to make it look like a bigger brother 

Per

[RReid]

I'm not sure the I would call a 3/40 reduction a minor one 

I don't know how that decimal point got moved...must have been one of the grandkids.

(Thanks Per, I've fixed it)

[RReid]

After something of a hiatus, I've been able to get back to this engine. I've used my newly made and commissioned Britnell Tube Bender to make up a set of exhaust headers. Tomorrow I'll finish cleaning it up and give it a coat of barbecue paint. Then start working on the intake side.

[Kim]

That's some nice fabrication, Ron! 

So, beyond using the Britnell tube bender, how'd you go about cutting the curved tube so it would fit snug against the other one? That's a pretty neat trick!

You're soldering looks really nice too.

Kim

[Roger B]

That's neatly done    I know how difficult it is 

[Charles Lamont]

Kim, for what it is worth, here is how I have done it:

http://www.charleslamont.me.uk/Seagull/fabrications.html#pipe_joints

[RReid]

Thank you, Kim, Roger, and Charles.

, how'd you go about cutting the curved tube so it would fit snug against the other one?

It was more of a free-bashing method than Charles' more controlled approach, that's for sure! I was thinking and working at the same time, so I guess no bandwidth was left to pick up a camera!

Basically I eye-balled the spacing against a steel rule and cut a notch in the main tube slightly smaller than what I thought I needed, using a combination of saw, Dremel, and files. You can fairly well see the outline of that notch in the top pic. The second tube was cut to fit into that notch, starting out with it oversize. Slicin it lengthwise was done by clamping it in the vise just below the mid-line and using the top of the vise jaws to guide a fine tooth hacksaw blade.  Bad for the set of the blade, but doesn't hurt the jaws much! Then alternating between both parts with files mostly until the fit is good.

Compared to a locomotive boiler, that bit of soldering is trivial! A pair of parallel clamps held things tightly together, and 1/32" diameter solder was cut and bent to fit all along the seam line and to hold itself in place.

[Kim]

That's pretty tricky work! It came out very good, Ron!  Looks beautiful!

Charles, that's a great way to do it too. Thanks for sharing that.

Kim

[RReid]

Thanks Kim!
Turns out something came up and our grandkid minding services are required again, so I'm out of the shop again for a bit. Here's a parting shot of the header all painted up and in place. Not so sure those bright hex heads and washers will make the final cut.

[RReid]

Interesting past few weeks. We spent almost 3 weeks in March staying with the Portland grandkids while Mom and Dad went to Europe for a well deserved 15th wedding anniversary trip. This had been planned for quite awhile,and we had a good time with the kiddos. About a week and a half after we got back home, Monica's mother passed away, quietly and not unexpectedly, but that meant that we would be needed again to watch the kids so they could go to SoCal for the funeral. We got the call on Easter Sunday, and said, OK, we'll be there tomorrow. It's a minimum 10 hour drive from here to there. Unfortunately that morning there was a “police involved shooting” alongside the interstate in Salem, OR, about 50 miles south of where we needed to get to, which closed the north bound lanes for several hours. By the time we got there one lane was open, but it still took us at least an hour to crawl three or four miles. Which meant we got to the Portland area as the commute traffic was getting into swing. We finally got there after a 12 hour drive.

We expected Dan and Monica to fly home on Saturday. Except on Thursday Dan tested positive for Covid, so would have to isolate and couldn't fly home until at least the following Wednesday. OK, we can stay longer. So we finally left for home on Thursday. This time we made it a two day trip, staying at a nice and reasonably priced place we know at the base of Mt. Shasta that serves a complimentary glass of wine in the evening and is right next door to a quite good Mexican restaurant. Whew!

So now I have been able to make a little progress on the carburetor for this engine. I've started on the carb body:




But I found I need to order some very small drills, so I also switched over and started work on the throttle shaft.


The carb body also needs a 0.117” diameter reamed hole for the spray bar, so I went ahead a made a D-bit reamer for that out of a bit of drill rod.