Author Topic: A new look at Opposed Twin i.c. Engine  (Read 3327 times)

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #15 on: September 23, 2021, 09:56:04 PM »
All four ball bearings have been installed, two on the camshaft and two on the crankshaft. I still have some spacers to make and will put up a picture after they are installed.

Offline mikehinz

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Re: A new look at Opposed Twin i.c. Engine
« Reply #16 on: September 23, 2021, 10:25:07 PM »
Brian, I'm watching this closely as some day, when I get confident enough, I'd like to attempt some version of a twin.  I can see clearly that there are various tricky bits!

Thanks for all the great information you give out here on the forum!

I'm watching closely.

Mike. 
MIke
Wichita, KS, USA

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #17 on: September 24, 2021, 04:20:24 PM »
So, here's a picture of the crankcase with all ball bearings installed. There isn't that much that you really can see. I had to open up a few counterbores and make some bearing spacers, but it's all done without having had to change the overall shape and dimensions of anything. The camshaft bearings set about 0.020" proud of the top surface, but that isn't a problem, as there is a magnetically attached plate over that top surface when everything is put back together. I am so happy that I didn't have to make a new crankshaft o camshaft.


Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #18 on: September 24, 2021, 05:09:44 PM »
I have never been happy with the base I made for this engine. I am going to build a new, much shorter base because I think the proportions are better.

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #19 on: September 25, 2021, 10:39:52 PM »
Today I shortened the plate directly below the crankcase, and machined two new "feet" that are much shorter than the original ones. I stuck that evil looking flywheel/fan on just to make a good picture.

Offline Craig DeShong

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Re: A new look at Opposed Twin i.c. Engine
« Reply #20 on: September 26, 2021, 12:28:07 AM »
Brian

Youre making good progress on this twin.  Ive had a fascination for twins, ever since I nearly traded my Honda for one of those classic BMW motorcycles way back when, that had the twin opposed cylinders.  Loved those bikes, but had I stayed with riding motorcycles, today Id probably just be that cousin in some distant relations photo album.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #21 on: September 26, 2021, 01:56:44 AM »
Hi Craig--- I've got a whole room full of engines setting around, but I've been thinking of redoing the twin for a long time now. I was very lucky that I didn't have to make a new crank or cam. I have two sets of cylinder heads for it. The first set of original heads had the sparkplugs right at the very bottom, and if you flooded it on start up you had to take the plugs out and dry them off and blow out the cylinders. The second set of heads were a redesign that raised the sparkplugs to the center, but I never did get it to run right because of undue wear on the crankshaft bushings and the fact that my short sparkplugs set way down below the rocker arm towers. I think the sparkplugs were shorting out to the rockers, but it was in a very difficult spot to see. I don't have to really make anything more now, just a bunch of rearranging things. Your new project looks very exciting, and I have a look every time you post.---Brian

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #22 on: September 26, 2021, 06:24:12 PM »
Today I reworked the flywheel/fan guard to fit the shorter engine base. Also took the opportunity to J.B. Weld shut a bunch of holes I had drilled in the guard to mount a governor. The governor kinda sorta worked, but I could never get the engine to run consistently long enough to get the governor tuned properly. I may still try a governor to control this engine, but if so it will be mounted on a separate base and connected with an o-ring drive belt.

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #23 on: September 27, 2021, 10:11:16 PM »
Well, that's a day out of my life, but it's been a good day. There was no way I could rework the coil mounting and switch bracket to make them work with the new engine frame, so I built new ones---and modified the guard for the wicked flywheel/fan to fit the much shorter engine base. Everything looks a bit rough right now, but I haven't done my cosmetic magic yet. Tomorrow I will tidy things up a bit, and see what's involved with mounting the gas tank and cylinders---They should just be direct bolt ons.



Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #24 on: September 28, 2021, 06:09:07 PM »
Today seen the cylinders cleaned up and reinstalled, along with the pistons and connecting rods. I could have used one of Chris's elves to get down into the crankcase and tighten the rod bolts. I had forgotten just how inaccessible they were when the bottom plate was installed on the crankcase. I had to take everything apart to get at the rod bolts to tighten them. Before I go any farther now, I have to time my valves before my gear cover goes back in place.


Offline crueby

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Re: A new look at Opposed Twin i.c. Engine
« Reply #25 on: September 28, 2021, 06:29:07 PM »
So THAT'S where that little guy went, I was worried he got shut in one of the toolbox drawers.   :Lol:




Engine is looking good, getting closer to seeing it run again.   :popcorn: :popcorn: :popcorn:

Offline Roger B

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Re: A new look at Opposed Twin i.c. Engine
« Reply #26 on: September 28, 2021, 08:05:26 PM »
A fine rebuild  :ThumbsUp:  :ThumbsUp: I'm following along  :wine1:
Best regards

Roger

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #27 on: September 29, 2021, 02:23:04 AM »
Hi Roger--Thanks for looking in and leaving a comment.---I just spent an hour reading thru all the posts made on the forum when I originally built this engine, and I discovered something. On the original build, that diamond mesh on the flywheel guard was between the flywheel and the engine. Now it's on the other side.  Ah well, I didn't plan on sticking my fingers in there anyways.

Offline Brian Rupnow

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Re: A new look at Opposed Twin i.c. Engine
« Reply #28 on: September 29, 2021, 11:43:42 PM »
So, here we are, all reassembled. Crankshaft and camshaft are both riding in sealed ball bearings. That lever at the very front of the engine has my ignition points mounted on it, so I can adjust the timing by lifting the lever up or down. The plate will rotate to the limits of the curved slot, letting me fine tune the timing while the engine is running. That knurled pulley and key setting in front of the engine  go on last, as it has part of my starter which I engage with my variable speed drill. I still have to remove the fan guard and give it a bit of cosmetic work and a new paint job. I might machine a swoopy looking air horn to fit on the intake side of the carburetor. Tomorrow I have some real, paying design work, so I probably won't post anymore progress for a couple of days.

Offline Admiral_dk

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Re: A new look at Opposed Twin i.c. Engine
« Reply #29 on: September 30, 2021, 11:29:36 AM »
So not far from the first pop in the revised version :ThumbsUp: