Another Water-Cooled Twin

[johnlaudano]

This is my current twin under construction. The bore is 1.38 and the stroke is 1.42. More soon.

 

[kuhncw]

Nice work, John. I'm looking forward to seeing more of your new design.

The crankcase and cam housing appear to be a weldment. Which welding process did you use?

Chuck

 

[johnlaudano]

Thanks Chuck. Yes, it is a weldment. I mig welded it and ground the welds with a ball burr. I liked the texture it made so I applied the technique to the rest of the surfaces. Paint should make it look somewhat like a casting.

 

[johnlaudano]

This is the in-line twin 69cc finished. The plan is to put it in a 70" boat if it runs well enough.
John

 

[kuhncw]

Very well done, John. That is quite a plumbing setup. Is the top pump an oil pump? Is the cam housing open to the crankcase?

Do you have a photo of just the welded up crankcase and cam housing you could post?

Do the sections of tubing between the two bands/rings form the water jackets? How are the cylinders attached to the crankcase?

Lots of questions, I know, but you've got quite an interesting design there.

I'm looking forward to hearing it run in a video.

Regards,

Chuck

 

[johnlaudano]

Thanks Chuck. Yes one pump is for oil and the other for coolant. The oil is directed to the center bearing of the camshaft.
The cam housing is open. There is a photo below.
The cylinders are from solid cast iron and the four screws on top of the engine go all the way to the crankcase; I would not do that again as its too difficult to make long straight holes.
Coolant flows around an annular groove near the bottom of the cylinders and then flows up thru holes in the cylinder. I'll send a PDF of the drawing.
I'll send more photos soon; I keep getting a message about a server problem while I'm trying to upload. John

 

[johnlaudano]

PDF's of Partial drawings. John

 

[johnlaudano]

more photos...

 

[kuhncw]

John,

What was the material you used for the crankcase and cam housing? It looks like smooth bore tubing. Those are babbitt rod bearings? Interesting rods. They look just like little castings or forgings.

Is your lube system a dry sump system.

Thank you for posting the photos and drawings. As I look through them, I'm sure I'll have more questions.

Regards,

Chuck

 

[johnlaudano]

Chuck,
The tube was smooth bore tube I had left over from a different project. I don't recall the alloy but it machined well.
The oil is from the crankcase with no other oil tank; the oil is about 5/8 deep in the crankcase. The crank is a 180 degree design and I anticipate there will be little pumping action. I'll probably need to reduce the volume of oil but i need to start somewhere.
The pumped oil set-up is probably unnecessary but creativity sometimes takes over. Also, if you look closely, you can see the cam center bearing inside the crankcase is bonded in-place with metal-filled epoxy. This was done to assure alignment. It was bonded in-place with the cam and cam end bearings installed so that alignment was assured; my machinery can't hold close enough tolerances to machine everything as true as it needs to be.
Yes the big-end bearing is poured Babbitt and the rods are actually rods from a homelite saw.

 

[kuhncw]

John,

Thanks again for the photos and comments. This is a very interesting concept for engine construction.

Please keep us tuned in as you get to running it.

Chuck

 

[johnlaudano]

Finally I have it running. had to convert to an airplane carb on gasoline and reduce the intake valve lift.. Needs some fine tuning. Any thoughts on why the fuel mixture is hyper sensitive? one click either side of running stalls it.
More video soon.





John

 

[Rustkolector]

John,
It could be the carb. My guess is too large. What is the carb throat dia? Have you tried this carb on propane? I use RC carbs with a demand regulator on most of my engines. I use a 3 mm throat size carb on a 4 cylinder 1"b x 1.125"s. I don't run it that fast, but it will go faster if needed. Using RC carbs you just have to turn the needle out a few more turns and be sure no air leaks past the needle threads.

What is your required top RPM and your valve timing?

Very nice and unique engine design. Hope this one makes into your boat.
Jeff

 

[kuhncw]

John,

Nice work. Your new twin runs well and has a good strong sound. It runs well over the speed range. My favorite thing about this engine is your welded crankcase construction.

With the 1.38 dia bore, you should have plenty of power for you boat.

Please keep us up to date in this project.

Chuck

 

[kuhncw]

John, would you please tell us about the ignition system. I see two coils.

Chuck

 

[johnlaudano]

Thanks everyone. The carb bore is at least 7mm so a smaller one may be in order. I haven't checked rpm's yet; that will be on the next run. There are minor leaks to fix first.
The ignition is two TIM 6's from J. Howell with a coil for each cylinder. I realize its an expensive way to do it but its less complex than incorporating a distributor.
Attached is the intended valve timing chart. The theoretical lift was going to be .165. I simply increased the valve lash to reduce the lift; that changed the valve timing to something I haven't measured; I was just happy it ran. After some more test runs the boat project can continue.

 

[Noel Gordon]

John, Please take a well deserved pat-on-the-back as you have made a very nice engine and I so hope that it gives you hours of fun and smiles ..A very nice job..

 

[Rustkolector]

John,
With a twin cylinder engine you can use a single coil waste fire ignition for either 180 or 360 degree crankshaft design engines. Use a Hall sensor for timing and just add one more magnet for 180 degree crankshafts. S/S offers a very compact CDI waste fire ignition using 4 AA batteries. I have used it with both crankshaft designs with excellent results.

Your valve timing is more suited for a rather high speed engine and not so smooth an idle. Increasing the intake valve lash reduced the intake valve duration lengthening the compression stroke which could be the reason it now starts and runs so nice at low speeds. Intake valve closing is the most important valve event and has a lot to do with the engine's speed range capability. Use an intake closing at 10-15 degrees after BDC for a slow to medium speed engine for a good idle. Later closing will give higher speeds, but likely a less than smooth idle. It would be very interesting to know what the intake valve timing is now and if the top RPM still suits your hull requirements. If so, it sounds like you are there! Time to try the propane again.
Jeff

 

[johnlaudano]

Thanks Jeff. I follow the "waste" spark idea but the TIM 6 won't fire two plugs simultaneously. will the s/s fire two plugs at the same time?

 

[Rustkolector]

John,
Yes, the S/S wasted spark version of the S/S CDI ignition will reliably fire both plugs simultaneously. See two links below: the first is a 180 crank engine and the second is a 360 crankshaft. Both are using the smaller 10-40 thread Rimfire spark plugs. Someone else on this site may have had experience with Roy's CDI with larger plugs. I have one S/S CDI on a single cylinder engine that used to jump spark 3/8" to ground when the 1/4 - 32 spark plug fouled with oil.
Jeff