From one cylinder to two...!?

[Drei]

Hi guys,

I was wondering if from a one cylinder engine plans, a two cylinder can be built from the same plans. Therefor using the same dimensions and design layout to manufacture the two cylinder.
I am talking on the on the engine designs that my earlier built engine which is the Lynx NE15 the one illustrated in the display picture. I tough by using some ideas seen from other dismantled engine, I can first design it on the CAD program using all the possible dimensions from the original plans and then machine it and hopefully work.
The biggest concern is that in a two cylinder in line engine, are the pistons timing 180 degrees apart? This means that the offset found in the crankshaft webs for the pistons stroke are 180 degrees apart ???This would be more easier in building the crankshaft and in calculating any timing because if so I dint know how!
Can all this be done ??? and is the crankshaft timing 180 degrees ???

Thanks Drei

 

[hudmut]

Well i best say some thing on this I'm doing what you are talking about right now.

Iv taken the NE15 added one more cylinder. All I'm really doing is making a longer crank case and moving the rear cylinder back 10mm and making the crank pin 10mm longer to pick up the extra rod. As for the cam timing just time it 180 out from the other side.

But when making a flat twin like i am just think about how you want you heads to be. because if you make 2 the same you will end up with ports all over the place make a mirror of each other and things will fall in to place.

I hope this helps iv got most of the engine in CAD on because of me cheating and using my cnc mill for as much as i can just to see if i can but the only real that has really hat to change is the crank case, crank pin, one head and cam shat as well as bearing. so you could do most of it with out having to do much CAD work at all

And one more thing im going to do is step the crank up from 8mm to 10mm as with the engien now being a 30cc it going to be under more load even more so with a 22" prop trying to pull the front of the engine out one more reson why iv all sod added a few more bolts all round

 

[jpeter]

Two inline cylinders? There's a couple of ways of building the crank. The old Trumph motorcycles brought the pistons up together and fired them alternately. That engine had a really nice sound. Later Honda's arranged the crank so the pistons came up alternately. I found the sound of that engine not nearly as pleasing. Anyway, its something you ought to look into before you start. Its been a lot of years since I learned that. I hope I have it right. Should be easy to research.

 

[mu38&Bg#]

Right, if both pistons move in the same direction, they can fire either at the same time every 720° or alternately every 360°. Balance is better when they move in opposite directions, but the second cylinder fires either 180° or 540° after the first, either way 180° apart.

A flat twin with two throws on the crank will fire every 360°.

 

[jpeter]

A flat twin with 2 throws is commonly known as a boxer engine, or does a boxer need to be more than 2 cylinders?

 

[Drei]

"Boxer more than two cylinders" well exactly Idont know !!

Continuing on what I want to add to my Lynx model, is that I want to remove the cam from the over head position to place it in the cranckcase. Therefore machining some roccekr arms and pushrods will be neccessary but i think thgis wouldnt be a problem. The reason in doing so is that in the few runs that i gave the engine, in totlat i had to buy nine belts.
After some time the belt starts to wear and starnd from the inside begin to snap therfor the belt doesnt remain straight and starts to slip when finaly it snaps.
By building the pushrods etc. i think it would be more reliable but on the other hand more mechanicla poer would be lost. but in my case im not looking for perfarmance i only want to save money and dont buy more belts ;D. Also this would give the engine a new look which for me i think it will look great.

 

[stevehuckss396]

I was wondering if from a one cylinder engine plans, a two cylinder can be built from the same plans. Therefor using the same dimensions and design layout to manufacture the two cylinder.

The short answer is yes.

The long answer is yes and no. You could do it but with all the design changes you propose, making some sort of drawings could save you alot of time and effort by avoiding mistakes. If I were in your shoes, I would draw the entire engine before making the first part. First decide on the crankshaft arrangment and then you can design the cam and snow ball from there.

 

[jpeter]

The conversion would involve so many changes and, at least in pictures, the current one is so cute I'd consider starting over. You'd end up with two pretty nice engines. Sounds like all you could salvage is a cylinder and piston. Make some plans to get the tops of the cylinders aligned with each other or the head gaskets won't seal properly. Multi cylinder engines are fussy that way. The belt story is interesting. I use a 3 mm wide belt on a model helicopter tail drive and have very little belt trouble. Strange about yours.

Hey, if you get a chance check out my v8.
[ame]http://www.youtube.com/watch?v=B9zt3SF_Flc[/ame]