V6 Engine Timing

[Novian]

Hello,
I've been roaming this site for a while now; looking at people's amazing engines. I've spent alot of time going over kcmillin's Tiny Inline 4 Cylinder IC Engine, keith5700's 1/4 scale V8 Engine, and stevehuckss396's Small V8 Engine.

I'm thinking of making my own IC engine. Since I wanted to be different, having not seen many 90 degree V6's on this site, I chose the V6.

I have most of the 3D Model of the engine complete.

I believe the only missing parts are: Timing Gears (more on that later), carburetor, Proper spark plug timings.

Check out these photos:

Over Head Cam Model

Over Head Cam Model 2

Over Head Valve Model

Over Head Valve Model View 2

Those white pipes are the exhaust headers; just a quick drawing on that part.


The engine dimensions are as such:

Case: 3 53/64"Width X 3 53/64"Hieght X 6"Length(excluding the 1/2" thick end caps)

I feel that the way the case is shaped provides a built in oil pan.

Pistons: Length: 3/4"
Diameter: 1"
Stroke(travel in the cylinder): 1 11/32" difference

Crankshaft: Largest Diameter (the used rod would be 1 5/8" Diamter)

Piston Arms: 2 1/2" total length

I am wondering if this engine has any potential in running, with some changes ofcourse.

Also, i am looking for advice on how the timing works for this type of engine. Answers such as the ratio between the gear on the crankshaft to the cam rods would be extremely helpful. I will also be greatful for some web links to pages containing such information that i can learn from.

As you can see in the above photos, i have two versions of the possible valve systems. One is with DOHC (Double Over Head Cam) and the other OHV (Over Head Valves). I'm not sure which version to choose from, but the OHV version seems like it would be easier to make once i find out the gear ratios.

I am very new to machining, i dont have a lathe or milling machine yet (planning on getting the lathe this weekend). You might have seen the Elbow engine that i made a while back. I'll redo the cylinder blocks and complete it once i get the lathe before i start working on this engine. I know that this is a HUGE step forwards from a simple looking 12 piece elbow engine, but once i get my mind on a project, i dont stop thinking about it until something new comes along.

Thanks,

Ian




Here are some more photos:

Exploded 1

Exploded 2

Piston

 

[Admiral_dk]

Unless you plan to make some very different cams, one thing is sure : The ratio between crank and camshafts is always 2:1 on a four stroke engine. This has nothing to do with number of cylinders - only exception are radials, but their cams are different in most cases.

 

[Lakc]

This looks like an interesting project.
Your best source is any old factory automobile service manuals. The Chrysler ones all include a theory of operation section, and full cam timing specs, as well as numerous other specs that you can compare your design too.

 

[Swede]

That is some really nice modeling work.

Wouldn't it be better for the cams and rockers to be solid as opposed to split like they are? I'm thinking the wear would be accelerated with the split cams. There's a surprising amount of force on even small engines like this.

How will the cylinders be cooled? Water cooled?

I can't think of any reason it wouldn't run. Obviously the critical areas are induction, compression and compression ratio, cooling, valves and everything associated with them. One of the harder things to do with a small engine are making effective valves that seal, and good rings for the piston. Also, the cylinder bore (finish, accuracy) is a leap beyond a steam engine, and lapping or honing (I prefer lapping) will be a skill that must be mastered.

 

[Novian]

That is some really nice modeling work.

Wouldn't it be better for the cams and rockers to be solid as opposed to split like they are? I'm thinking the wear would be accelerated with the split cams. There's a surprising amount of force on even small engines like this.

Thanks, i feel that I've gain some skill in modeling in sketchup. i even like it more than the student version of all the autodesk cads that i have (inventor, mechanical, architectural). I feel that Sketchup is the perfect spot in between 2D and 3D software.

Yes, i realised that when taking the screen shots. it will be easier to not have those two prongs, and to just have the 1 big one.

How will the cylinders be cooled? Water cooled?

I can't think of any reason it wouldn't run. Obviously the critical areas are induction, compression and compression ratio, cooling, valves and everything associated with them. One of the harder things to do with a small engine are making effective valves that seal, and good rings for the piston. Also, the cylinder bore (finish, accuracy) is a leap beyond a steam engine, and lapping or honing (I prefer lapping) will be a skill that must be mastered.

Right now, you can see the fins on the top of the head, where the valves are located. I'm guessing now that they wont be enough? I've seen on a 90 2 stroke that it had fins all along the circumference of the cylinder, so i could just cut more fins on the sides of the cylinder blocks.

Don't i have to worry about how much fuel gets into the cylinders when the valves are open? i don't know how precise engines need to be in that factor, but how do you get the valves to stay open long enough for enough fuel to get in, or stay open short enough so that not too much fuel gets in that the whole thing blows up? Please enlighten me on those factors.

 

[Novian]

I started drawing up a V8 version and decided on improving the case for the crank shaft. i was able to make it more compact, so that there isn't as much space where the crankshaft sits. I used the same case to improve the V6. it creates changes on the engine's stroke travel, but that should be better since it will make it more of a square engine, instead of the very over square engine that it once was. I will have to scale down some of the parts, including the pistons, but hopefully it will be worth it.

Here's a comparison of the original case, and the new case.

If you're wondering, the reason i changed the crankshaft that caused all these other changes is to make making the crankshaft more presice. The old crankshaft had values such as ~57/64" (~ is displayed on Sketchup, and it means that the value is close to the dimension. It does not provide something like 0.890625". If it did, I'd be able to use a caliper to machine those values).