# 4 cylinder ohv engine plans



## gbritnell

After posting pictures and videos of my 4 cylinder ohv engine I got some requests for drawings. I have completed a set of drawings for this engine. There are 13 drawings to the set done in 8-1/2x11 format. If anyone is still interested please contact me offline at [email protected] for further information. I am including a couple of pictures so you can see the quality of the prints.
gbritnell


----------



## stevehuckss396

Why not upload them to the file section.


----------



## Stan

I expect the plans are for sale.


----------



## Noitoen

I wonder if someone can explain. Looking at the crankshaft of a 4 cylinder engine like this one, the same as the normal full size ones, why are there always 2 pistons TDC and the other 2 "BDC"? Wouldn't it be better to "space" them 90º of each other? In this way one could have a power stroke at 90º intervals probably making the engine run more smoothly. At least it's what I think. Maybe it's easier to build them the way they do.


----------



## Captain Jerry

The two cylinders that seem to be paired are really 360 degrees out of phase. One is TDC after compression and the other is TDC after exhaust. The other pair is BDC after power and the other is BDC after intake. You only get two power strokes per revolution in a 4 cyl, 4 stroke IC engine. The crankshaft on a 4 cyl, 2 stroke engine looks a lot different.

Jerry


----------



## Noitoen

Captain Jerry  said:
			
		

> The two cylinders that seem to be paired are really 360 degrees out of phase.



That I understand, but if they were 90º out of phase, then for example, the one at 12 o'clock would be entering the power stroke, the 3 o'clock one, 1/2 way through intake, the 6 o'clock entering the exhaust, and the one at 9 o'clock, 1/2 way through compression cycle. This way the firing would be at 90º intervals instead of 180º.

Helder


----------



## Captain Jerry

You still only get two power strokes per rev. The beat would be more like a polka than a foxtrot. 

Jerry


----------



## Noitoen

The way I see it there would be 4 power stokes per revolution, separated at 90º, unless I'm not looking right. Must make a drawing to confirm.

Helder


----------



## stevehuckss396

Noitoen  said:
			
		

> The way I see it there would be 4 power stokes per revolution, separated at 90º, unless I'm not looking right. Must make a drawing to confirm.
> 
> Helder



The thing you have to remember about 4 stroke engines is there is 720 degrees per timing cycle. So the ideal firing is 720/4 or 180 degrees per fire.


----------



## Kermit

Noitoen  said:
			
		

> That I understand, but if they were 90º out of phase, then for example, the one at 12 o'clock would be entering the power stroke, the 3 o'clock one, 1/2 way through intake, the 6 o'clock entering the exhaust, and the one at 9 o'clock, 1/2 way through compression cycle. This way the firing would be at 90º intervals instead of 180º.
> 
> Helder




What about Balance of those reciprocating masses at the end of the rods? The forces generated at top speed are alot more than their weight alone. Alot of the reasons for the way these things are done, is most likely balance related. Setting up one to run as you suggest might be possible but most likely something like vibration would probably make it not worth doing.


How's that for random keypressing?,
Kermit ;D


----------



## Noitoen

I wonder how the Audi's 5 cyl engine's crank looks like.


Helder


----------



## gilessim

you have to remember that it's a 4 stroke , ie; suck, squeeze, bang, blow! (induction ,compression ,ignition ,exhaust) and the firing sequence on a 4 cylinder is usually 1-3-4-2, and as Steve says you have a bang every half turn of the engine (as in for each "power stroke" the piston has to go up and down twice), if it were a 2 stroke it would be a different matter, but as for the stresses involved, the bangs are absorbed by the cylinders on their compression stroke, Audi's in-line 5 cylinder (they weren't the first to try it by the way!) was an attempt to balance and smooth things up a bit but it's more of a gimmick than anything else IMHO,anyway, just think that a single cylinder 4 stroke still has to go round twice to complete it's cycle!


----------



## gbritnell

Hi Stan, yes the drawings are for sale. Normally I would post things in the files section but I have almost 2 months work in these. I had to disassemble most of my engine, measure it, make sketches and then make a complete set of AutoCad drawings. The set includes a sheet on making the carb and also a step by step on making the spark plugs. As I mentioned if anyone is interested I have the set of drawings and a CD with pictures of the actual engine.
gbritnell


----------



## steamer

Hi George,

Forgive me if you have already posted this, but could you post A picture of your engine?

Dave


----------



## ksouers

Dave,
It was Engine of The Month in October. Here ya go.

http://www.homemodelenginemachinist.com/index.php?topic=3028.0


Kevin


----------



## steamer

Ahhhh...Now I remember! :-[ :
Thanks Kevin

Dave


----------



## ksouers

You're welcome, Dave.
Beautiful engine, isn't it? I'd love to build one but there ain't no way by skills are up to it. Yet ;D


----------



## steamer

Damn Sexy actually........its on "The List"

I figure I'll be about 119 by the time I finish building everything on the list. ;D

Dave


----------



## DICKEYBIRD

Beautiful drawings George! :bow: Being an amateur draftsman, I can really appreciate the time that went into them. You experts just make them look "right." I hope you sell a ton. ;D


----------



## meto

I purchased the 4 cylinder engine planes from George Britnell they are great plans nice cd shows pictures of engine . good job George Ken Reynolds


----------



## gbritnell

I have found 2 omissions on the plans for my 4 cylinder OHV engine. I am posting a picture of the additions for those who bought a set of drawings. I appologize for any inconvenience this might have caused. I don't have everyones mailing address that purchased these plans so if you contact me I will be more than happy to mail you out the new sheet. 
Thanks,
gbritnell


----------



## stevehuckss396

Got it G! Thanks for the update!!


----------



## gbritnell

Steve, I have your address so I will be sending you out a sheet with the new dimensions on it.
gbritnell


----------



## stevehuckss396

Good deal! Thanks


----------



## gbritnell

I got the copies printed up today so they'll go out in Monday's mail. I have 6 names and addresses so if anyone else reads this forum and bought a set of drawings at NAMES just let me know and I'll send you the drawings with the additions.
gbritnell


----------



## DickG

Noitoen said:


> I wonder if someone can explain. Looking at the crankshaft of a 4 cylinder engine like this one, the same as the normal full size ones, why are there always 2 pistons TDC and the other 2 "BDC"? Wouldn't it be better to "space" them 90º of each other? In this way one could have a power stroke at 90º intervals probably making the engine run more smoothly. At least it's what I think. Maybe it's easier to build them the way they do.


If they are spaced at 90 degrees it's called a 'crossplane' crankshaft. Yamaha use this configuration for their MotoGP 4-cylinder, 4-stroke, across the frame, engines. The sound is pleasant compared to the awful sound of a Harley. Best sounding engine of all times is the 1.5 litre supercharged, V16 BRM, closely followed by the V12 Rolls Royce Merlin.
DickG


----------



## Charles Lamont

A Deltic sounds pretty good too:



And the Cosworth DFV.


----------



## johwen

Noitoen said:


> I wonder if someone can explain. Looking at the crankshaft of a 4 cylinder engine like this one, the same as the normal full size ones, why are there always 2 pistons TDC and the other 2 "BDC"? Wouldn't it be better to "space" them 90º of each other? In this way one could have a power stroke at 90º intervals probably making the engine run more smoothly. At least it's what I think. Maybe it's easier to build them the way they do.


The reason is simple, it is to balance the rotating motion two pistons going up balanced by two going down


----------



## LSAGuy

Yamaha builds one. Here's a video;



Do yourself a favor and turn off the crappy music for the first minute and a half or so.


----------



## oliomio

Interesting video, and thanks for the noise warning. Unfortunately I was a bit slow turning it off. Horrible!


----------



## myerscw2

Are these engine plans still available for purchase?


----------



## gbritnell

Hi Meyers,
Yes the plans are still available. Send me a personal email.
gbritnell


----------



## myerscw2

Ok. I just upgraded my membership today. Not sure how to send you a personal email....


----------



## splodge

I'm interested in a set of plans, but live in the uk. Do you have them in pdf format to save on the postage etc ?


----------

