917 180 degree V 12

[steamer]

iF you wanted to make some funky barrel cam....this was the tool to do it!.....Samantha bell has cut all kinds of slots, cut off 2 inch stock...ect....that sharp little parting tool was doing the hula!.....no matter...just ordered 3 carbide slitting saws.   I'll make up an arbor and we'll keep moving.     Now the good news is....the bore was cut .002" undersize.....per my discretion, and will clean up with a lap nicely.

I need to make a fixture for final boring, and some soft jaws for the mill, but we're moving.

[Admiral_dk]

No matter what - I'm sure you will end up with a nice runner - but no bets on how long it will take you ....

Pulling up a chair and     

Per

[steamer]

Thanks admiral!

[steamer]

Ok great progress today.  I'm still waiting on my saws...so no machining, but I'm nearly done with drive line.   New improved crank, resized bearings ( much more appropriately sized)    and a compression ratio check showing we're at 8.48 to 1 currently

8mm crank pin journals
5 mm wrist pin

Now we're moving here

Dave

[steamer]

A few other items I was working on today...and perhaps into tonight...  Con rod and bearings   and crankshaft assembly

the Crankshaft is ball bearing mains with plain bearing rod bearings.   Crank case pressure spray lubed with dry sump  Oil pumps off the front.

Con rods are 7075 T6 with a bronze split big end with oil grooves and reamed big end bearing on the aluminum.

Big end bronze has oil groove design from a 240 cc splash lubed 2 cylinder 4 stroke , so should be a good one.

[Kim]

You're making a lot of progress on this Dave.

In that last picture of the rod - what are the diagonal lines cut in the bearing for?  Are they for oil distribution?

Thanks,
Kim

[steamer]

Yes.    I've been doing some research on con rods used in the RC industry.    A large portion of even the most extreme application engines  ( 3.3 HP at 41000 rpm out of a 0.21 buggy engine for instance) are bronze bearing with mixed fuel/oil.   Either 2 cycle or 4 cycle.   On the OS 240  ( 24cc....BIG twin) 33mm bore 27 mm stoke.    "Mist lubed"   or fuel blow by lubed one with a bronze con rod.   The big end has this grooving with a cross groove to spread the oil coming in from the bottom hole.   Mid span it has axial grooves for lubing the sides of the bearing, and The top end just has the central groove .    CNC makes this really easy.....

I am considering putting these features directly into the rod, and dispense with a bearing shell, but as this is an experimental, I'll keep the bearing.    Journals are dead hard dowel pins  ( 52 Rc) so they should outlive me.

Dave

[dieselpilot]

What is the angled groove for? This isn't in the OS rod. I never understood the hole in the high pressure area.

[Johnmcc69]

 
 Pretty cool stuff Dave! Looks like you've done a lot of research.
 You really have to appreciate 3D CAD for projects like this. (Not that there's anything wrong with any other way...)

 

 John

[steamer]

What is the angled groove for? This isn't in the OS rod. I never understood the hole in the high pressure area.

Actually   It is.  I left a picture of the os rod in the post  The hole at the bottom of the rod  , On the cap....is actually the low pressure area.

Dave

[steamer]

Angled oil grooves are put in bearings to spread the oil over the width of the bearing.   You will find them in engines, machine tools and many other places...

Here's some examples

[Kim]

That's fascinating...
And that last picture makes my eyes go crossed! 

Kim

[stevehuckss396]

you have done a mountain of work already. Are you about ready to move forward and start making machined parts?

[steamer]

Thanks for looking in Steve. Kim, Crueby and diesel!   

Well Bubba...what do you think...would you start?      

My answer....well   Nearly
Still open issues

Taking one plug out of the heads.   It creates a great deal of variation in the compression ratio....so with 1/4-28's   1 plug per cylinder it is instead of the prototypical 2 per cylinder like it has now.   I'm going to take out the exhaust side plug so that I can put in more cooling fins and open the air flow up.  It looks constricted to me....I'd rather have an engine that I need to reduce the cooling than go looking for it!

The oil pump.  I want one.  I don't want one buried in the case such that I have to split the case to get to it like the real one.   So I'll have an oil pump and perhaps a scavenge pump, but down low, external and driven off the front of the engine.     Oil pumps job on this engine is to create a mist in the crank case.  Lube tank is external, and i'll probably recirculate with one or both pumps.   But for me, burying the pumps in the case and driving them with ity bity spur gears at 8000 rpm sounds like a bad idea....at least at 1/4 scale.

I also want to take what I've learned thus far and do a redesign on the cases.   I can simplify them and make them more straight forward to make.   Currently they are suffering a lot of CAD fixes, and the models are somewhat of a mess.   Actually, this should be pretty straight forward, as I think I know what I want.

.....Close?.....whatchathink Bubba?

Dave






 

[stevehuckss396]

I think you sound unsure so I think you should wait. If you havent decided on the crankcase yet then you cant even start. That is my first part when I build. Then I typically make the heads and oil pan. Being unsure of the head design and oil pump drive you cant do heads or crankshaft. I think you should wait until you have the entire engine in cad and you are happy with it.