A Wallaby of my own.

[steamer]

Hmmm    I was worried about the Ali picking up on the soft crank.    Have you run with a soft crank pin on your aero engines?

Dave

[Jo]

The cranks on the Aero engines are made in EN8.

Some of the bigger engines have bronze shells on the big ends.

Jo

[steamer]

Are the pins hard?  ( EN8)

[Jo]

Its a nice free cutting high carbon steel that I use for most of my cranks which you don't need to case harden.

Jo

[steamer]

OK   Same carbon level as 1144SP.     So could run a 2014 AL like substance against it.    2024-T6 on this side of the pond is pretty common.

On the other hand.....I could just use bronze .....

[steamer]

I ran the numbers for a connecting rod load of 400 pounds   ( 500 psi Mean Effective pressure....which is WAY above anything we'll ever see by a lot)

Con rod stress is about 7000 psi.......Yield is like 35000 psi for 660 bronze.....

I'm going to stick with the bronze.

Dave

[steamer]

OK......crank is in the lathe........

[Don1966]

 

Come on Dave.......

[stevehuckss396]

Come on Dave.......

What Don said!!!!  Hahaha!!

[steamer]

Alright....got something done.


Turned the pins to .510   ( .4375 is finish)

Now I'm going to turn the mains to .5

Then back to the pins to size,

Cut the turning blocks off

Turn the mains to size.

Drill out the pins.

Cross drill for oil passages

cut the key way and thread the crank gear end.

turn the taper and cut the thread on that side....

Drill and tap for counterweights...

I tried to go the bifurcated parting tool approach, but I just couldn't get the tool to stop chattering.   I ended up with two knife tools,  a left and a right with just a wisp of a radius...

Next time I'll Mill the whole thing to rough it out and leave like .020 to turn.   It'll go faster.

We progress



Dave

[steamer]

OK    all roughed out.

All diameters are +.060"  the webs are to size.   

About .0025" run out.   I suspected it would move around a bit.   It was a good choice to rough it all over first.

[b.lindsey]

Looks good to me Dave. Keep it coming.

Bill

[steamer]

Done for the night Bill,    feet hurt.

It looks good from here too!     The worst is over I think....well there is the oil holes.....

[steamer]

I'll make up some support blocks in the morning.   they'll go in the webs and be fixed there with super glue.

Then I can finish the crank.

I also need to blank the cam with a spare.

I want to cut the taper on the shafts all at once, including the D bit for the flywheel.

so I'll have the cam blanks  ( in case I screw one up) all ready to go with the shaft tapers on them.

Dave

[Don1966]

Well that's looking good Dave. Now we can relate to what your doing buddy......

Don