[Ken_Shea]

Ken,
in order to have them done already I would have to break out this bad boy and give it a wave along with a few top secret spells.

Ha-Ha, I have one of those but don't normally let any one see it

[cforcht]

LOL I don't usually let anyone know I have a magic wand either. cuz if they knew they'd be asking for more miracles than they do already.

[cforcht]

All of these rotor related pics are for you Ken.
heres the first mill op. this is so I can make sure both ends are aligned

heres what I did to them next after putting the flats on one side of them

[cforcht]

each end was dialed in so the pattern was true to the bore

[cforcht]

heres the fixture I made so I can locate the lobes.

[cforcht]

here the part is on the fixture

[cforcht]

heres what it looks like after running the first program which I call the "valleys" of the rotor. the other would be the peak which is not done running yet. I did the valleys first because it was the bulk of the material to remove. the peaks have very little left on them once the valleys are done.

[Ken_Shea]

Great pics Craig,
I know they take a lot of time to take and process, thank you!

Those rotors are looking real good, you've made a lot of progress on them in a very short while considering everything had to be thought out.

[cforcht]

heres the rotor off the machine

[cforcht]

another view

[cforcht]

here it is liberated from the excess material

[Ken_Shea]

Craig,
A bit confused on the operations, you rotated it three times then?

[cforcht]

my shaft that I am using is not quite straight. it does spin in the case but not as freely as I would like. it has a few hangs. but there are things I can do to fix that. I need some ultra thin washers to space the rotor from the end plates too. a couple thousandths should work.

[cforcht]

actually it was rotated 6 times altogether. once for each "valley" and once for each "peak" or lobe if you will

[Ken_Shea]

ok, you indexed it on the end pins then and not the block .

[cforcht]

yes exactly. that way everything stays in relationship

[cforcht]

gotta say though it looks like the real thing

[cforcht]

I was rummaging around and found a piece of shafting that was the right size. made a world of difference on the rotor to housing clearance. I can spin it with the shop air in the housing. however this is just a single rotor so far not meshed with another rotor yet.

so I need opinions here.
one: leave it as is and hope the rotors mesh together without binding? which they do in the CAD world.

two: adjust the program to take a couple extra thou off the surfaces so it all meshes freely and sacrifice a little "boost" and fewer headaches

thing is I had a book long ago on how to set up a super charger. it is a very long and complicated process to get all the clearances right for optimum boost and minimal loss.

let me know what ya think.

[dynosor]

leave it as is and hope the rotors mesh together without binding? which they do in the CAD world.

two: adjust the program to take a couple extra thou off the surfaces so it all meshes freely and sacrifice a little "boost" and fewer headaches

I presume the two rotors are geared externally rather than that one aluminum lobe drives the other internally?

Could you leave them tight and lap them against each other with a mix of lithium grease and Brasso or perhaps something a little more aggressive? I would turn them over very slowly for this operation initially, preferably by hand so that you can feel the effort go down - if it goes up, bad things are happening and you need to stop.

Even if geared, I presume lash opens if you rotate in reverse and then the lobes can make hard contact?

What happens to the total clearance when the blower gets hot in use? If clearance goes negative for a 100 degree F rise in temperature then you need to machine in more starting clearance – the blower is mounted on top of a hot engine and the work it does will raise the temperature a little more. The metal volume of the impellers probably needs to be reduced if there is risk of "going solid" - the casing's thermal expansion probably simply adds clearance.

[TarHeelTom]

two: adjust the program to take a couple extra thou off the surfaces so it all meshes freely and sacrifice a little "boost" and fewer headaches

thing is I had a book long ago on how to set up a super charger. it is a very long and complicated process to get all the clearances right for optimum boost and minimal loss.

let me know what ya think.

Are you planning on running this engine in a dragster? In competetion?

If not, get sufficient clearance and don't worry about it.

Tom