Engine out practice

"Roger (K8RI)" wrote in
:

On Fri, 19 Oct 2007 11:05:32 +0000 (UTC), Bertie the Bunyip
wrote:

Matt Whiting wrote in
:

J.Kahn wrote:

It's not a problem when heating because the head expands faster
than the steel parts so the stress effects are reversed. This is
why the manufacturers have no problem with going from idle to full
power as soon as the engine will take it without stumbling. There
is no such thing as shock heating...

What about the aluminum piston in the steel cylinder?


That can happen too! But the clearances are cgrater ther than it would
be in a valve stem or head to cylinder seat.

If we had that kind of piston to cylinder clearance in an automotive
engine we'd think it was worn out. :-)) At least in the "old days".



Yes, some air cooled engines have tapered bores (when cold) to allow for
different rates of expansion in cylinder base-to-head so that it's
perfectly cylindrical when up to temp, but i don't know of any aircraft
engines that have that feature.



Bertie

"Bertie the Bunyip" wrote

Yes, some air cooled engines have tapered bores (when cold) to allow for
different rates of expansion in cylinder base-to-head so that it's
perfectly cylindrical when up to temp, but i don't know of any aircraft
engines that have that feature.

Really? I thought that they did have a tighter bore at the top. I guess I
read wrong, or remember wrong.
--
Jim in NC

"Morgans" wrote in
:


"Bertie the Bunyip" wrote

Yes, some air cooled engines have tapered bores (when cold) to allow
for different rates of expansion in cylinder base-to-head so that
it's perfectly cylindrical when up to temp, but i don't know of any
aircraft engines that have that feature.

Really? I thought that they did have a tighter bore at the top. I
guess I read wrong, or remember wrong.

Maybe. I didn't know that they did. It would make sense if they did, all
right. I don't do machining. I just run my fingers over the pretty parts
when they come out of the machine shop!

Bertie

Yes, some air cooled engines have tapered bores (when cold) to allow
for different rates of expansion in cylinder base-to-head so that
it's perfectly cylindrical when up to temp, but i don't know of any
aircraft engines that have that feature.

Really? I thought that they did have a tighter bore at the top. I
guess I read wrong, or remember wrong.

Maybe. I didn't know that they did. It would make sense if they did, all
right. I don't do machining. I just run my fingers over the pretty parts
when they come out of the machine shop!

This ought to be an easy question for someone in the group. Surely, there
is someone that does do machining on engines that hangs out here, that would
know for sure.

Anyone?
--
Jim in NC

On Oct 20, 4:41 am, "Morgans" wrote:
Yes, some air cooled engines have tapered bores (when cold) to allow
for different rates of expansion in cylinder base-to-head so that
it's perfectly cylindrical when up to temp, but i don't know of any
aircraft engines that have that feature.

Really? I thought that they did have a tighter bore at the top. I
guess I read wrong, or remember wrong.

Maybe. I didn't know that they did. It would make sense if they did, all
right. I don't do machining. I just run my fingers over the pretty parts
when they come out of the machine shop!

This ought to be an easy question for someone in the group. Surely, there
is someone that does do machining on engines that hangs out here, that would
know for sure.

Anyone?
--
Jim in NC

Ok, First off don't call me Surely. GGGG.
The concept is question is called "choke bore" and the idea is the
bottom of the cylinder that's close to the case runs at a much lower
temp since combustion happens at the other end. The top end grows at a
greater rate because of this. In theory when the engine is up to temp
the cylinder ends up being pretty straight. I have the specs around
here somewhere but if I remember correctly the bore when cold is in
the .006-.008 smaller at the top. Boring one is usually done by using
a tool post grinder and performing the taper feature is a calculated
process. Honing one with a flex hone is straight forward and easy,
using a Sunnen CK-10 or a CV-616 takes ALOT more practice...

Ben
www.haaspowerair.com

" wrote in
ups.com:

On Oct 20, 4:41 am, "Morgans" wrote:
Yes, some air cooled engines have tapered bores (when cold) to
allow for different rates of expansion in cylinder base-to-head
so that it's perfectly cylindrical when up to temp, but i don't
know of any aircraft engines that have that feature.

Really? I thought that they did have a tighter bore at the top.
I guess I read wrong, or remember wrong.

Maybe. I didn't know that they did. It would make sense if they
did, all right. I don't do machining. I just run my fingers over
the pretty parts when they come out of the machine shop!

This ought to be an easy question for someone in the group. Surely,
there is someone that does do machining on engines that hangs out
here, that would know for sure.

Anyone?
--
Jim in NC

Ok, First off don't call me Surely. GGGG.
The concept is question is called "choke bore" and the idea is the
bottom of the cylinder that's close to the case runs at a much lower
temp since combustion happens at the other end. The top end grows at a
greater rate because of this. In theory when the engine is up to temp
the cylinder ends up being pretty straight. I have the specs around
here somewhere but if I remember correctly the bore when cold is in
the .006-.008 smaller at the top. Boring one is usually done by using
a tool post grinder and performing the taper feature is a calculated
process. Honing one with a flex hone is straight forward and easy,
using a Sunnen CK-10 or a CV-616 takes ALOT more practice...

And I thought it was just my old model airplane engines and bikes that
had that feature. Who would have guessed a Lycoming could clamber to the
height of sophistication reached by Ohlsson and Rice?

Bertie

On Sat, 20 Oct 2007 12:31:57 +0000 (UTC), Bertie the Bunyip
wrote:

snip

And I thought it was just my old model airplane engines and bikes that
had that feature. Who would have guessed a Lycoming could clamber to the
height of sophistication reached by Ohlsson and Rice?

Bertie

Been awhile since Continental spec'ed a choke bore, unsure if Lycoming
ever did (I've never come across one-does not mean it does not exist).

What is curious is that on the Conti's you could "straighten out" the
choke and be within service limits in most cases.

Factory new Lycoming cylinders can tend to be a little smaller at the
upper 1/4 of the bore, but that's because the head gets shrunk onto
the cylinder after it is initially machined & nitrided. Sorta
important to check min. ring gap up there when working with a new jug.

Again, it can be a straight bore and be within new & service limits.

TC