Auto conversions & gear boxes

On Tue, 09 Mar 2004 03:18:59 GMT, Peter Dohm
-KNOW wrote:

At the moment, the Geshwender drive (which is back in production despite Mr G's
death) looks like the most reliable scheme for much more than 100 horsepower,
any may still be the best value in the long run.

I agree, but add that this psru was originally designed for high
output engines, engines that start with around 400 horsepower.

For those interested, the reason Fred designed the psru in the first
place was to provide a less expensive engine alternative for crop
dusters. The engine he used was a Ford big block V8. I think that
smaller psru's may be available now but I haven't checked for a while.

When I called him to talk about his psru a year before he died, he
talked me out of using it because it was overkill to use that psru on
an engine putting out only 190 or so hp.

Corky Scott

Corky Scott wrote:

On Tue, 09 Mar 2004 03:18:59 GMT, Peter Dohm
-KNOW wrote:

At the moment, the Geshwender drive (which is back in production despite Mr G's
death) looks like the most reliable scheme for much more than 100 horsepower,
any may still be the best value in the long run.

I agree, but add that this psru was originally designed for high
output engines, engines that start with around 400 horsepower.

For those interested, the reason Fred designed the psru in the first
place was to provide a less expensive engine alternative for crop
dusters. The engine he used was a Ford big block V8. I think that
smaller psru's may be available now but I haven't checked for a while.

When I called him to talk about his psru a year before he died, he
talked me out of using it because it was overkill to use that psru on
an engine putting out only 190 or so hp.

Corky Scott

I agree about it being overkill. An it is not cheap either. However, it looks
like something you can trust.

It's really an interesting dilemma that I will have to face when I get ready to
build. If you don't require true short field capability, and only need a two
seater; you can give up a little power and thrust, and build a v6 version of
Steve Wittman's Tailwind installation.

I admit that I am willing to give up a lot of "utility" for the few features
that I think I need. I really don't consider landing speed very important, but
want adequate cabin width at my own elbows and shoulders.

The basic point is that I believe that I can power my first project with direct
drive. Probably an engine in the 3.8 to 4.3 liter displacement range turning a
56 to 60 inch diameter prop and developing 130 to 150 horsepower. That should
be enough for a cruising speed of about 130 kts tas.

To be really blunt about it, I could probably design a better airplane with
similar performance around a 110 hp corvair engine--if I knew of a source for
*new* heads and crank cases.

I also recognize that such an installation won't work on a Christavia MK4, which
needs a longer prop. Therefore, you really don't have a choice. You are
building the airplane that those 2400 to 2500 rpm engines were designed for! If
you use an automotive conversion, you need a psru. Hypothetically, you could
get about 170 hp from a 350 cid v8 turning a 72 inch prop at crankshaft rpm; but
you would be lugging the engine, so the smaller engine with the psru would last
longer and would still be at least 50 pounds lighter after allowing for the
drive shaft and thrust bearing adapter on the v8.

Peter

On Wed, 10 Mar 2004 01:27:46 GMT, Peter Dohm
-KNOW wrote:



I also recognize that such an installation won't work on a Christavia MK4, which
needs a longer prop. Therefore, you really don't have a choice. You are
building the airplane that those 2400 to 2500 rpm engines were designed for! If
you use an automotive conversion, you need a psru. Hypothetically, you could
get about 170 hp from a 350 cid v8 turning a 72 inch prop at crankshaft rpm; but
you would be lugging the engine, so the smaller engine with the psru would last
longer and would still be at least 50 pounds lighter after allowing for the
drive shaft and thrust bearing adapter on the v8.

Peter

I'm building a Christavia Mk4 and have the Ford 3.8 installed in it
right now. The psru I'll be using was one of the products put out by
NW Aero before Johhny Lindgren acquired the business. Johhny made the
psru for the Ford V6's available for a while but does not do so any
longer because very few people seem interested in it.

He does have psru's for Chevy V6's and V8's though and I bought all
the things I need for my engine from him. Things like the camshaft,
distributer, alternator and brackets, and the proper sized pulleys to
drive everything. He can still get them.

The original psru has undergone considerable modification and looks
like a very nice unit. The top and outer drive cog bearings are now
lubricated by an enclosed oil bath, rather than by grease that must be
injected periodically by the owner.

There was a failure written up by a guy who had a Chevy V-8 in his
Lancair. The drive cog bearing seized and the belt broke. He landed
short and the airplane flipped over when the wheels dug into the soft
ground but the guy was ok. Saw some pictures of it in Contact!
magazine. The drive cog bearing had overheated and seized and the guy
admitted he did not really know how much to grease it, or how much to
put in while greasing and apparently hadn't for a while.

I'd call those bearings pretty critical parts and I'd want to have
maintenance logs telling me exactly when they were last greased.

The engine, by the way, continued to run fine and the owner was
planning to get the updated psru, which he felt was a better design.

The Chevy V6 is a pretty good engine and has a good track record when
used in airplanes but it's considerably heavier than the Ford V6
because it has cast iron heads, intake manifold and timing chain
cover. All the afore mentioned parts are aluminum in the Ford, which
makes it the lightest V6 of that type of design in the US.

You can buy all kinds of aluminum parts for it (the Chevy) to lighten
it up, but the aluminum heads are competition models and the intake
valves and air passages are designed for max power at high rpm and
they don't adopt very well to moderate output levels. You can also
buy aluminum intake manifolds for it and probably aluminum oil pans
too. It's just that each purchase takes you beyond the cost of the
original engine. I've said this before but if money were no object,
or if I had no mechanical background, I would not be converting an
auto engine. I'd just bite the bullet and spend the $10,000 to
$15,000 it takes to get a reasonable, well maintained Lycoming or
Continental. I still think it's incredible that engines can cost that
much, but they do.

Corky Scott

On Wed, 10 Mar 2004 14:29:29 GMT,
(Corky Scott) wrote:



He does have psru's for Chevy V6's and V8's though and I bought all
the things I need for my engine from him. Things like the camshaft,
distributer, alternator and brackets, and the proper sized pulleys to
drive everything. He can still get them.

Clarification: Sorry, this paragraph is confusing. What I meant to
say is that Johnny does not offer the psru for the Ford anymore, but
he does still offer some parts for it. Or at least I was able to get
them from him.

The distributer is machined for him and he installs dual sensors so
that you can run two electronic ignition systems. The distributer is
set up with advance weights so that the engine can be started at zero
degrees BTDC and then advances to it's running timing setting after
the start. This makes for easy starting.


You can buy all kinds of aluminum parts for it (the Chevy) to lighten
it up, but the aluminum heads are competition models and the intake
valves and air passages are designed for max power at high rpm and
they don't adopt

Adopt should be adapt.

very well to moderate output levels. You can also
buy aluminum intake manifolds for it and probably aluminum oil pans
too. It's just that each purchase takes you beyond the cost of the
original engine. I've said this before but if money were no object,
or if I had no mechanical background, I would not be converting an
auto engine. I'd just bite the bullet and spend the $10,000 to
$15,000 it takes to get a reasonable, well maintained Lycoming or
Continental. I still think it's incredible that engines can cost that
much, but they do.

Corky Scott

Corky Scott wrote:

On Wed, 10 Mar 2004 14:29:29 GMT,
(Corky Scott) wrote:


He does have psru's for Chevy V6's and V8's though and I bought all
the things I need for my engine from him. Things like the camshaft,
distributer, alternator and brackets, and the proper sized pulleys to
drive everything. He can still get them.

Clarification: Sorry, this paragraph is confusing. What I meant to
say is that Johnny does not offer the psru for the Ford anymore, but
he does still offer some parts for it. Or at least I was able to get
them from him.

The distributer is machined for him and he installs dual sensors so
that you can run two electronic ignition systems. The distributer is
set up with advance weights so that the engine can be started at zero
degrees BTDC and then advances to it's running timing setting after
the start. This makes for easy starting.

You can buy all kinds of aluminum parts for it (the Chevy) to lighten
it up, but the aluminum heads are competition models and the intake
valves and air passages are designed for max power at high rpm and
they don't adopt

Adopt should be adapt.

very well to moderate output levels. You can also
buy aluminum intake manifolds for it and probably aluminum oil pans
too. It's just that each purchase takes you beyond the cost of the
original engine. I've said this before but if money were no object,
or if I had no mechanical background, I would not be converting an
auto engine. I'd just bite the bullet and spend the $10,000 to
$15,000 it takes to get a reasonable, well maintained Lycoming or
Continental. I still think it's incredible that engines can cost that
much, but they do.

Corky Scott

It looks like you've made the right choices for the type aircraft, and
I'm eager to read about the flight experiences.

Peter