REFLECTOR: Brian's Turbo

Fri Jan 7 20:05:17 CST 2011

Brian,

Maybe during the break while you're waiting for parts you could take a
little time and post some info (and photos?) on your turbo work.  Unless of
course it's something you'd rather not share for business reasons, etc.
Here are some facets that at least I would like to know more about:

1.	Basic engine design you started from
2.	Performance and functionality objectives for your improvements
3.	Single or dual turbo?  Piping layout for the turbo(s), wastegate and
exhaust pipes
4.	Inclusion of any induction over-pressure, or alternate air valves?
Do the intercoolers have special cooling air inputs?
5.	Automated wastegate/throttle controller design concept and some
implementation details (the version you want to end up with), i.e., the
'linear stages', 'embedded controller', etc..  Does the design also involve
mixture control?
6.	Primary electronic fuel injection system -- part of the starting
point, or something you designed?  More design detail?
7.	Any details on the electronic ignition system, if other than
standard magneto
8.	Overall engine cooling airflow concept and unique layout details

As someone (Jim Agnew?) used to always say on the Reflector -- 'curious
minds need to know'!

Bob Jackson

N2XF

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 5:54 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

Great questions.

I installed the turbo, and ran the engine with wastegate wide open.  The
performance was 50RPM static better than a carbureted/magneto Franklin with
identical propeller.  I am very happy with the performance.  First flight I
calculated a 20 degree climbout angle.  I was at 900 feet when the engine
failed, about 2500 feet from where I took off.  I don't know what that is in
FPM, but I got there stinking fast.  I kept pulling back on the stick to
keep from overspeeding the engine.  The plan was to increase prop once I
reached 1000 feet.

The initial configuration was a bit complex, so this second time I am
removing complexity and will add back those features later.
To control the wastegate and throttle, I built some linear stages, actuated
via an embedded controller.  This could be overriden by the pilot by using
the friction lock on the knobs.  These stages have been removed, and I'm
waiting on a new set of throttle/turbo cables from AS&S.

Since the primary fuel system is electronic injection, I fabricated from
scratch a completely redundant injection system.  It actually performed
quite well, but tuning on the ground is difficult.  I am removing the
automated actuating part of it, and am instead installing a needle valve
that is manually operated from the pilots position.
The original backup EFI is nice, because in an emergency, it monitored for a
power failure and engaged on that event, or a pushbutton.

At this time, I am gated on several things.  The cable install really needs
to happen before I mount the intercoolers, which prevents induction or cowl
work.
Wings are ready to mount, but we are waiting on primer.

I think three weeks after the parts are in that we'll be ready for an engine
start.  Optimistically, I'm saying March for another flight, but reasonably
would me more like June/July.

I checked the runout on the crank, and was very pleased to measure .0005"
TIR.  The manual says I'm allowed .008" so that's pretty good.

On 1/7/2011 4:17 PM, Bob Jackson wrote: 

Sorry, Brian!

I forgot about your first flight adventure.  Don't feel bad, almost all of
us have done something.  I had engine problems (turned out to be my own
engine control mis-management) and ran off the end of the runway when doing
simulated power off landings.  And my A/C partner collapsed the nose gear
(poor technique and a suspect weld) and slid down the runway a 1000 feet
grinding away the bottom of the nose!

I'm sure your fix would do the job, I'm just concerned about the small-area
steel-to-aluminum contact space.  But probably for no reason.

I remember you also had a pretty fancy turbo design.  How is that working
out?  When do you think you might get back into the air?  We fiddle-farted
around for ten years to complete, then another half-year off repair the hole
in the nose after the NG collapse.  Nobody likes the 'when are you going to
fly' question!

Thanks for all you do operating and maintaining the Reflector,

Bob

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 4:20 PM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

I think it's safe to say I have about .05 hours of airtime on it.

That would be the first flight, and subsequent off field.  However, over
years of airplane work, it's been tight.

On 1/7/2011 12:35 PM, Bob Jackson (Jax Tech) wrote: 

Nice design and approach!  How many hours do you have on it?  

Don't you still have concerns about the effect on the softer aluminum of the
hard steel bolt?

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 1:02 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

There has been little discussion on a fix.  My solution involves making a
saddle, I'm not sure if it's what the factory does or not.

I think the tubes are 1/2", so I bought some 1/2"ID, .25" wall aluminum
tube.
With about 2" of stock, I first machined a flat on opposing side, leaving
about 1/8" thickness.
Next, cut the tube in half along a plane parallel with the two flats.
Take the two halves, and place them flat to flat, drilling a hole for the
bolt.  The tubes can now be cradled in the saddle.

The flats help support the torque transmitted to the two tubes at right
angles.  For extra smoothness, use a thin teflon washer(or sheet) between
the flats.

On 1/7/2011 11:13 AM, Bob Jackson wrote: 

We've been flying for a couple of years and now have 300+ hours on the
plane.  When we started doing some formation flying recently I began to be
aware that we're developing stick slop -- it's not what you want flying
close formation, or when landing or anytime you need small corrections and
fine attitude control.

When we built the plane we were leery of the standard steel AN3 bolt that
joins the bottom of the aluminum stick stub and the aileron/elevator torque
tubes) -- even when improved with the U-shaped steel reinforcing collar that
the factory started shipping.

In our case, we know that nearly all of our stick slop comes from this
mechanical connection between the stick's torque tube and the aileron and
elevator torque tubes.  We've been on the Reflector for 12 years, but
haven't heard much, if any talk about this problem and improvements that
builders have made.

The question is:  do any of you have good fixes for this connection that
eliminates stick slop?

Thanks,

Bob Jackson

N2XF

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