REFLECTOR: FW: Brian's Turbo

Wed Jan 12 14:17:04 CST 2011

Bob,

10.5:1 compression is standard for a Franklin so turbo normalized does not increase the detonation risk.

Larry Coen
N136LC

From: Bob Jackson (Jax Tech) 
Sent: Wednesday, January 12, 2011 8:24 AM
To: 'Velocity Aircraft Owners and Builders list' 
Subject: REFLECTOR: FW: Brian's Turbo

Looks like a very nice layout, Brian -- I like the compact, minimal induction plumbing design achieved with the way you've located the intercoolers on the bottom of the cowling near their cooling inlet airflow.  Are you concerned about having the turbo sort of 'trapped' in the relatively dead airflow space between the engine and firewall and with transferring it's heat out of the engine compartment efficiently?

I assume that since it's a single turbo, then there's a single wastegate bypass type arrangement near where the exhaust from each side funnels into the turbo, correct?  Any photos handy of the inside layout?  Are you concerned about increased detonation risk with the high compression cylinders?  How will you manage that risk?

Thanks for the info and photos,

Bob Jackson

N2XF

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From: Brian Michalk [mailto:michalk at awpi.com] 
Sent: Monday, January 10, 2011 12:22 AM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Brian's Turbo

There's lots of information to address your questions.  I'll start on them, and send them out as I get time.

  1.. Basic engine design you started from 
    1.. It's a stock Franklin.  6A-350-C1R, 10.5:1 compression.  I had the idea that someday 100LL would go away, so with the turbo in there, I could convert to low compression pistons and perhaps reprofile the cam to better suit turbo operation. 
  2.. Performance and functionality objectives for your improvements 
    1.. Turbo normalize only.  I'm not looking to exceed TBO horsepower. 
  3.. Single or dual turbo?  Piping layout for the turbo(s), wastegate and exhaust pipes 
    1.. Single turbo.  From memory, I believe it's a T06, Airresearch. 
    2.. Intake air 
      1.. armpit scoop from the pilot side 
      2.. Bosch 3" throttle body 
      3.. turbo situated slightly to the right side such that axle is pointing right at the armpit scoop, and the compressed air exits center of the firewall, pointing down 
      4.. Intercoolers.  Two RJR (I think) motorcycle intercoolers welded to a center plenum that goes to the turbo.  Air makes a right angle turn out each side of the intercoolers towards the outside. 
      5.. intake manifolds that pick up from the intercoolers near the firewall an go the all of the cylinders aft.
      The intercoolers get a fairing so it's all smoothed out.  Not shown in the pics below.

On 01/07/2011 08:05 PM, Bob Jackson (Jax Tech) wrote: 

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

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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

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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?

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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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