Conference vmszoo::rc

    
    	There is some truth to the fact that retracts are a problem
    in grass. I find the problem to be more nose gear steering that
    gear folding up. I've used goldberg,IM, Royal and now B & D
    retracts. I have found that the B&D are the best. They are by far
    the most strong and they have the least critical throw setting
    of all the gear on the market. The use of mechanical versus
    air/gas is primarily driven by what plane the gear is going into.
    Most scale ships use air/gas because the retract rate and sequencing
    can be easily modified to act like the real ones in the real ship.
    Most pattern birds these days are going for the mechanicals because
    of their simplicity (as apposed to air) and their realative weight
    as apposed to air. Why are you considering retracts? How long
    have you flown? What ship are they going in?
    
    
    						Tom

RE .1:

    I'm looking at something along the lines of a Phoenix 60 as my
    winter project.

    I've been flying RC since about '74 (with a 5 year break for a
    wife and kid) with a BUNCH of CL/stick&tissue/etc before that.
    I'm on my 7th RC plane (a SIG Kougar/FOX .45)

    The biggest reason that I want to use retracts is it's just one the
    things that I haven't done yet and I want the experience. Yeah, it's
    more of a hassle than fixed gear but playing with nifty stuff is
    what hobbys are all about, right?

    OK Good I was concerned that you might have been a newcomer looking
    to build that WWII bird.   There are a few Phoenix plane around.
    Which one exactly were you interested in building.  If it's one
    of the semi built jobs they're design might have restrictions as
    to the type or manufacturer of retracts that the plane was designed
    for.  Mechanicals are realitively simple. There is a lot of building
    pre work that goes into a good retract set up.  Some ships actually
    use two retract servos. One for the mains and a second for the nose
    gear. When you decide what retract that your going to use buy some
    replacement steering arms etc. You'll find that in most designs
    this is one of the weak points. I myself like the B&D retracts.
    They are mechanically simple. Made on some type of nylon reenforced
    material and they aren't critical to servo throw adjustments. There
    is a minimum of 1/8 to 1/4 of an inch of lock in the up and the
    down directions. 
    
    							Tom

Why don't you make a tail dragger as the first exercise. I once had a Don Lowe 
Phoenix 8 with OS61-VF ABC, Pipe and servo operated Main Gear. It was reliable, 
easy to install and the total weight was less than 8lb.

As Tom said the nose gear is always a drag, it requires a lot of maintenance 
adds weight and increases frustration disproportional to it's benefit.

John.

    
    If the ship is to be a competiitive one I would go with a trike
    gear set up. Even with the bother that a nose gear can be this
    outweights itself in the face of consistant take off's and landings.
    Each bounds during a landing is a 1 to 2 point reduction. They
    score landings and takeoffs equally as they do flying so why give
    points away. If on the other hand your not into competing then a
    tail dragger set up in the least frustrating retract set up. I have
    a Dolatel being finished right now and that's a taildragger. I've
    been thinking of throwing together a ship that I'll put on skiis
    to practice with this winter. 
    
    					Tom

Thanks for the comments, great stuff. It never occured to me to do a
taildragger, but I think i'll go ahead and stay with a trike.

GES

         This topic has spurred my interest in retracts.  I'm thinking
    about installing them in a Super Kaos 60 that is currently flying
    with fixed gear.  I will take the advice and go with B & D mechanical
    retracts.  Should I use two servos or one?  Belly mount or firewall
    for the nose gear?  Will Kraft kp15 servos work or isn't there enough
    throw?  Am I nuts???  Should I forget about doing this to a plane
    that already is built and wait for my next project!!

    
    	Lets see,
    
    	1, Depends on the relationship of the wing center line and the
    nose gear actuation. Aslo depends on the planes overall weight goals.
    Most times one servo can be used. 
         
    	2, B & D can be mounted either belly or firewall. I like firewall.
    
    	3, Only use "retract" servos.
    
    	4, NO
    
    	5, Leave well enough alone. It's difficult enough the first
    time on a new ship let alone on that is already built. Unless you
    have no problem with ripping apart the bottom of the wing and the
    chin block section of the fuse.
    
    
    
    	If you trying to get your Kaos to fly better and think that
    retracts will help(which they will) an alternative on your fixed
    gear ship is to find and use some Kraft slim line wheels. The smallest
    ones that will suit your flying site.
    
    	Also retracts are actually easier in a foam wing than in a built
    up wing.(My opinion.)
    
    
    							Tom
    
    	3, 

    
    	You can also clean up the Kaos with lighter wheels (Dave Brown
    foam type) and wheel pants.  Bet it'll do better than with the added
    weight of retracts and those huge, turbulence-generator wheel holes.

    Al Casey  (RC-AV8R)
    PNO::CASEYA
    Phoenix  PNO/D7
    
    Having only discovered RC notes today, I'm really green at using
    the forum (help/suggestions welcome) but I've been an aircraft 
    modeler for nearly 40 years, the last 24 of which have been in R/C
    so, if it's permissible, I'd like to offer my 2-cents worth on the
    subject of retracts.
    
    My primary interest lies in WW-II scale fighters (my scratchbuilt
    MiG-3 has placed in every contest entered, won two, qualified for
    3 Scale Masters Championships-placing 10th in the last one) so I
    feel qualified to comment, having seen most, if not all, of the
    makes/models/brands of retracts from Cletus Brow's crankcase pres-
    pressure powered pneumatics of 20+ years ago to present.
    
    My personal opinion is that the Rhom-Air pneumatic system is just
    about the best thing to come down the pike since pull-tab beer cans.
    They're strong (my MiG weighs 12 lb.-no failures in over 100 flights)
    reliable, extremely easy to install (no special servos or complex
    linkages required), have the lowest chordwise dimensions and, most
    importantly, are so simple as to be nearly idiot-proof.
    
    I prefer NOT to use freon or other gas propellants as air is free
    and these gasses tend to dry out the O-ring seals.  Also, these
    kind of supplies have a nasty habit of running out when you're on
    the field and the nearest store is a half-days drive away.  I sim-
    ply use a Sonic hand-pump...no sweat, air never runs out.
    
    To expand a little on the simplicity angle, what could be easier?
    You simply bolt them in place, run the air tubing through ANY con-
    venient route, pump 'em up and you're all set.  The smallest servo
    you have will suffice to operate the air-switch and, owing to this,
    I'd have to believe Rhom's are the lightest all-up weight to boot.
    
    As noted in one of the previous replies, the retract/extend speed
    can easily be regulated by use of restrictors or, easier yet, with
    wheel collars on the air-lines.  Incidentally, ALL air connectins
    should be saftied with a drop of CYA to prevent them being blown
    off by over-zealous pumping.  Our dessert climate also adds the
    factor of heat induced pressure build-up in the system but, again,
    using a common sense approach to things, I've had ZERO failures
    of any kind in well over 100 flights on a sophisticated Masters
    class scale bird so I swear by the whole concept.
    
    One of the other replies suggested you use a taildragger set-up
    and I heartily agree.  The benefits are manifold: reduced weight,
    less gear-down drag, simplicity of installation and the advantage
    of being able to install the air tank in the wing, thereby elimi-
    nating the need for troublesome quick-disconnects to name a few.
    I should admit up-front to a predjudice for taildraggers in the
    first place but it WOULD simplify the task immensely.
    
    Before signing off, a little personal background:  as stated earlier,
    I'm a lifelong modeler, belong to the Sun Valley Fliers and, along
    with Kent Walters and Bob Frey, am a co-founder and two-time past
    Commander of the One-Eighth Air Force, the Phoenix based scale group
    that hosts two enormous all-scale Fly-In's yearly.  Our meets have
    been covered nationally by RCM, Scale R/C Modeler, Model Airplane
    News, Model Builder and others over our 10 1/2 year history.  Hope-
    fully you've seen coverage of our meets in one or more of these
    magazines.                             
    
    At any rate, if you haven't already started installation or made
    a firm decision, give the Rhom-Air system some thought.  I love
    'em and I think you will too.
    

    
    	I would like info regarding the weight difference between tri-gear
    fixed and retracts like Rohm.  Again I'm trying to keep the weight
    down on my first ducted fan project and need to weigh all the
    variables.
    				Thanks TOM from PA

OK, I'll give it a shot, Chris.  "All" retracts work similarly, from the mechan-
ical perspective.  They all have a variation of the same basic scheme, that of a
pivoting trunion block, frequently aided by a cam-over-center spring arrangement
to reduce actuating load to an acceptable level in the retract [gear-up] mode.
With the exception of the Rhom-air unit, all retracts have an up-lock and down-
lock which is normally engaged at the extreme ends of actuator throw.

The primary difference between strictly mechanical [servo-operated] versus pneu-
matic [air] systems is the manner in which the trunion block is actuated.  In 
the mechanical setup, a servo of sufficient strength and throw [normally called
a 180-degree servo] is connected to the retract unit via hard [music] wire link-
age which may or may not require bellcranks, depending on application and setup.
The pneumatic unit has an air cylinder/piston attached directly to the retract's
trunion block and is actuating by either supplying or exhausting pressurized air
to the piston assembly.  It should be undersrood that any mechanical retract can
be converted to pneumatic by simply installing a Sonic-System air cylinder/pis-
ton assy. adjacent to the retract unit and connecting the cylinder's output 
shaft to the retract's actuating arm/lever/shaft or whatever.

I should mention that I'm partial to the Rhom [pneumatic] system due to the sim-
plicity of installation and the painlessness of setting them up.  In a mechani-
cal system, length/shape/etc. of the wire linkage is critical to proper opera-
tion and, if not "just" right, causes many headaches in the retract, or MUCH
worse, the extend cycle.  Nothing's more aggravating than to scrape a quarter-
inch off the belly of yer' shiny bird `cause "the d**n gear wouldn't come down.
And, oh yeah, make a hard landing and that critical, "just right" mechanical
link-up you spent "hours" achieving in the workshop frequently goes right down 
the toilet!  Now, you cuss/sweat over it at the field or take it home in order
to realign the linkage.  No thanks!

There are NO linkage throw adjustments required to install a Rhom-air system.
The unit is built to utilize full throw of the piston and all that's required
to attain this is to supply air pressure to either side of the piston.  What
could be simpler?  Bolt the unit(s) in place, attach the airlines from the
"conventional" servo operated air valve and yer' all set.  Of course, by now,
you have also installed the air tank and fill-valve and have them connected
to the air switch also.  Get out yer' handy-dandy air pump, pump up the tank 
and away you go.  Normally, after a hard landing, all you "might" have to do is
straighten the strut and yer' off to the races again.  One disadvantage to the 
Rhom gear is that it has no up-lock...it relies on air pressure to hold the
gear up in the wheel wells.  No "real" biggie but, occasionally, you might no-
tice the gear sag out of the wells at the bottom of a loop [or in some other 
high-G maneuver] then pop back in.  However, the "no up-lock" feature "can"
be an advantage in that if there's even the slightest pressure remaining in the
air tank, the gear "will" come down AND lock!  Good insurance, I'd say.

Well, that's my $.02 worth.  I concede that there are a lot of good points for
mechanical retracts also and many flyers use them with success.  These are just
some of the reasons for my "personal" preference or the pneumatics.

Adios,	Al

    Al,
    
    I can certainly see the advantages of air retracts.  Much less hassle,
    it appears.  My concern is the weight.  I figure fixed gear is
    lightest, then mechanicals (maybe not if two servos are needed),
    and last air (due to air tank, tubing,etc...)
    
    Can you give us a guestimate on the weights.  It will be critical
    in a .45 size pattern plane.
    
    Also, are you saying rhom's lock in down position?  I've seen several
    nose gear collapses due to some hard landings.
    
    Chris

    Chris,
    
    It's just a SWAG, but I think the weight difference between mechanical
    and pneumatic systems is negligible.  I might even suppose the Rhom
    system "could" be slightly lighter but can't substantiate that suppo-
    sition.
    
    Rhoms are smaller/lighter, individually, and the air tank, fill
    valve and air switch weigh virtually nothing.
    
    Yes, Rhoms have a verrry positive down lock.  Of course, you "can"
    cause "any" lock to fail if you thump `em hard enough and some modelers
    seemed destined to be the acid test for "any" system/hardware/device
    known to man in that they find it impossible to follow directions/
    advice and or do a reasonably clean installation.  Do a good clean
    job of installing them and don't abuse them and Rhom's will last
    a trouble-free lifetime.
    
    Incidentally, why does this guy you mention land on the nose wheel??
    properly done, he should touch down nose-high and stalled, if not
    nearly so, and run along on the mains `til the nose comes down by
    itself or he "gently" lets it down by relaxing the back-pressure
    on the elevator stick.  If a guy consistently lands on the nosewheel,
    bending the strut and/or futzing up the steering linkage, a retractable
    nosewheel hasn't a prayer under his guidance, no matter "what" kind
    it is.
    
    Adios,	Al

    Al,
    
    I guess if I keep hear'n Rhom long e'nuff, I'll shell out a 100
    smackers for em'. 
    
    The guy I am talking about, is our infamous Ducted Fan Ace.  The
    nose gear does'nt always give, but seems to be a frequent occurence
    on his Mig 15 and his F-20.  He lands them mains first,  then I
    realized that these things land like rockets and he always puts
    them in the grass.  It probably is the combo of grass, speed and
    weight of the DF's that causes this.  
    
    So Al, your Rhom's are still sacred.  What'cher 2 cents on Spring
    airs?
    
    Tom T.,  If you read this, how bout some info on MK's, like your
    opinion of them and does INDY carry them?
    
    Chris

    
    	I don't know if INDY carries MK retracts. In the past I have
    had MK,IM,Goldberg and Royal mechanical retracts. As Al stated
    the linkage set up in these is most critical. Typically you  will
    have almost no issue with any of the mains. The linkage is easist
    of t he three to set and because the cam within the retract is set
    at 90 degrees to the load the lock doesn't see the force of landing
    like the nose gear does. Most often when I've seen a retract fail
    it has been the nose gear. Again this is due to set up and how the
    gear see's the load. The Cam/lock is directly in line with the applied
    load and hence the need for a complete locking is required to keep
    it from collapsing.
    With this then history I had been looking for something better.
    Two years ago I met Dean Papas at a meet and he introduced me to
    a retract named B & D.  Remarkably simple and very positive in both
    the up and the down lock. Since then I have never had a failure.
    The gear is made from a composite material. The lock section of
    the gear is 1/4 of an inch in duration in both the up and the down
    positions. This means that the throw of the servo and be off +-
    1/4 inch and the gear will still actuate and lock. 
    
    I like Mechanical.  Chris, your choises are simple.
    
    	1, Buy MK mechanicals
    
    	2, By Rhom's
    
    	3, Buy something else and have to rework your retract mounting
    plates.
    
    I'm biased and would do the rework for the B&D. I'm however not
    you. 
        Oh, B&D makes an air retract the is the mechanical gear with
    an air cylinder to actuate it built right in. However you would
    still have to rework the mounting plates in the wing.
    
    
    						Tom 

    Tom,
    
    Thanks for the response, I find myself playing a game of mental
    tug of war.   I like the simplicity of air retracts, but not the
    price.  I think the final decision will come down to what's the
    lightest setup.   It seems to me that two servos (special retract)
    would be necessary for Mechanicals.  Looks like more $ and lbs.
    to go that route.  Oh well,  I have all winter to decide.
    
    Thanks,
    Chris

    Chris,
    
    When you consider the cost of the extra, heavy-duty, 180-degree
    servo(s) [2- required for tri-gear, the $90.00 for a set of Rhom's
    seems like a bargain; $40-$60 for a set of mechanical gear "plus"
    $80-$120 for the retract servos = $120-$200 for the mechanical setup
    and $250 isn't out of line if you want to go "first-cabin."
    
    If cost is another consideration, again, I recommend the Rhom system.
    Simplicity + light-weight + low [total] cost = one helluva deal
    in my book.                               
    
    Adios,	Al

    Al,
    
    You ol' dawg!  I have decided that if this bird gets retracts, they
    will be Rhom's.  I did some figuring over the weekend on cost and
    ease of installation/maintainability.  And you're on target (as
    usual).
    
    Thanks for the advice/consouling/sanity_check,
    
    Chris
    

    Al, You mean you never hesrd of running trike gear with one 180
    degree servo. SHAME SHAME SHAME. Hey, 2 oz's are 2 oz's. It really
    not that difficult. In my book that puts mechanicals at $ 40-60
    + 40 for a servo =  $ 80-100.00. Whatever.....
    
    
    
    						Tom

    Tom,
    
    Yer' right...never heard of it.  But, then again, having never had
    the need to setup anything more than a conventional-gear system,
    I guess I never had any reason to.  How's it done?...servo mounted
    in wing with detachable nose-gear linkage??   Adios,	Al

    
    
    You know Al, Your not a dump:-) as Dan Snow says you are:-))
    
    Yes, servo in wing with detachable hookup to nose gear. Quite
    simple as a matter of fact. On my brushfire I used to have a clevis
    with lock nut and rubber collar at the nose gear and a ball link
    at the servo. When I was done with flying I would take the wing
    off at take the nose gear wire off onf the servo and stick it inside
    the fuse of the airplane. Never had a bent wire this way. It's the
    lightest trike gear set up going. When I first installed this set
    up I was concerned that the srevo wouldn't be enough. No PROBLEMS
    
    
    
    
    						Tom

I like rohm airs too.

They are easy and pretty much trouble free, however:

I do a couple of small modifications to them for my intended usage
which is pattern flying.

   a) In pattern you don't want a plane to waver down the runway
on the takeoff roll and there are no manuvers that are judged that
require a 180 deg turn on the runway.  Because of this it is common
to disable the nose wheel steering by drilling and taping a hole
in the nose gear trunion and installing a set screw to lock the 
strut bearing in place.  Look at how it is done on the mains to
get an idea of where to put the set screw hole.

   b) The four little screws on each side that hold the side plates
to the aluminum body tend to fall out and get lost.  I re-install
these with lock-tite before installing the retract in the plane.  If
these screws get loose the alignment of the air piston with the
actuator suffers and in worst case can cause enough binding to prevent
full travel of the actuator.  This will defeat the down lock with
obvious results.

   c) The main gear struts tend to bend back with hard use such as 
flying off of grass or a bad landing or or or.  They can be bent foreward
again but this gets old quick.  The worst case here is that if you don't
notice this, take off and retract the gear, the main wheel(s) lodge
themselves against the cut out for the wheel well and then they don't
come back down.  If you have this problem in flight, a lot of times
a little externally applied force such as a tite inside loop or sudden
pull up will get the wheels out of the wells and then they go down and
lock if there is even the slightest amount of air left in the system.
If mechanicals don't come down for some reason, they usually stay that way.
To solve this problem, I have a coule of sets of rohm airs set have been
modified to accept the IM struts which are slightly larger diameter and
have a multi turn spring coil.  To do this you have to ream out the hole
in the trunion to accept the larger wire.  This is the cadillac solution.
Second best is to cut as much material as possible from the TOP of the rohm
air strut so that the maximum bending moment will be more centered on the 
spring coil of the strut.  Make sure you check up and down positions before
you cut the wire.

Just a coule of other comments here.  With rohm airs you can use the smallest
and lightest of servos to actuate the gear.  In fact you don't really need
proportional/progressive control of this function.  ?Anyone know of an 
acutator that doesn't use a servo?  Also, I would not take all winter to 
make this decision as building a wing without your retracts on hand is like
installing a firewall without your engine.  I also like to glue a round
piece of 1/4" radio foam into the upper surface of the wheel well to absorb
some of the shock of the wheel retracting into the wheel well.  Rohm airs
transit the retract/extension cycle very fast unless the air flow is
restricted and for this reason do not produce a very scale like effect if
this is important to you.  I spray a litle silicon lube into the air system
and on the external mechanics from time to time just to keep things moving
freely.  This works well, helping to preserve the rubber seals and is
non-greasy and so it doesn't soak into the plane, loosen monokote, etc.

Have fun!!
ron

There have been several older notes in which Tom Tenerowicz recommends
the use of B&D Mechanical Retracts and Al Casey and Ron Young recommend
Rhom-Air retracts.

Then there is a general discussion of weight with no real numbers.

Tom convinced us (with no rebuttals) that Goldberg, IM, Royal
and MK were not up to the level of B&D.  

See notes 216.* and this one for details.  

Lately several vendors have been advertising struts!

And then Randy Oswald today (see note 1022.21) said he is getting 
Spring Air retracts from Sheldons.

So - Randy - Why did you choose Spring Air?

Do any of the Retract manufactures now sell spring or oil filled
struts with their units?  Price?

Last but not least - anybody know what these things actually weigh?

If individual retract owners or those with detailed vendor specifications
could enter them in to this note then after we gather some data we could
compare.  

Here's the best bet yet - anybody have a set of retracts that they
could bring to the next DECRCM meeting and we could take a close
look at them and talk about their advantages and disadvantages.

Tom - could you bring some B$D?
Eric - you must have something for your pattern planes?
Randy - are you in the Mass area to bring in the Spring Air?
Kevin Ladd - I know for a fact that you have some non installed
90 degree rotating retracts for a Corsair and perhaps some extra
Jug retracts that we could look at.

Soooooo If any of you guys can bring them to the next DECRCM show and
tell meeting - please reply to this note so that we all know who is
coming with what.  Next meeting is 10-Oct-1989.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

My only retract experience was with a Dave Platt Spitfire that I put a Carl
Goldberg set of rettacts in. That was 15 years ago though...

They were mechanical and made mostly of nylon. They had their own retract servo
and power supply that was activated by a micro switch. I liked the idea since it
didn't rob power from the flight pack if the servo stalled. You were supposed to 
have them actuated from the limits on the throttle but I remember seeing others
retract on run up on the ground so I used a separate servo to actuate the switch.
At 11.5 lbs. I wasn't too worried about another ounce or so.

Does CG even make their system anymore? Rhom-airs had just come out but were way
too expensive for my high school budget. I think I paid $20 for the pair of
mains...

Kay,

I am in Colorado Springs. While I'd love to attend your meeting its just too
big a drive. I'll bring in the data sheet on the retracts tomorrow and give you
weights, etc. In fact, if you'd like I'll copy the data sheet and send it to you.
(If more people back east want it I'll let Kay distribute it at one of the
club meetings.


As to why I chose them its pretty simple. The return to down and locked is
spring driven. So, in the event of any pressure system failure the gear
comes down and locks under its own power. Its kind of a feel-good thing. Also,
several of the folks at the field fly them a recommend them highly. Because
of the spring driven return there's only 1 pressure line to each unit, and the
valve is a single  pressurize/bleed toggle, no slide valves and it can be driven
by a microservo. So, all in all it is a very simple system. This is my first
scale ship and I don't like the idea of removing the chin and belly scoops
due to retract failure so the automatic mechanical failsafe really appeals to
me.

Randy

    Kay there are a few new retracts on the market. The one that comes
    to mind is the Prettner retract. Small light and works of the sliding
    block idea that B & D work on.  I have two or three sets on B &
    D's. If I get a chance I'll send ya a set for the meeting.
    
    The B & D is not the lightest retract on the market. It is however
    what I consider the most duriable. We fly off of grass and I have
    never seen a B & D come apart or fail. Most/All other retracts are
    assembled with screws. Their frames being made from metal sheet
    goods. The B & D's frame is machined out of a solid casting of delron.
    THe look somewhat crude at first glance but work slick.
    
    
    Tom

There is a new retract on the market by Robart that is excellent. It can be 
actuated by a standard servo, however I would use a separate 250ma battery pack 
on that servo.

The only downer is it is a light weight retract and suitable for models up to 
about 5 lb.

John

    Kay,
    	I picked up a pair of the new Robart retracts for 40 sized planes
    and I'll bring them to the next meeting.  They look nice but not heavy
    duty.  Bill Lewis plans to use a set in his Bonanza.  They work with a
    standard servo.
    
    Charlie
    

    kay,
    i'll try to remember to bring retracts to next decrcm meeting.
    yes i have a pair of rhom air 90 degree rotating, plus a pair
    of robart mechanical 90 rotating.  to me they look equally
    robust, but the rhom-airs have this drag link that sticks out
    of the wheel well.  i think a byrons 7 second servo powering
    them (robart) would look great, nice and slow and i bet smooth.

OK - I fear that I have narrowed the field to one - perhaps due to my
ignorance.  Does anybody besides Spring Air make an 85 degree retract?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay,
    
    Rhom-air will suit as they have no up-locks and are merely held up
    (wherever they stop) by air-pressure.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

I was paging thru the Tower catalog this weekend and was looking at 
retracts. I got to wondering exactly how the servo controls the airflow 
and noticed that both Rhom and Robart carry a 4-way valve under the replacement
parts. This seemed to be the only control element either of them listed. The 
picture shows a cylinder with 5 taps coming off of it and a control rod running 
down thru the center of it that hooks up to the servo. How's this 4-way valve
get hooked up?

    Dan,
    
    The 4-way valve is the heart of the pneumatic retract system.  Without
    it, the necessary switching (you could liken it to the reversing of
    polarity to a DC motor) could not be accomplished.
    
    Quite simply, at one end of the inner slide's throw, the air lines to
    one side, let's say the "down" side, of the cylinders in the retract units 
    themselves are opened to the air supply while the "up" side lines are
    opened to atmosphere.  This allows pressurized air from the tank to flow to
    the gear cylinders and push the pistons in the "down" direction while air 
    on the opposite side of the piston (the "up" side) is exhausted through
    the valve to atmosphere.
    
    Moving the slide to the other end of its throw causes exactly the
    opposite to occur, i.e. now the "up" side of the system is open to the
    air supply and the "down" side is opened to atmosphere.
    
    Make sense?  It's really tougher to describe than it really is...it's
    deucedly simple once you understand it.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

	I was looking through the latest Tower Talk and there are two 
different Mechanical retracts in there. One was around 18.00 per pair of
mains and the other was 35.00 per pair of mains. Does anyone know
the difference between these ( other than the price ) ?

				Larry

    A couple of brand names would help here?!.
      

    
    	Just planning the latest project, a 1/5 scale Sea Fury.  The Plans
    arrived the other day, and presently I'm assembling the Bill of
    Materials.  All of this aside, the plans are from Roy Vailancourt, and
    the retract gear that has been more or less recommended are HANK LIKES
    units.  This is a line that I have not heard mentioned before, or have
    seen advertised in any of the usual mags.  I intend to pick up a copy
    of the latest buyers guide and check to see if I can obtain an address.
    Another route, will be to contact the plans manufacturer, which I will
    likely end up doing.  However, I was wondering if anyone out there has
    heard of or used this type of retract gear.
    
    
    Regards
    Rod

They might make a scale unit specific to that plane. Is there anything unusual
in the mechanism? Rotation or >90 degree movement?

If not, I'd probably go with one of the more popular units so there's parts
available and easy access.

      I've never used any of his gear, but there are people in my club and
    others at flyin's that I have talked to that have used them. Their
    opinion was not good. Common thread was that they wouldn't or couldn't 
    support the weight they were rated for, and always had a tendancy to
    fold up (Takeoff and landing). Saw some of this personnelly. 
      
      I thought I saw mention a little while back that he had some new gear
    design out, maybe improved, I don't know. I also think that his are 
    strictly electric, and somewhat expensive. 

    Thanks for the replies.
    
    
    	As far as using a substitute, my thoughts are to go with one of the
    air powered units.  Has anyone had any experience with the popular
    brands that can support 30 lb + aircraft?
    
    
    Regards
    Rod

>              <<< Note 216.39 by CGOOA::MALONE "Always Obtuse" >>>
>                           -< Hank Likes retracts? >-
>
>    
>    	Just planning the latest project, a 1/5 scale Sea Fury.  The Plans
>    arrived the other day, and presently I'm assembling the Bill of
>    Materials.  All of this aside, the plans are from Roy Vailancourt, and
>    the retract gear that has been more or less recommended are HANK LIKES
>    units.  This is a line that I have not heard mentioned before, or have
>    seen advertised in any of the usual mags.  I intend to pick up a copy
>    of the latest buyers guide and check to see if I can obtain an address.
>    Another route, will be to contact the plans manufacturer, which I will
>    likely end up doing.  However, I was wondering if anyone out there has
>    heard of or used this type of retract gear.
>    
>    
>    Regards
>    Rod

Rod - if your really going to build the Sea Fury here's what I suggest.
Call Roy Vailancourt up and ask him to bring parts for the Fury and the
retracts to the WRAM show.  Then go yourself and you can look it over.
Roy is well known for excellant plans and when he also sells the wood
parts they are usually of high quality - in other words you won't save
any money or time or quality if you scratch build.

If Roy recommends Kank Likes units then I believe they are good.
But... I have never seen Roy make a harsh landing!

Tell him I said "Hi".

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Sure wish I could get to the show, but I live in Calgary, Alberta, and
    getting the time and money necessary to see the show might be a tough
    one to get by the finance department.  However, I agree with you, and
    will contact Roy by mail requesting information on the Hank Likes
    retract units.
    
    
    Regards
    Rod

    Ok...last night I glued in my retract mounting rails with 12 minute
    epoxy.  Now I must consult your collective wisdom. 
    1) How do I cut the strut down to size on B&D retracts?  I tried using
    a hack-saw, but that metal is like hardened tool steel or something. 
    The saw barely blemished the surface.
    2) How do I connect the servo to the retract.  It seems that the push
    rod has to go under the wheel then way up to the servo.  Alot of
    bending seems to be involved.  Is this correct?
    3) Is there anything else I should be aware of?
    
    Thanks,
    Andy
    

> <<< Note 216.45 by AD::BARBER "And then one day, ten years got behind you." >>>
>                          -< Installation questions. >-
>
>    Ok...last night I glued in my retract mounting rails with 12 minute
>    epoxy.  Now I must consult your collective wisdom. 
>    1) How do I cut the strut down to size on B&D retracts?  I tried using
>    a hack-saw, but that metal is like hardened tool steel or something. 
>    The saw barely blemished the surface.

Dremel cut off wheels.  If you don't yet have a Dremel moto-tool - now
it the time.  You will wonder how you ever got along with out one.

...
>    3) Is there anything else I should be aware of?

Retracts and grass don't mix.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    'Retracts and grass don't mix.'

    But it's really just a straight shot from the retract to the servo.
    
    With the wing in it's normal position, (wheels on the bottom), you
    are going to mount the retract servo in the top of the wing. You
    will probably end up cutting the servo hole clear through to the
    bottom sheeting. Mount the servo so that the servo wheel/arm is just
    below the top sheeting. Cut a hole through each side of the servo
    cut out into each wheel well. The hole should start just under the
    sheeting in the servo cutout, and exit at the "top" of the wheel
    well (keeping in mind that the wing is in it's normal position"
    In other words, if you turn the wing over so that the wheels are
    facing up, the pushrod hole would exit into the "bottom" of the
    wheel well. There may be a couple of minor bends, but not much.
    
    Easy right??????????????????  8^) Don't the plans show optional
    retract installation?????????
    
    BTW.....pay no attention to those persons behind the curtain saying
            retracts and grass don't mix. We fly 99% of out pattern
            contests from grass fields and don't have retract problems.

    Well, good thing that I will probably have to cut through all the way
    to the bottom sheeting because I already have.  I don't know what I was
    thinking, but I was trying to install the servo in upside down. 
    Sometimes those plans really screw me up because half the time the top
    is the bottom and the bottom is the top.  I also can't figure out how
    to mount the retract servo.  There is really nothing to mount it to.
    
    BTW-I wasn't too worried about the grass thing.  I've seen you guys do
    it enough without problems.
    
    andy
    

    ....Finally received an answer from Likes Line on the retract units for
    my Sea Fury.
    
    .
    
        .
    
    
             .
    
    
    
                   .
    
    
    ....Holy *$3# Batman....I just wanted to buy a set of retracts, not
    controlling interest in his company.
    
    
    ... The units are all machined aluminum and stainless steel, with an
    electric gear drive (jackshaft)  Look nice but..
    
    Rough figuring  Retract units ..2 main and 1 tail ...~500.00 U.S
    					Main Wheels........80.00 U.S
    
    By the time I figure in shipping/Handling...customs payoff and convert
    to Canadian, that's like a zillion dollars. Looks like I'm goin air
    powered...might look at adopting a set of the recent AT-6 units from
    Robart (I seem to recollect they are in the $200.00 range, and
    available through the local H.S.)
                                                                     
    Rod (Still suffering Sticker Shock!)

    Does anyone have informations on Robarth retract gears? I am looking
    for one for my 1:6 scale F4U Corsair. The Corsair is scrath build - no
    kit - approx. 20lb. I need to know what types they have (order No.) and
    also the dimensions of the gears to see if they will fit.
    Any info is helpful
    
    regards
    Joerg

There is no "h" in the name. Robart. They are sold through Tower Hobbies and
have a good selection of 1:6, 1:5, and 1:4 scale retracts. Their contact
information should be available in the manufacturers topic (14 or 15).
Corsairs require special considerations for rotation and such so you need to
find someone that makes a specific one for the size you're building. 20 pounds
for 1/6 scale seems heavy (scale weight?? 8^)

    Jim,
    thanks for the info. I think I have a Tower ad in the RC Modelers mag.
    
    20 pounds for a 82" WWII bird is not realy light, I try to do as much
    as possible in CFK, but the ST G4500, gears and (Dubro) wheels add a
    lot of weight. ( may be the bird flies better if I convert the weight
    back from lb to KG :-))))
    
    joerg
    

20 pounds for an 82" bird sounds a lot better. My 1/6 scale Spitfire wasn't
that large so the 1:6 scale reference concerned me.

If you have an RCM, there's probably a Robart ad in there as well. They also
make a Wing incidence meter that they advertise pretty heavily. Same company.

Jim

    Yesterday I talked to Tom Walker from Robart. They have currently no
    landing gears for the 1/6, only in 1/8 or 1/5, but they plan to bring
    out one probably end of next year. They are looking for a kit
    manufacturer who offers a 1/6 Corsair where they can design the gears
    for. Making a prototype for me would cost about $2500.....
    
    
    					may be I sell mine as a kit  :-)))
    
    joerg

    Call Century Jet Models and ask for Gar.  He runs the place.
    
    I have worked with them and developed a set of gear for another
    manufactures A-10 Warthog.  They made them to my specs for the price of
    a regular set.  They are very flexible in this regard and advertise
    that fact.  They will ask you for the critical measurements such as
    strut length from pivot to axle center, strut diameter, axle diameter,
    offset - straight - forked, 90 degree, rotating and so on...
    
    They turned my set around in less than 2 weeks.   Standard orders are
    shipped within a few days.
    
    Mention Chris Spohr from Radio Control Technologies (my side business)
    when you talk to Gar.
    
    Good Luck,