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ACRO E-mail Archive Thread: [Fwd: spring gear]


Thread: [Fwd: spring gear]

Message: [Fwd: spring gear]

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From: Liz Wolf <ewolf at>

Date: Fri, 21 Feb 1997 20:58:05 UTC


  Message-ID: <330E0ACC.2BD5 at>
Date: Fri, 21 Feb 1997 12:51:24 -0800
From: Liz Wolf <ewolf at>
Reply-To: ewolf at
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To: daotero at
Subject: spring gear
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Dear Dave,

Came across your request for putting RV gear on a Pitts S-1. It works
very well. Your pay about a 12 lb. weight penalty, but the performance
of the aircraft goes up. This is due to the fact that it is enough
cleaner that the planes speed is up and you can acheive entry speeds
quicker. The real advantage is that for a spring gear on a Pitts, it
does away with the twisting of the lower longerons you get with a slab
type spring gear. All the loads are on the engine mount, not the
longerons. Also a stock bungee and slab spring gear has a track of
around 53". The rod RV-3 gear legs give you a 64" track. We've put these
gear legs on 4 Pitts S-1's. It gives the feel of landing a Citabria as
far as the roll out and nice shock action. Its real advantage is that
now you get rid of the bungee box on the firewall and you can put a
tunnel for the cooling air. This really helps get rid of cooling drag.
In conjuntion with the gear we use the Delmar Benjamin (Gee Bee Pilot)
cowling. Its got to be the lowest drag cowling around and looks real
good. In the latest IAC magazine, there is a picture of Norm Willis's
Pitts we built for him. This uses everything I talked of. It has an
IO-360 paralell valve that dynoed 239 hp. I have around 30 hours fllying
this plane and at 25" and 2500 rpm., it will indicate 185 mph level
flight at 3000'. We flew it cross country with an Extra 300S and at the
same power settings of 24 squared, the Pitts was just a little faster.
So you can clean up a Pitts and make it go.

The mod the way we do it requires the removal of the bungee stubs in the
fuselage and a fifth point for the mount at the bottom center. Then we
build the mount with the gear sockets on the inside of the lower mount
bushings with diagonal braces going for this bottom point to the lower
lord mount sockets. This keeps the gear from moving for and aft. Then we
run tubes from this point down to the middle fifth point. Also a cross
tube between the gear sockets at top. On the Pitts the gear is futher
forward than an RV-3 and you will need to get the axles in the same
place for and aft as the bungee gear for proper tail weight. Well thats
about it. Have fun.
 Steve Wolf


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