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

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


Thread: [Fwd: spring gear]

Message: Re: [Fwd: spring gear]

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From: Herman Dierks <dierks at>

Date: Sat, 22 Feb 1997 00:16:16 UTC


   Liz, thanks for the informative posting.
 I fly both RV4 and Pitts. 
 One common problem on the RV's that everyone has is a gear leg
 shimmy when slowing down on the landing roll out on pavement.
 This normally happens around 10 to 15 MPH. 
 Some of the RV's (including mine) were modified to add some
 wood strips to the gear leg and wrap them in fiberglass.
 This helps dampen the gear leg oscillations and helps the shimmy.
 Tire pressure is also a factor.
 Others have claimed that balancing the wheel pants with lead 
 to balance about the axel will also help. I have not tried this.

 This is a minor problem but I was wondering if you see the same
 thing on the Pitts with the round Whittman tapered spring gear?

 Also, some of the RV's have had the top of the gear leg socket
 bust out. Van's now welds the doubler ring at the top of the 
 socket all the way around the top instead if just rosette weld it.

 dierks at

> Message-ID: <330E0ACC.2BD5 at>
> Date: Fri, 21 Feb 1997 12:51:24 -0800
> From: Liz Wolf <ewolf at>
> Reply-To: ewolf at
> X-Mailer: Mozilla 3.0 (Win95; U)
> MIME-Version: 1.0
> To: daotero at
> Subject: spring gear
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> 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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