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  #1  
Old 05-26-2013, 08:46 PM
longez360 longez360 is offline
 
Join Date: Sep 2007
Location: Australia
Posts: 23
Default RV-4 Main gear angle

Hi all,

I am trying to ascertain the angle that the main gear leg sweeps back on an RV4. This angle would be that which an extended line from the main gear intersects the top longeron in a free state (side view).

I am also trying to ascertain the angle of the gear leg from the vertical (track, front view).

I would very much appreciate any assistance.

Cheers

Wayne
AUSTRALIA
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  #2  
Old 05-27-2013, 06:21 AM
Les Boatright Les Boatright is offline
 
Join Date: Jan 2005
Location: Titusville, Florida
Posts: 23
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Hi Wayne,
I looked at my set of plans, and from what I can tell, it looks like the sweep-back angle is about 27 degrees. This is the angle that the extended gear leg would make with the vertical plane of the firewall.

As an item of interest, from the side-views in the engine mount drawing (DWG #33), the centerlines of the gear legs appear to be parallel to the angled footwell of the firewall. From DWG #22 for the F-401 firewall, I measured that angle to be around 26-27 degrees. Of course build variation in the firewall applies.

So, a couple of caveats here. YOUR airplane may be different. There could be some +/- variation on this angle . . . depending on the build of the firewall, the firewall alignment with the fuselage, the build of YOUR specific engine mount, and the potential use of any shimming between the engine mount and the firewall.

Also , I know you specifically asked about the angle with the top longeron. But I gave you the angle to the firewall instead because the top longeron is not straight & level for the full length of the fuselage. It makes a bend at the F-404 bulkhead (main spar carry-thru), so the longeron is pitched downward slightly between F-404 & firewall. If you built the airplane, you already know this, so please forgive me for telling you what you already know. However, if you bought it, you might not be aware of the bend in top longeron.

As for the front view (looking aft at the firewall, Drawing #33), it looks like the angle that the gear leg makes with the vertical is about 42 degrees. Again, YOUR plane may be slightly different. And this is the NO-WEIGHT-ON-WHEELS angle as taken from the plans I have, which are circa 1995. I do not know if the gear angles are different for the short-gear versions of the earlier RV-4s (mine has the tall gear). The sweep-back angle should be same regardless, but the outward angle may be slightly different in order to keep the wheel spacing the same on both short & long gear versions.

Best Regards!
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Les Boatright
RV-4 Finishing Kit, S/N 4030
Titusville, FL
EAA 866 "Smilin Jack" Chapter
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  #3  
Old 05-27-2013, 04:49 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Another factor is there is a shorter leg and a longer leg version of the engine mount / gear legs. I don't know the specific angles off hand, but I don't think they are both the same.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #4  
Old 05-27-2013, 05:23 PM
longez360 longez360 is offline
 
Join Date: Sep 2007
Location: Australia
Posts: 23
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Quote:
Originally Posted by Les Boatright View Post
Hi Wayne,
I looked at my set of plans, and from what I can tell, it looks like the sweep-back angle is about 27 degrees. This is the angle that the extended gear leg would make with the vertical plane of the firewall.

As an item of interest, from the side-views in the engine mount drawing (DWG #33), the centerlines of the gear legs appear to be parallel to the angled footwell of the firewall. From DWG #22 for the F-401 firewall, I measured that angle to be around 26-27 degrees. Of course build variation in the firewall applies.

So, a couple of caveats here. YOUR airplane may be different. There could be some +/- variation on this angle . . . depending on the build of the firewall, the firewall alignment with the fuselage, the build of YOUR specific engine mount, and the potential use of any shimming between the engine mount and the firewall.

Also , I know you specifically asked about the angle with the top longeron. But I gave you the angle to the firewall instead because the top longeron is not straight & level for the full length of the fuselage. It makes a bend at the F-404 bulkhead (main spar carry-thru), so the longeron is pitched downward slightly between F-404 & firewall. If you built the airplane, you already know this, so please forgive me for telling you what you already know. However, if you bought it, you might not be aware of the bend in top longeron.

As for the front view (looking aft at the firewall, Drawing #33), it looks like the angle that the gear leg makes with the vertical is about 42 degrees. Again, YOUR plane may be slightly different. And this is the NO-WEIGHT-ON-WHEELS angle as taken from the plans I have, which are circa 1995. I do not know if the gear angles are different for the short-gear versions of the earlier RV-4s (mine has the tall gear). The sweep-back angle should be same regardless, but the outward angle may be slightly different in order to keep the wheel spacing the same on both short & long gear versions.

Best Regards!
Thanks Les. Much appreciated.
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  #5  
Old 05-27-2013, 05:24 PM
longez360 longez360 is offline
 
Join Date: Sep 2007
Location: Australia
Posts: 23
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Quote:
Originally Posted by rvbuilder2002 View Post
Another factor is there is a shorter leg and a longer leg version of the engine mount / gear legs. I don't know the specific angles off hand, but I don't think they are both the same.
Thanks. Valuable information also.
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