Engine mount replacement for the RV 3

[J29racer]

Above all the rest of the stuff going on with the RV 3 I have a separate issue and that is an engine mount repair or replacement. After talking with Van they tell me there are two types Dynafocal and Conical type I have an old O-320 engine and new motor mounts, so I would like to keep those. Does anyone have pictures of the two types and are the bolt alignment to the firewall the same for both of them.

 

[David Paule]

It should be clear when you look at the engine. If the bolt to the engine and the isolators is parallel to the crankshaft, it's conical. If it's angled inward at the foreward end (and pointed down for the upper ones and up for the bottom ones), it's Dynafocal.

But note the there are two types of Dynafocal ones. One is in general use, the other, I think and could be wrong, used n Twin Comanches.

Dave

 

[J29racer]

Well thanks for that the engine mounts are pointed in sort of focusing on a common imaginary point in the center half way up the engine if you know what I mean.

 

[David Paule]

Sure sounds like a Dynafocal to me. Which one, is a question.

Dave

 

[Flyjon57]

Above all the rest of the stuff going on with the RV 3 I have a separate issue and that is an engine mount repair or replacement. After talking with Van they tell me there are two types Dynafocal and Conical type I have an old O-320 engine and new motor mounts, so I would like to keep those. Does anyone have pictures of the two types and are the bolt alignment to the firewall the same for both of them.

The two types of mounts are dynafocal I (one) and dynafocal II (two). The “one” is focused at a point about at the forward end of the crankshaft.
The “two” is focused at a point ahead of the crankshaft forward end allowing for the space of the propeller.
I hope I am describing that right. The engine that I have came from a Twin Comanche and I sent it into Divco for “repair” and remade as conical. The original designation: IO-320 C-1A
It had aft mounted fuel injection with a 45 degree intake adapter to bring air in from the side of the engine nacelle.

 

[pjc]

Above all the rest of the stuff going on with the RV 3 I have a separate issue and that is an engine mount repair or replacement. After talking with Van they tell me there are two types Dynafocal and Conical type I have an old O-320 engine and new motor mounts, so I would like to keep those. Does anyone have pictures of the two types and are the bolt alignment to the firewall the same for both of them.

Drawing 29 of the RV3 plans (attached) shows side views of both the conical (left side of drawing) and dynafocal (I) mounts (right side of the drawing). Both examples in this drawing attach to the firewall at 6 points (as does my RV-3B Dynafocal mount).

There may have been other engine mount designs for some “early” builds (no two RV-3’s are identical!). I know of an (early) RV-3 which had a conical mount with only 4 attachment points at the firewall, but I’ve not personally seen one.

Peter

 

[FinnFlyer]

Drawing 29 of the RV3 plans (attached) shows side views of both the conical (left side of drawing) and dynafocal (I) mounts (right side of the drawing). Both examples in this drawing attach to the firewall at 6 points (as does my RV-3B Dynafocal mount).

There may have been other engine mount designs for some “early” builds (no two RV-3’s are identical!). I know of an (early) RV-3 which had a conical mount with only 4 attachment points at the firewall, but I’ve not personally seen one.

Peter

Yes the two attachment points near top of gear leg sockets was an addition to the original design. Should also include F-312 (angle and web) shown on drawings #20, #24 and #25 but not on drawing #21. I did that on my RV-3A back in '99. Unfortunately the builder of my 2003 RV-3B omitted that (custom engine mount). That modification is nice because it creates a nice area for battery or other things. Basically it transfers gear leg fore-aft movement forces to bottom of main wing spar.

 

[jrs14855]

the odd dynafocal was used only on the Twin Commanche and Wing Derringer. The Twin Commanche's all had special Hartzell props with long built in extension. The different mount angle was to deal with issues created by the long extension. Twin C are either 0 320 B or C and all have aft mounted fuel injection.