Last mod to the Magnum

[RDavidson 183]

I don't know if the original leaf spring on my Magnum got stretched out a little over the years, but when I put my new Matco Tailwheel on it, the angle gave it negative caster which is bad.  It would have shimmied like a shopping cart with the wheel post bent back.

I had purchased a Husky Tailwheel leaf spring and the mounting hardware for another aircraft but didn't use it.  It was pricey, I think $250.  When I got the leaf spring I took it to a leaf spring shop and a guy made me a duplicate for $50, so now I have a spare for cheap!

Anyway, I put it on my Magnum and man did it help raise the tail up and it also gave me a positive caster angle.  It is also a three leaf instead of two which will strengthen it.  The chains will be at a really steep angle, but I've had that before and it worked fine as long as you left them slacked.  If you make the chains tight it will bend the Tailwheel arms upward.

I had to fabricate a bracket that angled down from the tailpost and holds the leaf spring up to keep it from moving side to side.  I couldn't weld it in place because of the fabric being attached all over that piece, so I drilled and tapped two small bolt holes into the leaf spring mount plate.  It seems to work pretty well.  However if you are just starting a Magnum kit you might want to look at doing something like this before you cover the fuselage so you can weld a mount in place.

 

Ron

 

[Barry Cole 111]

Looks Great Ron!!

[RDavidson 183]

Thanks Barry...

Here is a great pic if I lost some of you with the Positive vs Negative castor bit...

 

Edited 11 Nov 2016 by RDavidson

[EDMO 1078]

This is one of the many reasons I don't like tailwheels - My book says that the head of the pivot bolt should be about 5 degrees forward of the bottom of the bolt for the tailwheel to be stabile in forward motion - In other words, the tail should be at its lowest point when the plane is moving forward in a straight line - any deviation from the straight line will cause the tailwheel to raise the plane tail higher.  The proof is in the tracking, handling and lack of shimmy.  

Don't take much to confuse me!  I just put the 3rd wheel on the front for better visibility and leveled parking!   ;<)  EDMO

Edited 11 Nov 2016 by EDMO

[RDavidson 183]

Ed,

I hear you, that is why I posted the above pic...I discovered it myself, with my last plane, that this works.  I have also had a chuckle or two seeing Tailwheels with negative castor and the owners complaining about shimmy.  The next time you go to the grocery store and you have a cart with a wheel wiggling back and forth I'll bet you a cold beverage it is angled to the back (negative).

Ed, have you been hiding from Tailwheels all this time?   Certainly you have flown a few?  Come to the dark side...higher insurance, crosswind limitations, the fear of a chain breaking, the ever looming ground loop...What's not to love about Tailwheels?

Ron