Tailwheel steering spring strengths

cardiffrob · Post by **cardiffrob** » Sun Apr 20, 2008 8:37 am

Is there any science involved in selecting spring strength? The steering gear that came with my 'project' didn't have any springs on the cables so I bought some springs from Halfords to do the job. Too strong and they'd put strain on the rudder hinges and operating arms. Too soft and....what?

I've weighed the tailwheel and assembly and it is less than the skid that currently hangs there (by a few ounces)

Rob Swain · Post by **Rob Swain** » Thu Apr 24, 2008 12:03 pm

No science but...

Maule tailwheel springs are of different strengths / sizes to help avoid shimmy. I believe there is some debate as to their efficacy in that regard.

They are also compression springs so, I'm lead to believe, if they snap or get weak you don't lose the tailwheel steering altogether like a spring in tension would. I have seen springs in tension used though, so maybe this is less important than it may at first seem.

As I understand it tailwheel cables / chains should never be so tight as to apply pressure to the rudder horns, hinges when "the system is at rest" (for want of a better term). Bad for the rudder hinges and bad for the tailwheel swivel spindle.

Phil Burgess · Post by **Phil Burgess** » Thu Apr 24, 2008 5:51 pm

The maul springs are quite large and heavy, though very similar compression type springs can be found in many car exhaust systems. These may be better suited to smaller lighter homebuilt types. I've found the maul unit and springs as fitted to my pitts a bit tricky to set up and keep working well. Too slack and theres no steering until the rudder gets to full travel; too tight and the swivel will not break out for tight turns. This is just a reflection on the poor geometry of the pitts design rather than the maul unit which is excellent and stands up well to the hammering that most of my landings send it's way!

Tony Harrison-Smith · Post by **Tony Harrison-Smith** » Thu Apr 24, 2008 6:41 pm

Sky-craft sell the springs used on the Rans taildragger, if that is any help. they are at http://www.sky-craft.co.uk/acatalog/Rans_Spares.html
and then search for 'Tail Wheel Springs TW-S-SPR'

Tony

mikehallam · Post by **mikehallam** » Mon Apr 28, 2008 5:46 pm

I experimented with different springs till satisfied with the compromise on the S4. The construction book pic actually shows fixed links ! As bought 4 yrs ago they were quite strong coil springs, so almost fixed. Real trouble with the simple non break free swivel was that if turning the a/c say towards 90 degrees the wheel tried to swivel but the d**d springs really loaded up the poor rudder stops. Softer springs with a length of wire loop to soften more, work well as the loading when turning is much reduced, naturally the brakes then need to be used more when taxying in any cross wind as it doesn't hold straight so easily on tail wheel alone. However on the landing it permit plenty of steerring & that's what counts for me.
BTW the tail wheel springs are removed completely to hang free on those few times you have to leave the a/c for some moron to push around as beyond 90 degrees, such as mindless pushing backwards, will tear the poor things out by the roots - another reason for soft springs. They can die cheaply without wrecking the fuse fittings when you get it moved without permission by some helpful bystander, even if he is a pilot too.

cardiffrob · Post by **cardiffrob** » Thu May 01, 2008 7:28 pm

Do the springs HAVE to have full loops at the ends to keep them from unhooking? I've not found 'simple' springs with fully coiled ends.

mikehallam · Post by **mikehallam** » Thu May 01, 2008 10:42 pm

Yes,
However with snipe nose pliers one can readily do that. [Unless the spring a really thick wire].