Eagler's Nest

General Category => Off Topics and General Interest => Topic started by: rfeenstra on January 15, 2014, 08:01:49 AM

Title: Tail wheel Caster
Post by: rfeenstra on January 15, 2014, 08:01:49 AM

There is an interesting article in the latest Sport Aviation on tail wheel caster.  It shows that proper tail wheel geometry is to have the top of the pivot bolt farther aft than the bottom giving a positive caster. As the tail wheel is loaded, caster would move toward 0 degrees.  This is the opposite of what I always thought and what I thought the DE plans showed. Did I misinterpret the drawing? Leonard calls for 2 degrees positive caster but appears to define positive caster as the opposite of what the article says.  Do I need to change my tail wheel geometry?

Rob

Title: Re: Tail wheel Caster
Post by: rfeenstra on January 15, 2014, 08:26:29 AM

I found this article that seems to be the basis of the Sport Aviation article: http://www.backcountrypilot.org/forum/interesting-article-on-tailwheel-shimmy-687 (http://www.backcountrypilot.org/forum/interesting-article-on-tailwheel-shimmy-687)

I think I need to do some spring bending!

Title: Re: Tail wheel Caster
Post by: rockiedog2 on January 15, 2014, 02:21:15 PM

i've always built mine with the bottom of the pivot bolt trailing the top and have never had a problem with shimmy. i saw the article and thought same as you...opposite what i had always done. on this new one i built it same as always have. i'm not changing anything til test it first and see what i got.

Title: Re: Tail wheel Caster
Post by: Sam Buchanan on January 15, 2014, 08:05:22 PM

Here is the tailwheel setup on my XL:

(https://www.eaglersnest.com/forum/proxy.php?request=http%3A%2F%2Fhome.hiwaay.net%2F%7Esbuc%2FlegaleagleXL%2Fcontrols-11.jpg&hash=5b83b56d020797e3b1bddf244f787e7a20b84705)

It has proven to be flawless in operation. The tailwheel has less castor when resting on the ground but the top of the pivot is definitely forward of the bottom.

Title: Re: Tail wheel Caster
Post by: rfeenstra on January 15, 2014, 08:58:37 PM

Perhaps because your wheel trails so far behind the pivot point, it negates the potential problem of a negative caster angle.  I have a worn out Maul that I was going to use, but it is heavy so I'll probably make one or look at Matco.

Title: Re: Tail wheel Caster
Post by: weasel on January 17, 2014, 02:59:47 PM

(https://www.eaglersnest.com/forum/proxy.php?request=http%3A%2F%2Fwww.rehab.research.va.gov%2Fjour%2F00%2F37%2F3%2Fkauz-f04a.gif&hash=560b0802407832899a4710b83b37230cdb42f4dc)