Die Sring Gear
Hi Glen,
Die spring gear works well, I have it on my Northstar. However be carefull of the design. Mine broke, but it was because of a combination of design and a lot of hard off airport landings.
My die springs are a 2" dia.spring 12" long. Theoretically they can support 1700 pounds each. My plane weighs 1260 Lbs. empty which is probably more than most cubs.
Anyway when you add a couple of guys some fuel etc. and it is often at about 1800 ( gross is 2450).
You have to preload the springs roughly equal to half the weight you want to carry. If you don't the gear will splay out as soon as you put the plane on it.
In my case this means a preload of about 1 1/2" , . The problem is a 12" spring only has a travel of 3.5" before preload.
When you clobber it hard two things happen for sure, and maybe more that no-one will ever understand.
The springs bottom and the energy goes into the airframe, causing it to be hard to grease it on.
The energy can also be destructive, my struts broke between the spring and the axle. I fixed the problem by increasing the thickness of the strut tubes and making some changes to the strut design.
I made a Cadd drawing of the strut I made and will share it.
You can find listings of die springs and the pressure they will support at various web sites. Anchor Lamina have a site where you can download a chart.
In the near future I plan to study the use of urethane rubber in place of the die springs, with the intention of getting more travel without bottoming the suspension.
Let me know if you want that drawing