Torsion Lift Assist Hinge (For Custom Built Flippac Truck Shell)

[kozaz]

I'm thinking of building a custom flip top from a truck camper shell. (Kind of like the Flippac or Wildernest)

I was wondering if anybody had any sources for a "torsion tube like" hinge set up. Or any ideas on what else could be used in it's place? (Besides an electric winch and a jungle gym of tubing)

It would be kind of heavy, so some sort of lift assistance built into the hinge would be helpful. Also, maybe it would be nice to build something to keep it from slamming shut as well?

This is just a planning stage, trying to get some ideas, to see if it's worth the trouble.

Thanks,
Ryan

 

[ntsqd]

The Flip-pac hinge is it's torsion bar. From working on the one that Red87 has/had I learned that the neutral point (zero spring load) was with the lid straight up. It helped you lift in either direction and it helped keep it from slamming in either direction. Reversing torsion is just about the worst possible thing that you can ask of spring steel.

The later toyhaulers use a wound torsion spring at the hinges instead of the garage door spring/drum/cable system of older models. Those that I've seen employ several of them, so one is not strong enough for those rear doors which might mean that one or tow would be all that you would need should you opt to go that direction.

 

[JimQPublic]

Kozaz,

Did you get anywhere with your quest? I'm thinking the same thing, but on a trailer. The spring assist seems the trickiest part.

I have a Chalet brand folding trailer that has coiled torsion springs to assist in raising the roof, but I'm not sure if they would work in the opposite direction. (not sure where the 0 point is). A little research tells me that torsion springs can be used in both the "coiling" and "uncoiling" directions, but uncoiling there is some reduction in performance and loss of stability as the mandrel gets loose.

My plan has a 80" x 60" bed platform (1/8" plywood skins over xps polystyrene core, 4 oz. glass cloth, epoxy, & paint for 1.2 to 1.5 pounds per square foot on average), and 4" foam mattress (about 20 lb). Add the tent and total weight is approaching 80 pounds. The center of mass is 40" from the hinge, so when horizontal it would take 267 ft*lbs to lift? It looks like the Flippac uses a 18" or so handle and maybe 40 pounds of pull? That still means the springs have to offer a combined 200+ ft*lbs of torque at 90 degrees deflection.

This may be a deal killer. Looking online most torsion springs seem to be rated much lower. I think Flippac's design using a long torsion bar with splined ends is brilliant- but may be hard for the home builder to replicate. Wonder if they ask any questions when you order a new torsion bar, hinge arms, and assorted hardware?

Expedition Portal thread with great photos of the torsion bar setup.

 

[ExpoMike]

My thought would be to use a splined "sway bar" setup like they use on sprint car and other race car applicatons. They offer many rates and splined arms and mounts. I am sure something could be fabbed up, after looking at that above link and seeing what Flip-Pac is doing.

Hope that helps some.