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Popup mechanism works!

November 26th, 2008

I finally settled on a rope and pulley mechanism for raising the roof.    At each corner, I have 1.5″ stainless tube that runs in linear guides.

The guides are also stainless with UHMW bearing surfaces which were turned on the lathe.  

Here’s the forward passenger side guide with the sliding pole.

Routing the ropes was somewhat tricky, but in the end, I got a route that wasn’t too intrusive and involved a minimal number of pulleys.

The ropes are led to a Thern 472 winch.     This is a worm drive winch, which has the useful property of not being driven backwards by the output load.    Thus it acts as a sort of brake to prevent the roof from dropping.   It’s not robust enough to be the only means to lock the roof in the up position, but it does make raising and lowering a pleasant affair.   I’ll most likely use four pull toggle clamps to do that.

In this photo, the winch is clamped to a table in Trog for some prototyping.

I removed the existing input crank arm and hub and replaced it with a 3/4″ lug nut.   It’s the same size as the lug nuts on the wheels, so I can potentially use the same tool to raise/lower the roof and change the tires.

Boring out the lug nut to the 5/8″ diameter of the winch input shaft.

and mounted on the winch.   I’ll use a cordless drill to raise and lower the roof (if it can develop enough torque.   I calculated it to be ~20 in-lbs, which a drill should handle).   Otherwise, it’s 120 cranks to raise the roof!

The winch is mounted with the lug nut exiting on the side, at about waist level for easy cranking if necessary.

And here is the four corner poles raised.  I put about 100 lbs of weight, about 1/3 the roof weight, on the driver side poles — everything seemed ok.   Raising the roof was relatively easy.

I’ve been stressing about this mechanism for quite a while.   It’s good to demonstrate that it should work well.    Now I need to get a few friends in the shop to help lift the roof back on.

Here’s the spreadsheet I used to calc the loads on the winch.

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