Archive for November, 2008

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.



November 11th, 2008

This is an old post that has sat as a draft for quite a while.   I’m finally publishing it…

A while back, I purchased a Precision Temp TwinTemp Jr propane hydronic water heater.   This unit will provide  both hot water for showers as well as heat via a heat exchanger.     It’s a bit big for Trog (it really is designed for the RV market), so I had to get creative in mounting it.

I fabricated this box to into the hole on the right side of Trog.   It will descent about 7″ below the floor, to the same level as the bottom of the frame members.

Note the red primered steel that makes up the “step up” to the rear area.   This, is a heavy  4″x2″x1/4″ gauge U channel piece, which I believe is unique to the firefighters.   The water tank must have added quite a bit of load.     Colby’s Volvo just has some sheet metal here.   There’s some empty space there which makes a useful conduit for water, propane hose and electrical runs.    I left the space uncovered on the right and left edges.

A settee will go above the heater.    This means the right front door will no longer be an entrance to Trog.   Instead, I’m going to use it as a hatch for storage below the settee.


Roof insulation and stiffening

November 11th, 2008

The roof, when removed from Trog is suffers from a fair amount of twist.    That could cause the vertical poptop supports to bind.   To fix that, I have cut a piece of 0.050 aluminum which sandwiches some foam insulation.   That should stiffen the roof up considerably.    I haven’t glued the panel down yet because I still need to layout the interior lighting and run wires thru channels routed in the foam.

I’m gluing the panel to the foam to isolate it from the metal of the roof to minimize thermal conduction.   If I didn’t do this, water vapor from cooking and our breath would condense on the cold aluminum and drip.

Here’s another shot of the roof, with Colby’s TGB11 in the foreground.   He’s subletting space in the shop for a bit to work on his popup roof.