We are building a new roll off building observatory for a large telescope.
The concept was that this would be a quick and dirty, smallest footprint possible and low cost operation.
We`ve had experience in building many others but this would be the first roll off building.
The design started out as a 4`x8` footprint building on wheels running on rails on deckblocks. One entire end would be a double door and the roof would be fixed.
After more design reviews including scaling down the sidewalls from 2×4 studs to 2×3 studs, we thought the margin of clearance for the scope (48″-6″=42″ and the scope was 36+6-1=41″) was less than 1 inch. Too close for comfort. So the footprint was expanded to 5×8 feet.
There is no real soil in the area.. limestone rock covered by a couple of inches of peat moss. Concrete pads are out of the question as this is a temporary installation.
The height of the building needs to be 5 feet taller than the top of the pier.

Project steps in approximate order needed to complete by end of August 2012

1. measure out rails,blocks. outside wheel to outside wheel: 48″-1.5″-1.5″-1″-1″= 43″ should place the wheels on the centre of the rail. Rev2: 60″ outside move 12″ in on each side to balance = 60-12-12=36″ hmm this is worse than before for stable stance. Try 10″ in from the outsides: 60+-20=40 inches . No. Try 6″ in from outside = 60-12=48″ better.

2. lay down gravel and then deck blocks. Revision2 dig down hole as platform floor is now 2+4+5.5+7+1.5+5.5+.75 = 26.25 inches (gravel+deckblock+rail+ wheel+wheelsupport+ platform frame+platform floor) is too high above grade. So that would now be -4 added to the above giving the platform floor 22.25`above grade. Still high and may require a step to get inside the observatory when it is rolled open.

The concept being to unlock building, open doors, roll building off, lock down building, lower trap doors, go inside building, turn on power, start up computer and telescope and work inside the building.

3. place deck blocks
4. place 2x6x8 rails and level deck blocks, measure for parallel
5. attach rails with plates

varathane rails

6. build 4×8 platform frame. Revision2 is now 5`x8`
7. add 3/4 plywood to platform frame. Revision2 – cut plywood to fit
8. cut out gap area for pier
9. mount four wheel supports 2×6 rev2 flat, more support
10. mount four 6 inch wheels with bolts from top, nuts at bottom.
11. Add rail end blocks to stop building from rolling off track.
12. Mount platform and test rolling. Cover with tarp when not in use.
add C channel for wheels to run in or add 1×4 edges along rail to keep on track
13. build side walls using 2×3. double up ends and maybe L mount them. Long walls are a full 8′
14. Build end wall shorter than 4′. It fits inside. Build and mount frame first then add plywood after installed. rev2=5`
15. Build dual door flap cover for floor opening to allow rolling. Rev2 now has 6 inch end walls on the southern doors allowing for full 48 inch doors (2x24in) but with better support and stability.
16. build trap door cover for 15″x18″ opening where pier is when building is opened
17. Roof – metal 4’x8′ with overlap, slightly elevated at one end for drainage. elevated parts to be tricky. Rev2 now 5feetx8feet
18. Doors two 2′ at front, open all the way, hinges on outside. cover gaps with wood and weather stripping. add secure lock
19 misc. check for screened venting to aid cooling
20. Paint outside walls white.
22. add power cable
23. add cable conduit at pier
24. add computer, folddown table, mount lcd display on wall.
25. test operation.
26. oh yes.. install telescope!