Which rollers for roof of roll off roff obsy

[Gina]

ABS is somewhat elastic so I guess that causes the load to spread a bit.  This has the effect of reducing the pressure but at the same time increasing resistance - just like rubber tyres but less so.

[Mikyg]

Blimey...that's a massive warm room! Are you going to hold parties in there?

What a good idea haha. Its the 250 pds with an neq6 on a 5ft pier. Wanted to make quite a bit of room in there as my dads quite a big fella lol plus that shelf is gonna stick out quite a bit for lenses, camera gear etc.

[Mikyg]

What a good idea haha. Its the 250 pds with an neq6 on a 5ft pier. Wanted to make quite a bit of room in there as my dads quite a big fella lol plus that shelf is gonna stick out quite a bit for lenses, camera gear etc.

The warm room is gonna be 6x8ft

[Zakalwe]

The warm room is gonna be 6x8ft

Thats bigger than my whole obsy! #envious!

[Merlin66]

For the "Plan A +1/2" design - a 3 x 2 m ROR on the existing shed, I used 3 x 95mm rubber wheels on each side running in 100 x50 C section.

This ensures the wheels can't lift....rolls well at the moment...

[Gina]

I like the idea of "anti-liftoff"   As long as any twisting moment doesn'y cause jamming.

More thoughts of my ROR...  I have a 5m length of 1" anodised aluminium tube which I could use with printed wheels which I would expect to work better than V section.  OTOH the roof is usable ATM and I might just wait until I have the funds and update to steel track and wheels later - better done in warmer weather anyway.

[Tinker1947]

You could do away with the shelve in the scope room and put corner shelves up, they don't get in the way and 3 or 4 in each vacant corner won't get bumped it to and will add to the strength if there are battens behind the wall.....

[rwg]

Well... t'would be nice but 4 wheels and 3 lengths of track and 2 joiners come to £144.28 - can't afford that for a month or two   Back to the 3D printer then

When I did mine, FH Brundle were cheapest for the track (about £18 per length, although I can't recall if that was inc VAT or + VAT). The best value wheels came from ebay - £14 each - http://www.ebay.co.uk/itm/80mm-Gate-wheel-pulley-wheel-in-bracket-sliding-gate-heavy-duty-for-20mm-bar-/221237670382?

cheers,

Robin

[Gina]

Thanks Robin   But cheaper and stronger are these wheels from FH Brundle and this is the track

[rwg]

Oooh, they didn't have that pattern when I did mine, and I didn't fancy using the bare 80mm wheels as I wasn't happy that I could sort out mounting them properly.

cheers,

Robin

[Zakalwe]

Go for the largest wheel that you can. Mine are 120mm and the roof is dead easy to move.

[Gina]

I didn't see those cheaper wheels when I looked last.  This would be my costs using those :-

Using the 120mm wheels the cost comes to £144.  Biggest wheels are 140mm OD nearly twice as much as the 120mm and 4 times the 100mm.

I could compromise a bit and use bigger wheels for the heavier south side (with the roll off wall) and smaller ones for the much lighter north side.

[rwg]

Gina,

I have the 80mm wheels and the roof rolls with the push of 1 finger (my observatory is about 8' square). I can't see any real need for the 140mm wheels at 4x the price of the 100mm wheels. Surely 3 wheels per side would be a better option if you want to upgrade the 'beefiness' of the system?

cheers,

Robin

[Lonestar70]

Mikyg,

A 16ft  roof would need a minimum of 3 wheels per side or the centre will sag... unsupported side timbers supporting a roof with plywood and steel roof cladding x 8ft wide will be quite a heavy load and WILL BEND... especially with snow on it.

Nice obsy design though.

Good luck with the build.

Best regards.

Sandy.

[Owmuchonomy]

My new build has a 8' x 19' foot roof with an 8' roll off. The roof weighs in at just under 1 tonne. I have 6 wheels with roller bearings each side on the the same groove as Zakalwe. Don't underestimate the weight. The roof rolls with a couple of finger pressure though.

[Gina]

Gina,

I have the 80mm wheels and the roof rolls with the push of 1 finger (my observatory is about 8' square). I can't see any real need for the 140mm wheels at 4x the price of the 100mm wheels. Surely 3 wheels per side would be a better option if you want to upgrade the 'beefiness' of the system?

cheers,

Robin

My roof is the same size but includes a couple of feet of wall on the south side which adds quite a lot to the weight but I'm sure two wheels would be quite sufficient to carry the weight at 300Kg per wheel.  The north side is quite light and I can lift it myself  

[Gina]

A problem with 3 wheels on a side is getting all three aligned.  If they aren't the friction will increase considerably.  The middle wheel could be arranged to slide sideways perhaps but that's increased complexity.  For a long and heavy roof it might be better to have a flat track and wheels to match with separate wheels to guide sideways at the ends.

[Mikyg]

Thanks for the advice guys, thinking maybe 4 of the gate wheels down each side to be safe,

[Gina]

I'm now considering two options for track and wheels from FH Brundle.  In either case, 3 track lengths cutting one in half to give 4.5m.  2 pins to join the track and 2 of the 100mm wheels for the lighter side.  Then I'm considering either 120mm or 140mm wheels for the heavier side - the difference is £30.  I'm wondering if the difference in size is worth £30.  I know this is my decision but not sure if the larger size wheels would make any noticible difference.

[Gina]

I have rigged up a hoist and digital spring balance to weigh the roof.  Tried lifting the whole of the heavy side from under the apex but it exceeded the 50Kg limit of my scales.  So went for one end and that weighed in at 35Kg.  The ROR carriage was over an inch up at that end and well clear.  At the other end the weight is being taken by one wheel 250mm in from the end of the ROR so I guess I need to add about 10% to my weight measurement.  I estimate the weight of the heavy side of the ROR as around 80Kg.

I'll go and weight the lighter side now...

[Gina]

Total weight of north side of roof is <18Kg.  This is with the roof pushed upwards on the apex beam and all clear of the running rail.

Clearly the 100mm wheels will be more than adequate for this side and with only 40Kg on each of the south side wheels I think the great big 140mm wheels would be overkill   But opinions are always welcome

[Gina]

I did some measuring up too.  The roof actually moves 2.2m between closed and open.  Minimum wheel spacing would be 1.2m.  That gives a minimum track length of 3.4m.  My timber rails are 4.3m long so the track will require two hacksaw cuts - 4.5m is longer than the timbers they will be screwed to.

[rwg]

I used the 3 lengths of track, one cut in half to give a track length of 4.5m approach too. I guess my wheels are about 25-30cm in from the ends of the roof, so 1.6m - 1.8m apart or so.

Didn't bother using the joining pins for the track (when it's screwed onto a 4x2" timber every 18 inches it isn't going anywhere), but I did make sure the  joins were in different places on the two tracks.

cheers,

Robin

[Gina]

I agree that the pins shouldn't be needed.  And with only 40Kg load I think it's a toss-up between 100mm and 120mm wheels for the south side (£16 price difference) - I think the 140mm wheels would just add to the weight

[Gina]

I went for the second option above and the goods arrived this afternoon.  Looking good   The 120mm wheels fit the track perfectly (maybe too perfectly unless I can get the wheel carriers mounted precisely on the ROR carriage but should be alright).   OTOH the 100mm wheels are a bit wider than the track and run on the top - looks like they were meant for a wider profile track, which is strange considering they are on the FH Btundle 300Kg 20mm web page.  I don't think this will be any problem for the lighter north side which currently has no guiding - just rubber tyred wheels on timber track.  Glad I decided on the second option though.