[fretman_2]

It's a MDF gantry and I thought about something like this...



...but I want to make sure that the gantry sides are nice and secure. It's two pieces of MDF on top of the truck and the gantry sides are screwed to that.

Tnx,

[louieatienza]

I'm not the biggest fan of that method because you're relying on the strength of the joint of the MDF to the side, which is a weak point. Plus you're screwing into the weakest part of MDF, the middle. Think of MDF like a torsion box of sorts, the outer layers are the hardest densest parts, and the middle merely creates the thickness and not too much more. Some folks mount the block on its side which is OK but provides about 70% the load rating of the block. This is likely fine in your instance since the MDF is considerably light compared to the load rating of the block.

[louieatienza]

BTW they do make SBR trucks with side mount holes, though they're not as easy to find. You could ask your supplier if he can source them for you. Another way would be to get flanged blocks, then you would have to mount a foot to your gantry legs to mount them.

[fretman_2]

Thanks Louie...I wonder if hardwood would work instead of the two pieces of MDF?? If not, I could look at side mounting the rails.

[louieatienza]

Thanks Louie...I wonder if hardwood would work instead of the two pieces of MDF?? If not, I could look at side mounting the rails.

If I were to choose hardwood, I'd use either something like mahogany, which is very dimensionally stable.

[ger21]

I just can't picture what I'm looking at...

[louieatienza]

I just can't picture what I'm looking at...

If you get this card in Pictionary, the answer is Gantry!

The circle within the rectangle represents the sectional view of the SBR block sans support rail. To the right is a gantry upright, of doubled MDF.

The question was whether two small MDF blocks, glued face to face, and glued and screwed to the gantry side would suffice for supporting the gantry's weight and machining forces (since he wants the SBR rail/block in the upright position) and the SBR mounting holes are on the top of the block.

[fretman_2]

I may be able to shake up some mahogany...I have some Sapele.

[jcarpenter2]

I wouldn't build a gantry out of wood/mdf, but if I were to I would use proven joiner technics, like a sliding dovetail or a mortise and tenon plus a high grade glue. Butting two pieces of wood together end to end and relying on screws/bolts for the stability is never a good idea in my opinion.

[wizard]

I must be missing something here but why not bolt the bearing block to the side of the upright?

Also is this for unsupported rails? If so you won't loose as much in capacity by this arrangement. The unsupported rail is an issue all on its own. Generally take the simplest arrangement of components you can. Complexity generally weakens a design, if I understand your drawing what you are doing is cantelevering a mounting block off the side of the upright.

Can you make something like this work certainly but it will make for a more complex build, with more components that need to be aligned nearly perfectly. Of course if I'm not understanding your drawing correctly then all bets are off. I would ask myself you would I get all the pieces square and parallel.

[louieatienza]

I must be missing something here but why not bolt the bearing block to the side of the upright?

Also is this for unsupported rails? If so you won't loose as much in capacity by this arrangement. The unsupported rail is an issue all on its own. Generally take the simplest arrangement of components you can. Complexity generally weakens a design, if I understand your drawing what you are doing is cantelevering a mounting block off the side of the upright.

Can you make something like this work certainly but it will make for a more complex build, with more components that need to be aligned nearly perfectly. Of course if I'm not understanding your drawing correctly then all bets are off. I would ask myself you would I get all the pieces square and parallel.

Not unsupported rails, it's just a rough sketch.

[Louis_Cannell]

Why not use lengths of Angle 2x2x1/4" aluminium or 1/8" steel just drill bolt to mount and to side.

[fretman_2]

I'm sorry guys...yes...it's supported rail. I just didn't draw in all of the support. Louis...thank you. I just didn't think about using angle aluminum or steel. I had a duh moment for sure.