Thread: Workbench Structural Anatomy

Originally Posted by Different

... next bench will be 100mm thick laminated Kwila 3000mm long & 1100mm wide on a Vic Ash frame ....

Hooooollllllleeee Sheyet!!! A diesel mechanic.
Struth Ruth.... what the F' are you building???? :eek:

Mine's made out of Kwila & it's half that size all round but it costs more than $300 for the timber.

Originally Posted by Cliff Rogers

Hooooollllllleeee Sheyet!!! A diesel mechanic.
Struth Ruth.... what the F' are you building???? :eek:

Obviously...a f'ing big bench :eek:

Originally Posted by LineLefty

Hmm yes, I work with engineers whov'e advised me that the job of an engineer is to take the architects design. Remove as much steel and concrete from it until you're just above safety margins. The two Narrows Bridges in Perth look identical, the new one has about 30% less mass than the original. IT's true my workmatesm uni mates ex-girlfriends dad worked on it.

Resurrection time. I worked on a Design and Construct submission for the new Narrows Bridge when I was in Perth. One of the big considerations was the effect of the new bridge's weight on the old one, as it was to be founded well within the zone of effect of the old one's footings and the soil is uniformly muck until a long way down. In the end the weight was reduced using high-strength concrete and post-stressing and the piers were founded way below the existing ones IIRC.

Another major consideration was the effect of the approaches on the existing approach embankment. Our proposal (which didn't get up) was to use polystyrene foam as the core material for the embankment, which is done in sucj places as Finland and Norway to allow roads to be built on permafrost, which would melt under the weight of a conventional road. There were to be 2 types of foam used, of different densities, which would be placed as blocks and tied down to soil anchors deep underground. This was to be covered with a couple of layers of impermeable, fuel-insoluble membrane and the lot covered with pavement. The sides of the embankment would have had a meter or so of topsoil (sand in this case). The overall embankment wold have had the same mass as the meter or so of soil(mostly marine clay) that would have been excavated for it to socket into and thus no net effect on the adjacent embankment. Construction was to be done in stages, excavating and replacing only a few square meters at a time. It was a really brilliant solution, but MRWA went with the traditional (and really expensive) approach of a pile-supported embankment, drilling hundreds of bored piles and driving hundreds of screw piles to help take the weight.

MYTH 3: Having a working DC system (with REALLY snazzy pipe work) is better.

Wrong!!

Ask Midge.

Originally Posted by Wood Borer

.... the farmers would cut down a couple of trees that “looked” strong enough and use them to make a bridge. They never seemed to break!

If you were to ask the farmers what the mass of the vehicles was, they would probably estimate them “she’d be a few ton”. Try and ask them how they knew the logs would be strong enough, and they would tell you they looked OK for a few ton.

Resurrection time 2

One of my favourite quotes

"Anyone can design a bridge that works. The trick is to design one that only just works."
Colin Chapman - Engineer (The bloke who founded Lotus Cars).

Of all the things that our engineering lecturers taught us (Oh, these many years ago, Virginia!) - that one quote from a really good engineer resonated loudest for me. He was a structural engineer, incidentally.

Originally Posted by LineLefty

Hmm yes, I work with engineers whov'e advised me that the job of an engineer is to take the architects design. Remove as much steel and concrete from it until you're just above safety margins. The two Narrows Bridges in Perth look identical, . . . . . .

Errr . . . . . .No, not from underneath they don't.

Photo shows 360 panorama from underneath the two bridges. The lesser mass, younger one is pretty obvious.

BTW the fisherman in the photo is the guy who designed the Sydney Olympics torch up through the water thingo. He just happened to be standing there and asked him if would mind staying in the shot.

I’m of the group that say, a bench is a tool to be used and abused so rather than build a fine bit of furniture my benches are pretty basic.
<o></o>

• All butt jointed frame
• Liquid nails – glue
• Screwed joints

<o></o>Yuk, I hear you say liquid nails but I used rough stud timbers (cheap as chips) so this acted as filler/glue. The whole thing was designed around sheets of seconds ply so tops are two skins of 18mm thick 700 mm wide and lower shelf 18 mm thick 500 wide. A 2.4 long bench took less than a morning to construct.
<o></o>
I regularly climb onto the bench for access to shelving above it and load it with 100 kg cabinets and so far this crude construction is as solid as a rock.
<o></o>
However a lesson I leaned was to be more careful when laminating the two boards to form the worktop, each end has a slight dip/bow – I could plane this out but so far it isn’t a big issue.

Originally Posted by Driver

Resurrection time 2

One of my favourite quotes

"Anyone can design a bridge that works. The trick is to design one that only just works."
Colin Chapman - Engineer (The bloke who founded Lotus Cars).

Of all the things that our engineering lecturers taught us (Oh, these many years ago, Virginia!) - that one quote from a really good engineer resonated loudest for me. He was a structural engineer, incidentally.

The trick in engineering is always to get the most with the least. The bit that Chapman didn't say was that the point at which it has to "only just work" is when it's at the end of its life. Bridges are easy to build light if only they didn't have to last...

Originally Posted by Exador

The trick in engineering is always to get the most with the least. The bit that Chapman didn't say was that the point at which it has to "only just work" is when it's at the end of its life. Bridges are easy to build light if only they didn't have to last...

...and Chapman's racing cars were famous/notorious for mechanical failures when in the lead because he had miscalculated how much of the safety tolerance that every on else used that he could take away - often not because the particular part couldn't last the race, but because some other part put more strain on a part than had been realised.

Just thought I would give my 2 bobs worth about the 'boing' factor. A bench will boing due to it acting like a spring absorbing the energy (deflecting downwards) and then returning it and vibrating eg boing. A heavier bench thicker top will generally deflect less and not boing. It will be providing a better 'reaction force', it is generally stiffer and won't boing. So the initial comment about the heavy bench 'absorbing the energy' is not correct. It is because it returns the energy that it 'feels better' to work with.

The same as working directly above a leg of a bench when you cut mortices for example.

I work with an old metal frame desk that will be replaced in the near future with a solid tassie oak bench with about a 60mm top. When I get around to it.

Cheers
Shannon

For some reason, I missed this thread when it was first posted, but I would like to put in a plea for bolted joinery for the stretchers of a workbench. I have used my workbench in Colorado and QLD for over ten years, and have never had to tighten the bolts - they never work loose. A picture of the stretcher joinery is given in this old post in another thread: http://www.woodworkforums.ubeaut.com...ench#post53170 .

The joint is dead easy to make and rock solid. The two blocks through which the bolts pass are glued and dowelled above and below the stretcher, which is just butted against the leg.

Rocker