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Low profile torsion box questions

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Forum topic by emilime75 posted 07-06-2016 06:46 AM 732 views 0 times favorited 5 replies Add to Favorites Watch
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emilime75

4 posts in 150 days


07-06-2016 06:46 AM

Hey, everyone, new guy here with some questions.

I’m building a rolling workstation for my new to me Unisaw. I want to keep the working height no higher than 37”, and with the saw itself being 34”, that doesn’t leave me a whole lot of height for a tall base. I also need to maintain 1.5” ride height to clear a step down when I roll this out of the garage, so the platform can only be 1.5” tall.

So, my plan was to laminate taller plywood stringers around the Unisaw base, these can be as tall as 10-11” and 3x .75” (2.25”) thick. I would then span the underside with a low profile torsion box. To put it in simpler terms, this can be a torsion box as tall as 11” with a hollowed out section for the Unisaw to sit in. The entire base will be 40”x80”, with the saw being about 12” in from one side.

This is where I’m not sure what to do. Since 1.5” is all I can allow in height, what’s my best option?

A. Simply laminate 2x .75” sheets of plywood?

B. Torsion box using .5” runners and .5” top/bottom?

C. Torsion box using 1” runners and .25” top/bottom?

D. Maybe you have a better suggestion?


5 replies so far

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Nowater

11 posts in 1400 days


#1 posted 07-06-2016 01:19 PM

Your Unisaw probably has a lower base about four inches or so high that extends out from the main lower cabinet. On some models it has a dust collection port on the back of this lower base.

This base can be removed to gain about four inches if needed. If I remember correctly, there are four or eight screws that attach it to the main cabinet.

By the way, some people like a taller table saw so don’t feel like you are trapped in a corner.

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clin

510 posts in 456 days


#2 posted 07-06-2016 04:25 PM

Just laminate two 3/4” sheets of plywood.

Keep in mind that torsion boxes do not have magic properties. They are not stronger or stiffer than something of the same size and material made from a solid piece.

A torsion box can be viewed as a solid piece with the parts, that contribute the least to strength and stiffness, removed.

There are two basic reasons to use a torsion box:

1) Lighter weight than equivalent solid piece.
2) Can be built to exact shape (usually flat) with great accuracy.

Neither of those are requirements in this application.

I think your most difficult issue is maintaining the 1.5” ground clearance. You’ll clearly need caster with wheels much larger than this so it will roll easily and not have small wheels get caught in every little crack or seam in the concrete garage floor.

Also, even with large wheels it will be difficult to get over a 1.5” lip.

So your casters will have to be mounted outside the perimeter of your saw base, and higher up. So you’ll have to transition from 1.5” clearance to 4 to 5” or so. The base on my saw uses a lot of steel to manage that. Assuming you stay with wood, you’ll have to extend the plywood platform out away from the saw and build up an appropriate structure. I think this is where you were saying you can build up as much as 10-11”. You of course don’t need to go nearly that high.

I’d think in terms of something with a 2×4 framing. The plywood saw base attached to the bottom edge of the 2×4 frame, and your casters attached to plywood on the top.

Also, depending on where the weight of your saw is on it’s base, rather than plywood, maybe something like 2”x2” steel angle attached to the 2X frame. And if the weight of the saw is near the edge, there would be little advantage to a 1.5” plywood base. A single 3/4” thickness would be fine.

Rather than focus on 1.5” ground clearance, which again is still going to be hard to roll a 400-500 lb saw plus 100+ lb workstation base, I’d consider building a ramp you can lay down as needed. Just keep in mind that with a simple, straight line ramp, you can still high center if the upper transition from flat to sloped is abrupt.

While my base lifts the my saw over 1”, the frame of the mobile base only has 1/4” of clearance. I have a 1” lip at the front of my garage, and even after I built a very specialized ramp, it still doesn’t work due to unevenness in the concrete.

So while I think with a ramp you can reduce your clearance from 1.5”, I’d shoot for no less than 1/2”.

-- Clin

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emilime75

4 posts in 150 days


#3 posted 07-07-2016 02:14 PM



Your Unisaw probably has a lower base about four inches or so high that extends out from the main lower cabinet. On some models it has a dust collection port on the back of this lower base.

This base can be removed to gain about four inches if needed. If I remember correctly, there are four or eight screws that attach it to the main cabinet.

By the way, some people like a taller table saw so don t feel like you are trapped in a corner.

- Nowater


Dude, that changes everything. I thought this piece was welded but I took a closer look and, sure enough, it’s just screwed on. Thanks.

The working height I chose is based on my current saw + mobile base being at 39”. It’s OK, but I’d prefer it to be a little lower even though I’m 6’1”.

View emilime75's profile

emilime75

4 posts in 150 days


#4 posted 07-07-2016 02:24 PM



Just laminate two 3/4” sheets of plywood.

Keep in mind that torsion boxes do not have magic properties. They are not stronger or stiffer than something of the same size and material made from a solid piece.

A torsion box can be viewed as a solid piece with the parts, that contribute the least to strength and stiffness, removed.

There are two basic reasons to use a torsion box:

1) Lighter weight than equivalent solid piece.
2) Can be built to exact shape (usually flat) with great accuracy.

Neither of those are requirements in this application.

I think your most difficult issue is maintaining the 1.5” ground clearance. You ll clearly need caster with wheels much larger than this so it will roll easily and not have small wheels get caught in every little crack or seam in the concrete garage floor.

Also, even with large wheels it will be difficult to get over a 1.5” lip.

So your casters will have to be mounted outside the perimeter of your saw base, and higher up. So you ll have to transition from 1.5” clearance to 4 to 5” or so. The base on my saw uses a lot of steel to manage that. Assuming you stay with wood, you ll have to extend the plywood platform out away from the saw and build up an appropriate structure. I think this is where you were saying you can build up as much as 10-11”. You of course don t need to go nearly that high.

I d think in terms of something with a 2×4 framing. The plywood saw base attached to the bottom edge of the 2×4 frame, and your casters attached to plywood on the top.

Also, depending on where the weight of your saw is on it s base, rather than plywood, maybe something like 2”x2” steel angle attached to the 2X frame. And if the weight of the saw is near the edge, there would be little advantage to a 1.5” plywood base. A single 3/4” thickness would be fine.

Rather than focus on 1.5” ground clearance, which again is still going to be hard to roll a 400-500 lb saw plus 100+ lb workstation base, I d consider building a ramp you can lay down as needed. Just keep in mind that with a simple, straight line ramp, you can still high center if the upper transition from flat to sloped is abrupt.

While my base lifts the my saw over 1”, the frame of the mobile base only has 1/4” of clearance. I have a 1” lip at the front of my garage, and even after I built a very specialized ramp, it still doesn t work due to unevenness in the concrete.

So while I think with a ramp you can reduce your clearance from 1.5”, I d shoot for no less than 1/2”.

- clin


Yes, I planned on the ends of the base being raised to accommodate a taller caster. Also, the step down I need to clear is only about .75”, I just chose 1.5” for ride height because I don’t want it getting high sided since the whole workstation will be about 80-84” long. I’ve got a 4×8 work table, it, along with all of the “stuff” on a lower shelf makes it over the step down fine with 5” casters. I will probably do either 5 or 6 inch casters on the saw base.

View clin's profile

clin

510 posts in 456 days


#5 posted 07-08-2016 12:00 AM


Yes, I planned on the ends of the base being raised to accommodate a taller caster. Also, the step down I need to clear is only about .75”, I just chose 1.5” for ride height because I don t want it getting high sided since the whole workstation will be about 80-84” long. I ve got a 4×8 work table, it, along with all of the “stuff” on a lower shelf makes it over the step down fine with 5” casters. I will probably do either 5 or 6 inch casters on the saw base.

- emilime75

I see. I would agree that a 1.5” clearance with a 3/4” would work fine.

-- Clin

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