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  #1  
Old Tue 23 February 2010, 12:31
giggler
Just call me: giggler
 
na
United Kingdom
Space use and Shopbot table designs

Hi,

I'm new here and this is my first post. I have seen the plans for MM and have noticed there are supports all around the table. This means I'd have trouble using the space under, since it would be a good storage area for flat sheet material.

I have an old document that Shopbot produced for international customers. They used to sell there Alpha's in kit form as just the rails and Y section to cut down on shipping. They offered plans to build there standard 8'x4' router table.

Looking at there document, it seems they are using larger C channel section for table sides and legs (C6x8.2), interestingly they only have angled gussets on the table ends, so the entire middle of the table is free from obstruction.

Is this something I could use as a design for the table and basically retrofit the Y section on it? Or more importantly, can I remove the table side supports if I use larger gauge leg and side material like shopbot?

dc
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  #2  
Old Tue 23 February 2010, 13:45
xraydude
Just call me: Ted
 
New Orleans, LA
United States of America
giggler, I saw a thread in which this question was asked and Gerald linked to the old forum here: http://www.mechmate.com/Forum/messages/2/44.html

Shows a table design that a gentleman used to create storage under his table. I am in the process of getting my steel in to construct my table, and am also planning on using the space underneath for some sheet goods storage, as I simply do not have enough space in my shop as is. The design I am planning on using will allow sliding 4' x 8' sheets in from the front, but still utilizes all of the vertical bearing pieces on the X side of the table as well as the rear Y.
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  #3  
Old Tue 23 February 2010, 19:44
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The lighter you build the table, and the less cross bracing you put in, the more it will shake. It is as simple as that.
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  #4  
Old Tue 23 February 2010, 20:46
JLFIN
Just call me: Jim
 
glenwood iowa
United States of America
I would think you could move the bottom rail (on ends) up probably a third and gusset as shown, then gusset under rail leaving access for a low sled to slide under. After all, still stronger at that point then the adjusting pad bolts people are using for leveling pads
(just a thought)
happy build
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  #5  
Old Tue 23 February 2010, 22:12
swatkins
Just call me: Steve
 
Houston
United States of America
I am working on a easy solution that will allow access to that area for sheet goods, while retaining all the strength and structure of the table. As soon as I get it drawn up, figuring out the last details now, I will share
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  #6  
Old Tue 23 February 2010, 22:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
A shaking table happens when the whole MM goes into resonance, and this depends on the type of cutting. A lot of rapid changes in direction, like cutting small text in signs, is the worst case. If you are only going to be cutting rectangular cabinet parts, the table can be quite a light construction.

Another factor is that you want the table to stay "true" after you have accidently smacked the side with a big board . . . . . . .

Last edited by Gerald D; Tue 23 February 2010 at 22:18.. Reason: Merged 2 posts into one
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  #7  
Old Tue 23 February 2010, 22:38
xraydude
Just call me: Ted
 
New Orleans, LA
United States of America
hmmm... Gerald you must have seen me work before. I usually end up smacking everything!

For me, making it light is not a design criteria. Incorporating the storage space will be secondary to a strong, heavy table.

Steve, please do share when you get the details worked out.
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  #8  
Old Wed 24 February 2010, 02:28
giggler
Just call me: giggler
 
na
United Kingdom
I should say the designs were for their PRTalpha 96, not PRS. Weight wise the sides are C6x8.2 channel where each weighs approx 41Kg.

Probably a better question would be ask has anyone added up all of the metal structures for the MM table? I can do the same for this PRT design and see what figures we come out to?

Perhaps I'm missing something other than weight as I thought only about how rigid the table might be until now.

dc
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  #9  
Old Wed 24 February 2010, 06:13
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
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I found out that I have a bit of resonance, but I sorted it by fixing the sides of the table to a brick wall.
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  #10  
Old Wed 24 February 2010, 06:44
giggler
Just call me: giggler
 
na
United Kingdom
Kobus_Joubert,

Ok thanks. So what I want to know is, do people with the ShopbotPRT's have the same problem? (now I have that answer about MM, perhaps I should ask in shopbot forum, doh!)

If because the materials on the PRT's are thicker gauge, they don't have similar resonance problems then I could see myself building that table and retrofitting the Y axis onwards AND keeping good space for storage.

dc
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  #11  
Old Wed 24 February 2010, 08:59
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
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Just remember I took steel that I had and my wiggles are not due to Gerald's design, but due to available material on that day.
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  #12  
Old Wed 24 February 2010, 10:26
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
dc, the SB people most certainly have the resonance issue.....but they will all deny it at their forum .
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