Shopsmith Forums

algale wrote:With the 92 pound DW735 planer sitting atop the stand for the last several days, I measured the sag at the center of the front edge of the top as 0.019 inches. I measured the sag by placing a straight edge across the sides and inserting a feeler gauge in into the gap in the center.

This was actually very close to what the "Sagulator" suggested it would be. For those not familiar, the Sagulator is an on-line program that purports to calculate how much sag you will get in a beam or shelf based on the materials used, their dimensions, and the load. Here's the site: http://www.woodbin.com/calcs/sagulator.htm Based on my dimensions, material and load, the Sagulator calculated the sag would be 0.02 inches.

As an experiment I tried JPG's suggestion of laying some temporary fir strips left over from another project across the top (left to right) which were long enough to over hang the sides. What I had on hand measured about 1.22 x 1.50 so they were a little lighter weight than what JPG suggested (2x?). With the strips in place, I measured no change in the sag between the bottom of the front strip and the center of the top, which is a very counter intuitive result.

I am still undecided whether to convert this stand into storage (as Ed has suggested) or keep it as a planer stand. I have run a few boards through it, the largest being a six foot length of fir 2 x 10, and the stand seems sturdy in spite of its relatively light-weight construction. When I lock down the casters and put boards through the planer there is no observable wracking or wobbling of the stand. Nor does the stand wrack or wobble when I roll it over the shop floor with the planer sitting on top (although I haven't run the stand over or into any obstacles, which I think is what Ed feared). Maybe I'llg put a similar weight (couple bags of sand) on top of the stand and push it across over the threshold between the finished and unfinished parts of the basement and see what happens.

Decisions, decisions.

Al

Being an EE, and not an ME, I cannot calculate a safety factor for your stand. But I have worked closely with many ME's over the years. I well remember one quoting an ME professor as saying 'Safety factors should really be called "ignorance factors". If we actually knew exactly how a given material would behave, there would be no reason for a "safety factor."'

So maybe your observations account for unexpected anomalies and circumstances. Or maybe they don't. Perhaps the accumulated experience of the folks that advised beefier construction are over-conservative. Or perhaps they are not. Personally, I plead ignorance, and thus I would tend to go with the accumulated wisdom.

If it is electrical, and I thoroughly understand every aspect of the physics involved, I am comfortable with a 20% safety factor. If it is mechanical, on the other hand, and I do not have an ME to analyze the design (mostly for hobby stuff), I go with a conservative gut feeling, and then make it at least four times as strong as that. And then stress-test it to that safety factor or higher. All of which makes it inexpensive to design, but would also make it prohibitively expensive to manufacture in any volume.

Hmmm. Risk analysis. The key input variable being the price of that nice DW735.

JPG40504 wrote:JPG also said to place them front to back(no gaps between them).

I be curious what the sag measured with the planer removed(i.e. has the top taken a semi-permanent sag?)

JPG does not know that the 'feet' of the planer look like.


Besides JPG agrees with Ed - static OK - mobile maybe not.

P.S. What does the sagulator say re using a 2x 10 pair?

1. Re: No gaps. I missed that before. I misinterpreted as just strips under the edges.

2. Re: Sag with planer removed. I measure it at 0.010. So it appears to have some degree of permanent sag. Can't rule out, however, that there wasn't some amount of cupping in the ply before construction began.

3. Re: Feet. "Feet" is probably a misnomer. Planer sits flat on casting outline. Will try to get and post photo.

4. Re: Mobile maybe not ok. Mobile on a relatively smooth, level shop floor surface is demonstrated to be no problem. 'Tis the potential for sudden stops/jolts by running over/into shop floor obstacles (power cords, cut offs, etc.) that I think has Ed worried about the stand collapsing. Like the old joke says, it's not the fall that will kill you, it's the sudden stop.

5. Re: Sagulator calclation with a 2x10 "pair." The Sagulator doesn't work that way. Sagulator only works for a single shelf or beam with a single load. One obviously could calculate the 92 pound load across a 4 x 10 (a double 2x10) or half the load (46 pounds) on a single 2x10 but I don't know that would really be the same as a 92 pound load spanning two separate 2x10s.

Al

BuckeyeDennis wrote:Being an EE, and not an ME, I cannot calculate a safety factor for your stand. But I have worked closely with many ME's over the years. I well remember one quoting an ME professor as saying 'Safety factors should really be called "ignorance factors". If we actually knew exactly how a given material would behave, there would be no reason for a "safety factor."'

So maybe your observations account for unexpected anomalies and circumstances. Or maybe they don't. Perhaps the accumulated experience of the folks that advised beefier construction are over-conservative. Or perhaps they are not. Personally, I plead ignorance, and thus I would tend to go with the accumulated wisdom.

If it is electrical, and I thoroughly understand every aspect of the physics involved, I am comfortable with a 20% safety factor. If it is mechanical, on the other hand, and I do not have an ME to analyze the design (mostly for hobby stuff), I go with a conservative gut feeling, and then make it at least four times as strong as that. And then stress-test it to that safety factor or higher. All of which makes it inexpensive to design, but would also make it prohibitively expensive to manufacture in any volume.

Hmmm. Risk analysis. The key input variable being the price of that nice DW735.

I picked it up in used mint condition for $350 a couple years ago. Not sure what the does for the risk analysis.

algale wrote:I picked it up in used mint condition for $350 a couple years ago. Not sure what the does for the risk analysis.

Nice stea.. uh, deal!

algale wrote:I picked it up in used mint condition for $350 a couple years ago. Not sure what the does for the risk analysis.

What matters is the replacement cost, not the original procurement cost!;)

I chose 2-2x10 so it spanned the front to back distance(21"?).

You got excelent advice above in doing over your stand. Thought I'd throw in photos of my stand. It is from plans of "The garage workshop" from Norm Abrham. I had to cut down on the upper level to have room for the planer on the lower level. This cut back the drawer by 2" less deep. No problem.
Side of the cabinet with open tool drawer - this drawer is where I keep hammers and other heavy stuff.
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This is the back of the cabinet storage for junk stuff
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Here is the cabinet's home - out of the way - you can see the front opening of the lower cabinet
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Now days, the front top of cabinet is home to my belt sander.

Well, in spite of all the good advice I received to abandon or re-purpose this project, I went ahead and finished the planer stand. I did reinforce the construction with some additional screws through the bottom into the sides and may yet add some through the top. But, surprisingly, this is quite sturdy and rolls readily around the shop with the planer on top, my compressor below and a couple of nail guns in the drawer. It isn't fine cabinetry, but this project involved a number of firsts for me and was a good learning experience.
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For me, this was the first time I built and installed a drawer. The drawer is all 1/2 ply (except the decorative/false front, which is 1/2 red oak which I joined and planed from a rough piece of oak I had laying around). The drawer construction is tongue in dado on the sides/front and back; the bottom also sits in a dado. The handle on the drawer was from a set that used to be on our kitchen cabinets until we replaced them. The slides are full extension slides from the Borg.

To install the slides, I went and bought a fancy plastic jig from Kreg that was supposed to simplify the installation. I generally am impressed with Kreg products. Not this one. The magnets built into the jig to hold the slide aren't really strong enough and the first slide wasn't installed square to the cabinet. Ultimately I found I had better luck just drawing a line with a square and using the square to make sure everything was even before marking the screw holes with a punch. I will be returning the jig.

Also a first for me was building installing a door for the cupboard section of the stand. The construction is panel in frame. The panel is ply (slightly less than 1/4 inch) and the rails/stiles for the frame are white oak scraps I had laying around, jointed and planed down to 1/2. The hinges for the door are also from the Borg. Lousy instructions came with them and I had to relocate the upper hinge on the door side.

The finish is simple Tung Oil. Unfortunately, as you can plainly see, the drawer front is red oak and the stiles/rails are white oak. And neither matches the rest of the cabinet which is "sand ply" from the Borg of unknown species. So, nothing matches. But this was more just to see whether I could do it.

Al

Hey, Al;
That is a fine looking cabinet - Nice Work!:) Congratulations!:D

Yes, we gave advice, and in the final analysis, you did what you thought was right. Looks like your cabinet will last for a long time.

Also - nice thought process to use wood you had available. You can be proud of the wood diferences every time you see the cabinet:D After all it is for your personal use - not for other's enjoyment.

charlese wrote:Hey, Al]That is a fine looking cabinet[/color] - Nice Work!:) Congratulations!:D

Yes, we gave advice, and in the final analysis, you did what you thought was right. Looks like your cabinet will last for a long time.

Also - nice thought process to use wood you had available. You can be proud of the wood diferences every time you see the cabinet:D After all it is for your personal use - not for other's enjoyment.

Thanks, Chuck, I've seen enough of your work on the forum to know that you are being very generous in your evaluation. That or the dim light/soft focus of the pictures has hidden the cabinet's many flaws (but I know where each of them is).

the cabinet looks good for sure! it looks like it still may be sagging along the open lip though. I am a big believer of face frames, as previously suggested. Even 3/4" ply is going to flex with that kind of weight. I build guitar speaker cabinets from 3/4" baltic birch ply for that reason, you do want some flex for that application. Maybe if you topped it with a piece of solid wood (birch is a favorite of mine)?