[Tone Depth]

You need to keep the legs (uprights) from moving relative to each other to minimize the twisting motion(I'm an engineer).  The connections between the shelf supports and the legs aren't strong enough to resist the twisting you've observed.  There are several approaches:
1.  Put some diagonals in between adjacent legs.  Aesthetically, this could be your turnbuckle and wire system, since you probably wouldn't want to be able to see solid diagonals.
2.  Bolt a plate to the back legs, fastening at least twice on each leg.  Cut holes for interconnects and power cords to pass through.  This can hide the cords from being seen from the front of the rack.
3.  Figure out stronger connections between the shelf supports and the legs.

Hope this helps.

[lonewolfny42]

That video demonstration has got to be a new first for Audio Circle. 

I believe so...and I try to read everything.

Thanks Martin...

[mhconley]

Thanks for the comments and suggestions.  I'm glad you liked the videos... 

As I was drifting off to sleep last night I had a moment and I now know why my rack twists, how to resolve it without compromising aesthetics, and why I am sure Adona’s racks do not twist.

Where my “X” shelf supports attach to the legs I used a single 3360 anchor fastener.  These fasteners are among 80/20’s strongest.  The issue is that the fastener uses a single 5/16” socket head cap screw in line with the shelf support.  This single screw allows the leg to pivot ever so slightly about the axis of the shelf.  These shelf fasteners and the weight of the top turntable shelf are what allow the rack to twist.

I believe I can fix this by using the 3098 double anchor fastener.  It uses two 5/16” socket head cap screws, one each top and bottom of the shelf support.  These two attachment points would not allow the joint to pivot.  I believe all shelves anchored with these fasteners would mitigate the twisting issue.  If the double anchor fastener does not prove twist resistant enough I can use the 3368 inside corner connectors which I believe definitely would stop the twisting.

I believe Adona’s racks will not twist because they use a different type of cross shelf support that uses attachment points above and below each shelf support.

Martin

[toobluvr]

Hey Martin...

Do you need counterbore holes at the end of the "x" member to use those 33xx fasteners?

If so, you will need another one at each post attachment point.
Can you do it, or must it be done at the factory?
Big hassle if the latter!

To attach your cross members to the posts, have you considered simple 8020 "L" brackets like I used?
Think they would work?

[mhconley]

Both anchor fasteners require counterbores, the "L" brackets and inside corners do not.  I had all counterbores done by 80/20 prior to shipment.  So my rack may stay as is.  I am OK with it as is - it takes quite a hit to get the thing moving.  If I disassemble my rack to shorten the legs then I may add something to stabilize it.

I looked at using the 4301 “L” brackets and dismissed them due to cost.  I need to revisit that decision.

Total cost including cap screws, t-nuts and machining for each type of connector:
3360 Single anchor fastener - $5.75
3364 Inside corner - $9.00
4301 “L” bracket - $9.10
3098 Double anchor fastener - $11.00

Martin

[toobluvr]

I used the 4302 "L" bracket.  They were only $2.95 each....lots cheaper than one you looked at!
No good for you?

[mhconley]

The 4302 has a single bolt attachment to each piece.  I think it would have the same pivoting issue in my application.  Unless I used two, one on top and one on bottom.  That's why I am looking at the 4301.

The 4302 is $5.09 including t-nuts and cap screws.

Martin

[toobluvr]

The 4302 has a single bolt attachment to each piece.  I think it would have the same pivoting issue in my application.  Unless I used two, one on top and one on bottom.  That's why I am looking at the 4301.

The 4302 is $5.09 including t-nuts and cap screws.

Martin

Right....I did not include all the fastening hardware.

I paid a bit less than that.......$4.15 for the whole assembly:

4302 corner bracket:                              2.95

3838 economy T-nut @ .32 ea:                .64 for 2

3813 button head cap screw @ .28 ea:      .56 for 2

[mhconley]

You're prices are correct - I had the wrong price for the cap screws.  And I forgot you used the 4040 metric profile and metric fittings.

5/16"-18 x 11/16" button head caps screws - 28 cents
single economy 5/16"-18 t-nut - 27 cents
double economy 5/16"-18 t-nut - 79 cents

The correct prices with hardware and machining:
4302 2 hole "L" bracket - $4.05
3360 Single anchor fastener - $5.75
4301 4 hole “L” bracket - $7.02
3364 Inside corner - $9.00
3098 Double anchor fastener - $11.00

Martin

[erimille]

I was also very surpised by this twisting.  Here are two short videos of the rack at its worst.  It takes considerable effort to get the rack twisting as in these videos but a slight bump will move it too, just much less noticeably.

I've found twisting a fairly common artifact of that particular cross-beam design [1]. That said, it's one I haven't found to be a design defect per se. Having now built a few of these types now (as well as a handful of the FleXys) and testing these side-by-side I much prefer the isolation properties of the "twisty" over the "flexy" The key is to not hit it hard enough to move - that rule works for any kind of rack

Excellent job on the design; very impressive work!

--e

 [1] http://potlach.org/2007/10/radials/radials-Pages/Image6.html

[toobluvr]

Really cool rack, Erimille.

I like the modular approach and the flexibility it offers in using it either
vertically or horizontally....similar to VTI and Lovan, but nicer!

Nice job!
 

[mhconley]

I'll echo John's comments - that is one nice rack, Erimille!

Looks like we were thinking along the same lines spike-wise.  I love that your's is completely realized in wood.  Too cool!  I also like the flexibility of the separate levels.  I was trying to figure out how to do that with the extruded aluminum but could think of no simple, inexpensive way to cap the tops and provide a positive coupling for the spikes.  I see you incorprated the floor protector discs into the tops of the posts - neat idea.  80/20 has plastic caps that would work but I thought they may have been a little cheesy.  I guess I could drill holes in the caps and set the floor discs in the hole on top of the extrusion...

Martin

[woodsyi]

Any thoughts would be greatly appreciated.  I have sent the problem to my local 80/20 dealer and will see what they have to say.  I have also downloaded a trial version of Autocad and 80/20's plug-ins and may try playing with this myself.

Martin

Martin,

Adding another X frame at the top and resting the top shelf on it may help.  Adona racks do (as you said) have welded plate at the end of the steal x-frames that allow two screws --one above and one below the x-frame -- to attach to the rack posts. 

[toobluvr]

Martin...

caps are available from 80-20.  See in my photo here:



Don't know the cost.
If you leave the middle screw out, you could anchor the spike right into the hole that is pre-drilled down the middle of the post.  Sans screw, you would just need to glue the end cap to keep it in place.

[mhconley]

The caps look nice.  I thought they were held in place with plastic push pins?  I like the T-slot covers, too.  They dress it up a little bit.

Martin

[toobluvr]

The caps look nice.  I thought they were held in place with plastic push pins?  I like the T-slot covers, too.  They dress it up a little bit.

Martin

The screw down the middle holds the cap in place.

I tried using the T-slot covers, but I decided I prefer the look without them.

[mhconley]

I am building another, shorter three shelf rack using the 1501 profile on the legs and 1515-L for the shelf supports.  I am scaling it back slightly using the lite material, 1-3/8" shelves with a 1-7/8" top shelf.  This new rack will go up for sale to test the waters...

Martin

[toobluvr]

I am building another, shorter three shelf rack using the 1501 profile on the legs and 1515-L for the shelf supports.  I am scaling it back slightly using the lite material, 1-3/8" shelves with a 1-7/8" top shelf.  This new rack will go up for sale to test the waters...

Martin

I think that's a smart move, Martin.
 

Keeping it lower will increase stability and rigidity, and I think should make it less prone to twisting.  Plus, I think a lower rack just plain looks better....better propotioned.  If you need to add more gear, just add another single wide rack...or build it double wide now like I did.

I'm over six feet and my rack is much lower than yours, so ease of use is not an issue.  But visually I'd still prefer it a bit lower.   And TT is easier to use at waist level than at chest level.

My uprights are 36 inches long, but once the spikes to floor and top BB shelf are added, it is 40 inches high.  And TT is even higher with the BB platforms underneath.  I have enough height between shelves, so I'm thinking of chopping it down just a bit.

Have you considered the rounded profiles?  Like maybe 1012 or 1517 (fractional), or 40-4030 lite (metric)?   Or even the triangular ones with one flat side:  40-4030 lite (metric) or 1547 (fractional)?  I think they look really sweet, and make an attractive alternative.  If I to build another I would probably use one of them.

Carry on, and keep us posted!
 

[mhconley]

My rack did turn out a little too high... that is why I am considering cutting it down.  It is usable as is and the turntable is at the same height it was on top of where it prevously sat.  I was thinking 48" to the turntable shelf when in reality I added 2-1/8" for the bottom spikes, 1-1/2" for the top spikes, and 2-7/8" for the shelf to bring the total height to 54-1/2".

The rack I am building will have 30" legs and stand 35-7/8" to the surface of the turntable shelf.

I may end up calling it the TwisTy Rack. 

I looked at the round and triangular profiles and think they would look great using a square shelf supports but I don't think they match up well to my "X" shelf support design.

Martin

[erimille]

I may end up calling it the TwisTy Rack. 

I like it!

--e