Anniversary bridge rack reproduction

martin35

AzB Silver Member
Silver Member
Martin-
I have gathered from pictures in your earlier posts that you are a machinist.

This will probably make sense to you. I have made a system that mounts on the rail for my planer to cut gradual profiles on longish lengths, with a router and template follower. I have never used it for bending forms because it would not save time for the typical forms or work i get. But a system like this could generate a long M/F form for production. Such as an S-curve.....

As you know, remove the router & with a round nose stick tool in the clapper, it could do steel or Al. :grin-square:

This is sort of pool related - I have shown in the past that the planer is how i make shaft blanks, with a set of centers on the table & a tracer on the left column. :)

smt


SMT

While I've a machinist training and some working experience I'm only a hobby machinist. Actually I'm mechanical designer, I design tooling and machinery but I've always been facinated by the manufacturing processes and machine tools.

I really like this setup, it's creativity at his best. From this post and your post on Practical machinist it looks like you have a very nice collection of vintage machine tools.

Thanks again for posting all those great ideas.


Martin
 

martin35

AzB Silver Member
Silver Member
Awesome post! IMO, this is PRODUCTIVE TALK!! Love it.

cant wait to see your finished product Martin, these Bridge holders will be awesome!

Trent from Toledo

Hi Trent

Ssonerai looks like a fantastic woodworker and he's really generous to share his knowledge.

Dont hold your breath for the final product, it may take me a while to start the project, I've some other more boring stuff to do before but I want to gather as much information now, while the knowledge is available.

Martin
 
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martin35

AzB Silver Member
Silver Member
Dimensions

Guys

Here is a quick drawing with dimensions. I've only rough guessed the dimensions. Any contribution is welcome to put the right dimension on the drawings. Picture with tape measure is fine also

Thanks

Martin

View attachment bridgerack.pdf

2019-08-15 20-48-49.jpg
 
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Ssonerai

AzB Silver Member
Silver Member
Martin -
this is interesting enough i did some very preliminary tests.
You will need to specify a thickness.

What i suspected, and actually found to be a problem is bending 1/16" (.062") thick maple veneer over the 1" radius section. The pressure seems low enough, no scales used yet - but the veneer cracks or completely breaks.

In a complete supporting bundle with a pressure source that started on the apex and proceeded both directions, that thickness is do-able. But it requires good process and is not "automatic". (Some bundles might be fine, a few might have failures, due to the random nature of wood.) I have to confess that the only 1/16" scraps laying around here is BE, so marginally/possibly "unfair" test. However, BE at .048" thick bent fine. .055 was acceptable.

At this point, the total bundle thickness would start to define the number of layers (needs to be odd number) and the thicknesses. Not all layers have to be the same thickness, but it complicates strategy and inventory if they aren't. :smile: Thinking about it, i never saw other than the recent pix of the product you are contemplating making; however it was not at all unusual to use different thickness core veneers, and thinner face veneers. I don't find that an advantage for small batch production. The product won't look any different. But if you are hoping if fools the conservators, then you have to do similar lay-ups to what BBC did. ;)

I'll get photos later or tomorrow.
OTOH I based my set ups on (guessed) 3/8" thick total part thickness.

smt
 

Boxcar

AzB Silver Member
Silver Member
Martin,

I have a suggestion but it will prove to be labor intensive.

After you have built your mold forms, build a steam tank large enough to accommodate your veneers. If possible, drop back to a thinner veneer. Steam one veneer at a time and get it very flimsy and pliable. Put it in you press, clamp it, and let it dry. If you find out that you can do two at the time without damage to the veneer, that will speed the process. The dried veneers should almost hold their shape. After you amass the desired number, uniformly apply a thin, slow curing glue to one side of each dried veneer, mount appropriately in the press, and clamp. Don't use so much glue that it hydraulically forces separation between the layers. Allow the blank to cure completely in the mold press. Remove when dry and shape.

BOXCAR
 

martin35

AzB Silver Member
Silver Member
Martin -
this is interesting enough i did some very preliminary tests.
You will need to specify a thickness.

What i suspected, and actually found to be a problem is bending 1/16" (.062") thick maple veneer over the 1" radius section. The pressure seems low enough, no scales used yet - but the veneer cracks or completely breaks.

In a complete supporting bundle with a pressure source that started on the apex and proceeded both directions, that thickness is do-able. But it requires good process and is not "automatic". (Some bundles might be fine, a few might have failures, due to the random nature of wood.) I have to confess that the only 1/16" scraps laying around here is BE, so marginally/possibly "unfair" test. However, BE at .048" thick bent fine. .055 was acceptable.

At this point, the total bundle thickness would start to define the number of layers (needs to be odd number) and the thicknesses. Not all layers have to be the same thickness, but it complicates strategy and inventory if they aren't. :smile: Thinking about it, i never saw other than the recent pix of the product you are contemplating making; however it was not at all unusual to use different thickness core veneers, and thinner face veneers. I don't find that an advantage for small batch production. The product won't look any different. But if you are hoping if fools the conservators, then you have to do similar lay-ups to what BBC did. ;)

I'll get photos later or tomorrow.
OTOH I based my set ups on (guessed) 3/8" thick total part thickness.

smt

SMT you keep impressing me with your will and generosity. At the beginning I wa talking about 1/2 th. but I Thnik it's way too thick, I think 3/8 is probably plenty enough maybe even 5/16"th. may work. Excuse my ignorance but what is BE ? Theproduct I've posted here is also offered with 0.045" core sheet, I guess that the top layers may be planned down to about the same thickness for easier bending and it gives a total thickness of 5/16"

I also like Boxcar's idea. It makes me think about an intermediate solution. I agree that steam is probalby the best solution but I wonder if soaking the sheet in water to soften them up and as Boxcar suggest preforming them in the form and let them before to glue may work....

Thanks for everything guy.

Martin
 
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martin35

AzB Silver Member
Silver Member
Martin,

I have a suggestion but it will prove to be labor intensive.

After you have built your mold forms, build a steam tank large enough to accommodate your veneers. If possible, drop back to a thinner veneer. Steam one veneer at a time and get it very flimsy and pliable. Put it in you press, clamp it, and let it dry. If you find out that you can do two at the time without damage to the veneer, that will speed the process. The dried veneers should almost hold their shape. After you amass the desired number, uniformly apply a thin, slow curing glue to one side of each dried veneer, mount appropriately in the press, and clamp. Don't use so much glue that it hydraulically forces separation between the layers. Allow the blank to cure completely in the mold press. Remove when dry and shape.

BOXCAR

Thanks Boxcar

I think it's a great idea.

Martin
 

martin35

AzB Silver Member
Silver Member
I also found that kit from a supplier in Montreal, looks similar to the other one. BTW if you have another material to suggest, I'm open to suggestion, I was looking at maple because it was easy to find and can make a strong assembly but it can be sothing else.

Thanks

Martin

https://www.langevinforest.com/en/skateboard-veneer-kit
 
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kid

billiard mechanic
Silver Member
Maybe just a simple sheet of aluminium with the same finish as the corners could be nice ..


Envoyé de mon iPhone en utilisant AzBilliards Forums
 

martin35

AzB Silver Member
Silver Member
Maybe just a simple sheet of aluminium with the same finish as the corners could be nice ..


Envoyé de mon iPhone en utilisant AzBilliards Forums

Hello Kid

Nice to hear from you.

I like the idea but I wonder if the Aluminum may damage the bridge stick, but on the other hand it's only a bridge and not a cue.

I think it's good idea but I had my share of aluminum polishing for a while.

Thanks

Martin
 

Boxcar

AzB Silver Member
Silver Member
Martin,

You will enjoy the website known as:

Constantine's.com

They have a vast inventory of veneers. You may be delighted to find the "Flexible" veneers sections.

Best regards,

BOXCAR
 

Ssonerai

AzB Silver Member
Silver Member
Martin -

Not being intentionally generous :wink:
This is interesting enough that it informs other work i do.
And it is relatively fast to prototype. Cnc router would be really fast. I'm oldschool and use pinrouters and such. So once a master is made, it is quick to duplicate, make the mating part, etc, etc.

The 90° bend seems borderline to me, so i wanted to be sure i was not mis-stating anything. I'll show the work, then discuss some factors to improve the process. This computer times out too fast and the post gets lost.

First photo is 2 layers 1/16" thick birdseye maple, it is black because it was scrap form a project that used it ebonized. I tried this several times with no success. Only 1/16" i had on hand other than mahogany, which also broke immediately.

Second photo is 3 layers Birdseye maple, .048" thick - success!

3.) is 6 layers .048" BE & plain mixed. This is thicker than the press design, and even at that small difference, begins to show errors - there is a gap at the peak of the 90° bend if you look closely.

4.) is the press design thickness at .260" and includes 5 layers .048" + one layer compressible naugahyde at .039" for compliant pressure. Adding a compressible layer on the follower side helps immensely to force conformance with the control surface.
 

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Ssonerai

AzB Silver Member
Silver Member
The only reason the press design thickness was .260 in the above example, is that the follower pattern was directly routed from the master. The pin was a bit larger than .250, a .250 router bit was used, and light sanding cleaned it up. So in this case, convenient tooling defined the follower space. :)

I wondered what kind of force it would take to close up the press, after the strips had been clamped already for previous pics. This is really crude, but informative. (Part of my weight is resting on elbows to steady the camera; I do weigh a little more than shown) Not clearly visible, but 150 lbs is not really enough to fully force compliance at the 90° peak; however it gets most of it.,

On the real form, the angles need to be slightly exaggerated - like maybe 89° instead of 90°. 136° instead of 135°. It all depends on thickness and number of lamina, and the type glue.

It is better if the control form is really stiff and rigid. However, the follower should be a lot more flexible than shown. it should be able to conform to the control, so long as it adequately presses the veneers in hard on the tricky areas.

The strips are 1-1/2" wide. So if it takes 150lbs to "mostly" attain the form, that is 100 lbs/inch width. the strips are 11" long, but most of the pressure is concentrated on about a 5 or 6" section. So 16 - 20 lbs/in^2. This is where vacuum gets iffy. It might pull it all down, but it is borderline at the veneer thickness and total part thickness. Not all your layers would be long grain, so that is in your favor, wood bends easier "sideways". The good thing about vacuum is that at this thickness, i doubt there would be voids. It just might not pull down exactly to form. I would definitely do a dry run and include every step.

good luck!
smt
 

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Boxcar

AzB Silver Member
Silver Member
I apologize for this interruption. You certainly already know this, but the grain of the bridge rack runs at right angles to the grain of the veneers in your demonstration. You have achieved remarkable results with your multi layered veneer sample.

Best regards,

BOXCAR
 

Ssonerai

AzB Silver Member
Silver Member
Boxcar - Sounds like you've bent and veneered a few things!
Unless i interpreted the pictures wrong, the grain goes both ways, like common plywood. That would also be the only really practical way to make the full length part.

As you are allowing, the crossways grain (to the shape) is the most difficult, so i just did the pressures and such "worst case". Always better to find the real thing goes easier. It would be worth bending a few parallel grain samples over the peak by hand - won't take much pressure at all, but worth finding out how likely it is to break.

Still, big changes occur with small differences in veneer thickness, total thickness, and small details like just making the 90° radius larger.
So from here the jury is out until some actual measurements or comparison with a real part happen. :smile:

PS: It looks like Blat Billiards gets their veneer from certainlywood in East Aurora, NY. (Buffalo).

smt
 

Boxcar

AzB Silver Member
Silver Member
SMT,

You do amazing work and it is clear to see that you always evaluate the variables.

Your table aprons are fantastic. It appears that the grain of each ply runs long. Is that what I am seeing?

I think the original bridge racks were three-ply. The outer plys certainly ran long. Was the inner ply laid at right angles?

It's been years and I have forgotten a lot. Did Plycraft and Knoll/Eames chairs lay up on the cross or long?

This is an interesting study. Thank you.

BOXCAR
 

Ssonerai

AzB Silver Member
Silver Member
Worth clarifying a couple points.
The questions a bending project poses are 1.) will vacuum bend the parts (will it develop enough pressure, since the limit is 14PSI. 2.) what thickness veneer will bend over/into the worst section radius reliably without breaking.

Vacuum (or generally, also pressure bladder) will bend thicker veneers without breaking them, than a 2-part top/bottom hard press, because the vacuum pressure starts on the peaks, and "smooths" the material out and down both sides while compressing and supporting it at, over and around the peak.

Veneers which break when hand bent for trial over the difficult sections, may vac or pressure bag press successfully, yet pop grain here and there on thick faces when removed from the press. However, these considerations show why thicker core veneers can be used successfully with slightly thinner face veneers.

smt
 

Ssonerai

AzB Silver Member
Silver Member
Boxcar - you and i were typing at the same time. :)

Thank you for the very kind words.

It appears that the grain of each ply runs long. Is that what I am seeing?

No, these have alternating layers just like plywood.

The "old dead guys" often veneered burl right over solid wood for curvy stuff, because burl will sort of shrink/expand both ways. On better work where a cross band could be applied, they did use that.

I did not want the risk of uncontrolled shrinkage or expansion for several reasons. I did not want the drawer space to vary, did not want the risk of veneer popping, and the interior dividers are plywood again for stability, so not making the outer skirts the same would risk the carcass fighting itself over time and seasons change.

i neglected to take pics of the actual stacks laid up for bending; but here are some from veneering them that show cross plies. The inner cores are the same, alternating layers.

Ray and Charles Eames chairs, and all the clones ever after are full plywood alternating layers of cross and long grain.

The replica curved church pews i built ca 1991 for a congregation that had expanded their building always puzzled me as to how they did things in the 19-teens. With only hot hide glue to work with!. The backs of the original pews had a very thin center cross band, and thick outer plies. I have always wondered how they bent the 3-d shape back then. End to end long radius is easy, of course. But the top to bottom S-curve "Back shape" added onto that must have taken an interesting press. I do know they used concret forms for some work at least by the early 1920's but have no idea if that was applicable for the church pews. For modern work it was easy with a single side form, WEST, and vacuum.
 

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Ssonerai

AzB Silver Member
Silver Member
Limit 5 photos per post.

This is the underside of the bottom panel. QS sycamore.
There's a story behind sheltering under (in) hollow sycamores in the clients family history.

smt
 

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