Davide Sora

Titanium neck heel reinforcement

Recommended Posts

 
 

I saw this interesting article by Stewmac : http://www.stewmac.com/Materials_and_Supplies/Truss_Rods/Non-adjustable_Rods_for_Neck_Reinforcement/Titanium_Neck_Reinforcement_Rod.html

I wondered if anyone has ever tried to use titanium instead of carbon fiber to reinforce cello heel or even violin and viola heel.

It seemed interesting because certainly titanium has a certain durability in the long term, while the synthetic resin that holds together the carbon fiber does not guarantee how it will behave in 50 or 100 years.

Opinions?

Share this post


Link to post
Share on other sites

I don't think you need this for structural strength,  guitar and maybe bass need it, but not for vn or cello.

Some cello makers believe they stabilize neck projection, but that is misguided.

I doubt any tonal improvement.

KYC

Share this post


Link to post
Share on other sites
3 minutes ago, chungviolins said:

I don't think you need this for structural strength,  guitar and maybe bass need it, but not for vn or cello.

Some cello makers believe they stabilize neck projection, but that is misguided.

How so? Most major makers are doing it with cellos these days, and there's quite a bit of experience with it. I have about 40 years of experience with it just myself.

Share this post


Link to post
Share on other sites
3 hours ago, chungviolins said:

Cello neck goes downn bc the cellop top compresses,  not bc the neck/fb bends.

KYC

Then why does the neck go down a lot less when it's reinforced, and why can you see the bend by putting a straigtedge against the back of the heel on a neck which has been removed?

It sounds like you either haven't given much thought to this, or haven't been paying attention while doing repairs. Sheesh, I noticed this stuff when I was about 20 years old. How old are you now?

Since you are featured as the "master repairman" at a Chicago shop, you might want to start being a little more careful, observant, and insightful.

Share this post


Link to post
Share on other sites

Davide, I don't see why titanium wouldn't work, but I'd think it would be susceptible to the same bonding material failure as carbon fiber, if it was glued in place.

I've mostly stuck to wooden dowels, in the belief that some future repairman will be less pissed at me if he runs into the reinforcing material with his nice sharp cutting tools. :lol:

There are lots of things I haven't tried on a new cello yet, like the broken heel repair technique of using a threaded fastener to actually put the front of the heel in compression.

Share this post


Link to post
Share on other sites

What do yinz guys think about truss rods in violin/viola/cello necks? 

Wouldn't it be neat to have an adjustable rod that you could torque with a nut right under the fingerboard?  Use a long handled Allen wrenches or something? 

Or would that be under necessary?

Just wondering. 

Share this post


Link to post
Share on other sites
55 minutes ago, Nick Allen said:

What do yinz guys think about truss rods in violin/viola/cello necks? 

Wouldn't it be neat to have an adjustable rod that you could torque with a nut right under the fingerboard?  Use a long handled Allen wrenches or something? 

Or would that be under necessary?

Just wondering. 

I havn't had much of a problem with distortion in that part of the neck, and the little that has occurred could be easily addressed by planing the fingerboard. That's not so easy to do on a fretted guitar. ;)

But I always use maple for the necks, and have had access to really high quality fingerboards, so these factors might have something to do with it.

An adjustable truss rod it might be worth trying though on a cello where bending of that portion was a problem. Most of the bending which results in the neck projection dropping occurs in the heel, which has reduced bending stiffness because it is end-grain, and has much higher overstand than on a guitar.

 

Share this post


Link to post
Share on other sites

In my opinion, the wrench for an adjustable truss rod in a fretted instrument should be thrown away before the customer gets the instrument. Folks trying to fix something by adjusting the truss rod that can't be fixed by adjusting the truss rod. Some of the early Gibson arched top instruments had a truss rod that was adjustable via a bolt at the dovetail end of the joint. Non-user-friendly. I like it.

I started pinning cello necks after the, I beleieve, Strad article, by David Burgess. I have even noticed that violas benefit from it, especially when shipping them to many different climates.

I think that wood movement and the differences in movement or non-movement between the neck and the reinforcement are more of a problem, but hopefully that becomes a problem after we die, and necks are replaceable with a graft if that does happen.

Titanium, I don't know. I'm still OK with dowels and CF.

I get xtra long New Harmony 8 and 10mm endpins and chop them up for reinforcements.

Share this post


Link to post
Share on other sites
7 hours ago, chungviolins said:

Cello neck goes downn bc the cellop top compresses,  not bc the neck/fb bends.

KYC

Koo Young;

I won't argue that compression, deformation and expansion of the plates don't have an affect the neck projection.  I've observed they do... but that does not mean that's the only area that affects projection.  I have a Postiglione 'cello on the bench at the moment in which the deformation of the heel is visible and measurable... and the resulting low neck projection correlates to this movement.

Share this post


Link to post
Share on other sites

Now if it was a titanium nail, that could have some interesting possibilities for really retro design.  :ph34r:

Share this post


Link to post
Share on other sites
7 hours ago, chungviolins said:

Cello neck goes downn bc the cellop top compresses,  not bc the neck/fb bends.

KYC

It is pretty clear that the neck deforms causing the projection to drop.  I had the same discussion with Rene’ back in the day when he had a similar answer to KYC.  The discussion ended when I asked how many mm over measurement do we set a neck graft on cello to allow for projection drop; and then I asked the same question for a neck reset....obviously the answers are not the same.

Share this post


Link to post
Share on other sites

Here's an exaggerated drawing which didn't make it into the article, illustrating the sort of bending in the heel associated with the neck projection dropping (dotted line represents a straigtedge).

Bent%20neck.jpg

Share this post


Link to post
Share on other sites
Thank you all for the replies.
 
I also think as David B. and I prefer to use wooden rods to save restorer's tools (:))and, mainly, to minimize problems related to the expansion/contraction of different materials.
 

I thought about titanium primarily for the best aging characteristics but it is clear that If you mean raw tensile strength, carbon fiber is stronger but in case of unidirectional composite it is stronger in one direction and weaker in the other so, in case of a rod in a heel, titanium may have best bending strength than carbon fiber and may be more efficient to prevent the type of deformation indicated by David in the drawing.

Just thinking out loud, I do not have the engineering ability to make precise calculations in this regard, considering also that the differences could be so small as to be nullified by all the other deformation that cause the lowering of the projection.

By the moment I stick to wooden dowels....

PS To avoid epoxy glue and improve aging I was thinking about a threaded titanium rod screwed into the wood without glue.
 

 

Share this post


Link to post
Share on other sites


Well, I have my own design that helps reduce this {as shown in Davids above diagram} To me this heel weakness comes form using one piece blanks where the neck an heel are cut from the same wood. When we do this the heel naturally introduces a structural weak element based on the grain direction and the dimensions of the heel..

By simply negating this "tradition" , using one piece neck material, and instead making laminated neck blocks where the grain run can be oriented in the "right" {for strength}  direction, I feel my design makes this area much less prone to any distortions as seen above that WILL happen over time.

At first this was done by me to save money by not needing to buy large blanks for cello/guitar necks, but then after time, and doing strength/distortion tests, I came to find that eliminating this "tradition" that seems to be based in no "woodworking logic" dramatically improves the strength and stability by simply exploiting cross lamination and natural inherent strength in grain runs.

 

Share this post


Link to post
Share on other sites
1 hour ago, David Burgess said:

I'm not sure my rather traditionalist customer base would go for visible plywood. ;)

I know you are 100% right, but that does not mean my way is not stronger and less prone to adverse distortion.

Generally the saying goes something like; if 100 people were in a room and only 1 of them thought the sky was blue most times during the day and all the others thought it was plaid, the truth is the sky is blue and the truth is the truth, so regardless of what the others think, they are wrong.

Usually that's where the statement ends,  "the truth is the truth" , but what it doesn't go on to say is if your stuck in a room with a 99 idiots who think the sky is plaid, it's plaid, because the real truth is the stupid low iq mob wins every time  and it doesn't matter what you think even if you're right :lol:

Share this post


Link to post
Share on other sites

I don't think titanium would do better than wood in this aplication.

The dowels work in similar way a non-adjustable truss-rod works in guitar neck but with notable difference that the heel is rather short and thick and the leverage is probably larger than forces in guitar neck. The dowels rely on good grip in the hole, I'd guess not at all rely on bending stiffness of the rods, and I don't think you can get good enough bond between the metal and wood for these forces. Carbon fiber with epoxy would result in better joint than titanium. In this respect I think the weakest part is the Titebond that can slip under tension, but in these applications if the joint is tight and rarely exposed to swings of humidity or (the worst enemy of titebond) high temperatures it can work well enough. I would be tempted to use square rods in tablesaw cuts instead of drilling near neck edges and tapered dowel into reamed hole so I could use hot hide glue without the risk of  premature sticking or forcing the glue into wood.

In long and thin guitar neck straight unglued rod (titanium or CF) that prevents bending can be used (that's how th double-acting rods actually work) but on short heel of cello I don't think it would suffice.

I can imagine something like small trussrod in place of the larger dowel (a'la David B. article) and keeping the other , good anchor down in the heel and washer and nut below fingerboard. If ever the neck drops you could just remove fingerboard and tighten the nut a bit... I believe Bill Halsey made truss rods for his mandolins out of titanium and told me it was pretty tough to cut threads in it...

Few years ago I used something similar in a 12 string guitar with broken neck heel (I was the third guy to have a go at it as the tremendous tension of strings always pulled the crack open) so I decided for a simple fix... (the guitar wos not worth a new neck)... I split-off part of fingerboard between 13th and 12th fret and drilled hole for the largest woodscrew with most aggressive threads I could get in there (that one came from IKEA furniture) I relieved hole in the upper part so the threads did bite just into the bottom part of heel (which I didn't remove from body). When I tightened the screwto check dry fit I could string it without any glue. AFfter I applied glue and tightened the hell out of the screw even the joint closed into decent glue line (considering failed previous attempts). I glued the split off part of the fingerboard back into place so the repair with screw ended undetectable from outside and so far the guitar still works well. I've seen more than few basses with broken neck heels with threaded rod in the heel with one nut  in the back button and other under  fingerboard (ususally hidden under ugly dowel patch). Typically they held well even if the repair was rather ugly....

Share this post


Link to post
Share on other sites

Uh oh Jezzupe, aren't you straying into politics, which we are not supposed to do?  :)

Another version is something like, "Democracy is a lion, a wolf, and sheep voting on what to have for dinner". :lol:

Share this post


Link to post
Share on other sites
13 minutes ago, HoGo said:

I can imagine something like small trussrod in place of the larger dowel (a'la David B. article) and keeping the other , good anchor down in the heel and washer and nut below fingerboard. If ever the neck drops you could just remove fingerboard and tighten the nut a bit...

...I relieved hole in the upper part so the threads did bite just into the bottom part of heel (which I didn't remove from body). When I tightened the screwto check dry fit I could string it without any glue. AFfter I applied glue and tightened the hell out of the screw even the joint closed into decent glue line (considering failed previous attempts). I glued the split off part of the fingerboard back into place so the repair with screw ended undetectable from outside and so far the guitar still works well. I've seen more than few basses with broken neck heels with threaded rod in the heel with one nut  in the back button and other under  fingerboard (ususally hidden under ugly dowel patch). Typically they held well even if the repair was rather ugly....

I tried that on a number of cheap cellos and basses with broken heels, with seemingly good outcomes. Rather than removing the fingerboard, or a portion of the fingerboard though, I just drilled right on through it, reamed the fingerboard portion of the hole with a peg reamer so an old ebony peg could be glued and trimmed to make the hole "go away", sortof, or at least good enough for bass players. :lol:

If I was still doing that stuff, I might experiment with springs (spring washers?) under the head of the screw to reduce what might be a need for periodic tightening of the screw.

Share this post


Link to post
Share on other sites

I know the conversation was centered around cellos and basses, do folks reinforce the heels of violins an violas as well?

-Jim 

Share this post


Link to post
Share on other sites
21 minutes ago, Jim Bress said:

I know the conversation was centered around cellos and basses, do folks reinforce the heels of violins an violas as well?

-Jim 

I do, although I think the value in doing so isn't nearly as clear as it is for cellos.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.