# General Mandolin Topics > Vintage Instruments >  Gibson Loar Era Snakehead A Jr. Truss Rod...Not!

## Doug Freeman

Seems to be uncertainty in the mando world about whether Loar era snakehead A Jrs have truss rods. Took my '24 along to the dentist's office the other day for a checkup and x-ray. Answer is...no truss rod:

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## MikeEdgerton

I don't believe any of the Jr's had truss rods but you can save yourself the trouble. If a Gibson mandolin doesn't have a truss rod cover it hasn't got a truss rod. Gibson's claim to fame was the adjustable truss rod. Do a quick Google Image search for Gibson A Jr. peghead and you'll see a whole bunch without a cover. I don't know if they ever added a truss rod to the A Jr. line. I've always assumed they didn't.

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## Doug Freeman

Fair assumption, but I've seen at least one authoritative source state outrightly that they do:

http://mandoweb.com/Instruments/Gibs...olin-1924/2083

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## Phil Goodson

Why not contact Mandolin Bros. and ask them how they know?

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## barney 59

First time I ever heard that! Makes me want to remove my fret board to find out. Think a magnet might tell me something?

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## MikeEdgerton

> Fair assumption, but I've seen at least one authoritative source state outrightly that they do:


I'm going to hazard a guess that if Stan x-rays his it will look just like yours but hey, I have an eraser on my pencil and Stan's been wrong before. Not very often but it has happened. 

A rare earth magnet might stick to a mandolin with a truss rod. I'll check my F5G tonight. A normal magnet probably wouldn't be strong enough.

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## Doug Freeman

Good call on the magnet. I just tried it with chunk of neodymium magnet and thin sheet of clear plastic. Sticks convincingly to the back of the neck on a '28 A blacktop (w/ adjustable truss rod, pictured below) but not on a '19 A2 or '24 A Jr.

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## barney 59

I tried the magnet and nothing. I did find the pin that aligns the back to the neck block.

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## MikeEdgerton

I don't think the Jr's had truss rods. That isn't really a bad thing. I've owned Kalamazoo's and other Gibson second lines built in the 30's without truss rods and they all had amazing necks, guitars, mandolins and banjos. If the neck was done right they will stay straight. I have a stack of bad hard drives I keep around just to get the magnets out of them.

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## barney 59

I kind of think that if a mandolin has a straight neck after 80 or more years it isn't going anywhere. The neck on my A-0 is just fine. I bought it in 1971/72 and it was my first mandolin and only mandolin for many years. I used GHS mediums for most of that time and J74's now which seem to me to be just about the exact same thing as the GHS. It's been dragged across the Himalaya been to the jungles of S.E. Asia, Sailed the South Pacific in a 30ft ketch.  Lived with me (and several snakes) in a stone shack in central Australia that got so hot you couldn't touch it and the neck is still perfectly straight. What I trying to say is that it has been through just about every bad climatic situation that everyone says you should never do and it survived! It pretty much looks like it's had as hard life as it has had but it plays and sounds pretty great!

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## MikeEdgerton

I've had Gibson built mandolins from the 30's (no 20's) with no truss rod (the second lines) with great necks. Done right it really isn't an issue.

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## dan in va

i hope the dealers that advertise on this board are reading this, so's there can be some website updating.  i've seen some snakehead and paddle head jr's advertised with non-adjustable truss rods.  But then again, maybe it's possible that some necks were reinforced and some weren't.

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## Bernie Daniel

> Seems to be uncertainty in the mando world about whether Loar era snakehead A Jrs have truss rods. Took my '24 along to the dentist's office the other day for a checkup and x-ray. Answer is...no truss rod:


Are you sure the dentist's x-ray is powerful enough to penetrate wood?  I kind of doubt it? Even if a truss rod were there I don't think you could image it. You need a industrial grade x-ray for that.  

The x-ray a doctor uses for your arm for example will not penetrate bone because if it did you would not see it in the image!   :Smile: 

I don't know for sure but I'll bet dental x-rays are well below 10 KeV? At least I hope they are!  Industrial x-rays are up to 100 keV -- as I recall.  I might be off but a factor of 10?

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## barney 59

What other Gibson instrument had a non adjustable truss rod? Gibson's with truss rods were always adjustable as far as I knew, that was their thing and also their patent. I believe it is possible,even likely, that some older Gibson mandolins had truss rods installed (Martin style) at a later date as a solution to a neck problem but probably not by the Gibson factory. 

X rays at the dentist can see through teeth--teeth are pretty hard at least one would hope so! I just asked my wife -she says that all you would see would be voids and METAL-- She knows that stuff!

Actually once there was this big deal that started when my nephew had an x ray taken for an injured shoulder where he had once had surgery before. There was a bobby pin in the image that the doctors though must have been left there during his previous surgery. It turned out that the only explanation after additional x rays and no bobby pin was that he had to have been laying on a bobby pin when they took the x ray.The bobby pin was behind the bone apparently and still showed up.

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## Doug Freeman

Some years ago I had a 1944 Martin D-18, made during the war effort when they were reputed to have ebony truss rods instead of metal. To confirm it I took it to my dentist (same one, he's also a musician and vintage guitar enthusiast) and we x-rayed it. There was no swath of white going the length of the neck, which would have indicated a steel truss rod, but rather a dark line maybe a quarter inch wide, which was ebony, denser than the mahogany of the neck surrounding it. The dental x-ray setup is plenty strong enough to "see" into wood, which is much less dense than tooth and bone. The x-ray on this A Jr. would have looked about the same whether it was shot from the front of the neck (which it was) or the back. I too think that Gibson only used adjustable truss rods, and that anyone who says otherwise is misspoken.

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## Bernie Daniel

> ....X rays at the dentist can see through teeth--teeth are pretty hard at least one would hope so! I just asked my wife -she says that all you would see would be voids and METAL-- She knows that stuff!...


The dental x-rays go through the teeth?  If so then you would not see the tooth in the x-ray would you?  I do agree you can see a contrast color between the tooth (the enamel, dentine, pulp etc) and the metal so maybe that means partial penetration or maybe just differential defraction. But if the electrons penetrated the tooth the x-ray film behind would also be exposed so you'd have no image?  Its OT anyway - -but now I am a bit confused!   :Smile: 

Edit:  OK I just saw Doug's last post so I'll stop worrying about until the next time I have to have my dental x-rays.

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## dan in va

Different densities of tissue show up on x-ray, depending on the amount of rads used.  If you've ever seen the earliest films, they show great resolution, but today's theory is to use the minimal amount needed.  As for dental films, the question of the rays penetrating bone is answered by being able to see fillings and bone loss due to decay.  This is also seen with displaced fracture reduction using hardware...wires, plates, screws, etc are very clear and distinct from bone.

Another example is that fluid can be seen in lungs as shadows (pulmonary edema, pneumonia, etc) and detail in abdominal images.  If you've ever sat in on radiology grand rounds, you'll hear it said over and over, "If you use your imagination, you'll see here....)"

You're correct about partial penetration, Bernie.  With too much power the image is all white, and with too little power, the image is too dark to see anything.

Now for the truss rod issue:  If the rays didn't penetrate the wood, the frets and strings wouldn't be seen at all.  This film is a good one...note the crispness of the fret and string edges.  It doesn't make any difference if the x-ray was shot from the front or back here.

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## bob marion

until i sold my xray i took a lot of films of instruments.  if you get the values right you can see grain, f holes, bindings, kerfing (different densities of wood, shades of gray) and you can always see metal (absolutely no penetration, complete white).  i'm not going to pop for a digital xray (40k minimum), but that'd be the way to dial in the image.  i put a magnet to two 1918 A's (no truss rods),  a harmony batwing (truss rod),a '30s L50 (truss rod) and a '38 martin O 15 (truss rod) 

its a new hobby, magnets to necks

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## mandroid

2 22 A's  1 plain(A'0') w/o truss Rod, the A4 has one , proclaimed with a Nickel TRC.
 A4 weighs more,  naturally.

 both play fine, have different  tones to them  attributed to what ? I have no clue, I just play 

Could be the aluminum bridge on the A0, but after all this time 
even  experimentally swapping, putting an ebony upper on, made no difference.

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## Doug Freeman

I just took another look at this x-ray and forgot that in fact it was taken from the BACK of the neck--i.e., you can see that the strings sit above the fret. So, clearly the camera was seeing through the entire neck to capture the fret and strings on the opposite side. Were there a truss rod it would read as a wide, bright white line running perpendicular to the fret.

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