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installing 2 way truss rod: is there a wrong way?

Discussion in 'Luthier's Corner' started by Biz, Jan 11, 2006.


  1. Biz

    Biz

    Jan 11, 2006
    Hoping someone with a little insight can help me. I'm installing the 2 way truss rod from the bottom or back of the neck. Is there a wrong way? The rod I’m using is this one: http://www.alliedlutherie.com/truss_rods.htm

    I'm not a physic's major, but it seems if it will go both ways, then there is nothing wrong with placing the round stock towards the fret board, contradicting every picture I’ve seen. Seems logical for a top install to use the flat stock up for gluing considerations, but what about from underneath?

    The reason i would want to do this is to keep the adjustment piece closer to the top because of the totally bizarre shape of the head and string lock of this bass. The neck setup would require removal of the string lock to adjust it and thats not practical. The tuners are on the bridge giving way to an unusual head stock.

    Allied Luthiers, LMI and StewMac have all answered to keep the adjustment side away from fret board...but when asked why? They say just cause.......

    This is a very expensive project with tons of time spent, with no room to experiment.

    any takers?
     
  2. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    SHouldn't make a difference...
    Unless the rotation is inflicted by the touch to the fingerboard, which it should do if the construction is correct (the neck bends forward due to string tension).

    But it shouldn't make much difference! Esp if the rod is covered with some plastic. But, I leave it to you to do the experiment!:D
     
  3. nateo

    nateo Schubie Fan #1

    Mar 2, 2003
    Ottawa, Ontario
    Not to blatantly contradict you, Sub, but I think it'll make a big difference. In my estimation two way truss rods are actually more like 1 1/2 way truss rods. When you compress the threaded portion you can bend the fixed bar quite a ways, helping to correct any bend the strings can cause (within reason, of course). Going the other way, when you expand the threaded portion you can only bend so far before the two rods start to interfere with each other, making it a whole lot more difficult to get more adjustment out of them. Because you almost always use the truss rod to fight the pull of the strings it doesn't have to be able to fight much backbow. Installing it upside down will probably mean you don't have enough truss rod action to properly fight the pull of the strings, while having waaaay too much to fight backbow in your neck.

    Now, I could very well be wrong, but that's the way I sees it. You could try cranking on the rod while it's not installed to see what kind of reverse bend it'll give you.

    -Nate
     
  4. Phil Mastro

    Phil Mastro

    Nov 18, 2004
    Montréal
    Are your truss rods really square on one side and round on the other? The ones I got from there are round on both sides, and they're true double acting. If it really works both ways, i.e. to fix backbow and frontbow (?), you'd be able to use it both ways, but I think it has a bit more adjustment on the side to correct string tension bow.
     
  5. I installed one upside-down once (and only once). It works just fine, does its job like a champ. The downside is this:

    You have to turn it the wrong way to make it work. It's backwards. Righty-loosey, Lefty-tighty.

    Edit: this was a round-round rod.
     
  6. gyancey

    gyancey

    Mar 25, 2002
    Austin, TX
    The same thing will happen with the round-square rod. It will be backwards in comparison to every other installed rod in the universe so eventually someday someone will probably break the truss rod. Also I wouldn't use this rod - I've had a couple of Stew-Mac Hot Rod adjusting nuts break at the weld and now that I see the Allied one is made in China I really wouldn't trust the weld.
     
  7. Rodent

    Rodent Supporting Member Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Regenerate Guitar Works
    I would recommend you take a look at a Sadowsky NYC neck that utilizes a spoke wheel adjustment. If you look carefully, you'll notice that it is installed with the adjustment rod on the top side (against the FB) vs down in the bottom of channel.

    I'm open to correction on this ... but that route for the adjustment wheel would need to be significantly deeper for it to be installed in the bottom of the channel, away from the FB.

    All the best,

    R
     
  8. I say it doesn't make any (noticable) difference on how effective it is, being upside-down. The defining factor there is the difference in length between the two rods. The neck doesn't know whether you made A longer or B shorter, or any combination of those. Only the threads on the adjustable rod know that. As long as they are strong enough (aren't they made of steel), there will be no difference there either.

    The amount of turning on the rod needed to deflect the nut 1/8 inch back (against the strings) shortens the rod about 1/16 inch (rough calculations come close to this). You have a 24 inch rod and a 23-15/16 inch rod. If it's upside down, you have a 24 inch and a 24-1/16 inch rod. That's a .23% total length difference. Does that matter? Hardly.

    But... The backwardsness of it is a bigger issue. Do it the normal way. My backwards one is my personal instrument. If I sold it, I would flip it over first.
     
  9. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    Greg are you using the LMI ones or??????

    Thanks....t
     
  10. Biz

    Biz

    Jan 11, 2006
    yes i tested that, a half revolution =1 1/2 inch either way, but not under a load.

     
  11. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    nateo:
    The amount of length difference will be pretty minor, considering that your first few turns will be to strighten the truss rod out!

    Pale:
    The backwardsness does have an effect on people... But, when you turn right you will notice that you loosen things up, and correct your behaviour. Just make sure it is too loose when you sell it;) :D
     
  12. Rodent

    Rodent Supporting Member Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Regenerate Guitar Works
    Help me understand something ... how is a competent tech or even a complete bass noobie going to mess up a truss rod installed in the less common orientation? You do think one would be checking the results after each 1/4 turn, yes?

    The only people I can see that would have troubles with this adjustment scenario are those who do things purely from past memories of how it was done before and are not paying attention to what they are actually doing in the present ... there's a load of similarities to being in a playing rut here, eh? It's far better to find a tech who has a wealth of experience, but embraces each instrument they receive for work as if it was the first they had ever seen - since each instrument will behave in its own unique way, a good tech will catch on quickly (I say even before a full turn of the truss rod) and you'll have no issues. Only an incompetent tech or a less experienced hack will have any difficulties with a truss rod in the alternate orientation.

    Proof of this theorum: how many spoke wheel equipped Sadowskys have we heard of with truss rods that were broken during set-up???

    In reality the orientation is a non-issue. To be steadfast in the idea that it is a grievous error to install a truss rod in an alternate orientation purely to avoid adjustment confusion is like arguing that the only real bass has four strings because that's what Jaco played, or that the only real bass is an URB, or that the only correct electronics for a bass are passive. Unless there is a true structural reason not to use the alternate orientation for your truss rod - go for it!

    All the best,

    R
     
  13. I'd just be afraid of warranty-type issues. But, I don't plan on selling it. Right now, it's my main bass. It's also my first build, so it's got... um.... character :bassist: . The backwards rod is only one of its unique features. Just saying that I would do it normal-like next time.
     
  14. Biz

    Biz

    Jan 11, 2006
    I bought 12 LMI (2way square+round) they totally rusted before my eyes and when i tested under a real load 2 broke, also the adjustment piece was welded on crooked, some were worse than others but none of 12 were close to straight. I had to give the 1/4 adjustment piece a 3/8 area for the end piece to have room to wobble around. lol Which led to prying without trying.
    Allied's chrome plating is why i like those. That means no rust but at the same time they stress dont "pry" which now has me worried that they also have had welds broke. Which leaves us with the HOT RODS (2way round+round) from stewmac and i think we have a winner. The adjustment piece is actually threaded on the shaft and silver soldiered that means its perfectly straight with the shaft. Another feature is the brass blocks at the ends means no rusting to together. The only boogey man for this one is how much tension is needed to strip the threads in the brass? The only confidence builder in that one is stewmac actually makes this for themselves and no doubt gave it tough testing. The last thing about hot rods are they are taller. (square+round)=3/8 vs. hot rod (round+round)=7/16 But if its the only reliable one, then I'll deal with it.

    gyancey I'm curious which hot rod you had that was welded?
     
  15. Ah, good point. I forgot about that. It is about a half-inch long, so there should plenty of strength anyway.
     
  16. gyancey

    gyancey

    Mar 25, 2002
    Austin, TX
    The 1/8" allen nut one. I use the U-Channel rod now. The spoke nut is probably the best one considering when you adjust the rod you're turning a 24" slightly bent rod under tension. With the U-Channel you're not trying to turn something down the entire length of the neck.