Sunday, 30 August 2009

Coarse tuners part 4

Since everything - restringing, tuning and playing - worked fine with the latest version of the coarse tuners, I decided (as mentioned in this post) to keep this layout and cut off the remaining headstock. The shape it has now might be altered slightly - I'm not quite sure about that. I have to paint the headstock black where I've cut and sanded it, but apart from that, I am just going to play it for some time and not alter anything (or not much, at least).

It's a real pleasure to play without the head. Much more compact and manageable.

The P90 neck pickup is just for testing. I'll put the other humbucker back in soon.

Saturday, 8 August 2009

Coarse tuners part 3

As mentioned in this post, I am trying to make a set of coarse tuners, compact and light, for use with my fine tuning bridge, allowing me to ditch the headstock. The first version used T-nuts, but this time, I made a brass plate with threaded holes to hold the tuning pegs. I have also managed to lower my failure rate in drilling holes in the tuner pegs (which are blind screws). Now I am down to around one broken drill bit per finished peg. And I've made twelve of them, six short ones and six long ones. Progress!

It's all mounted on the guitar I use for experiments. And it works. It works well, actually. Stringing up - especially getting and keeping a correct length of the string ends through the peg holes - is a bit troublesome, but I believe that once I've done it a couple of times, it'll be almost as easy as with a traditional set of tuners. The coarse tuning itself is easy. The tuners are sufficiently precise, and the fine tuners of the bridge do the more delicate tuning.

Once I've used the system long enough to believe that it works in the long run as well, I'll cut off the excess headstock and shape the remaining part - plus the brass plate itself - in a more elegant way. I will also tidy up the recessed holes for the allen nuts on the back of the headstock - those are the nuts that fix the peg when the correct note is reached. Plus, I will also buy get some prettier nuts. The ones I used are modified from those that you use for assembling IKEA furniture (Zachary isn't the only one building IKEA guitars ;-) The allen nut on the far left in the picture is for mounting bicycle brakes and I am going to get some more of these.

I also intend to recess the screws that hold the brass plate to the headstock and perhaps some time in the future, I will do a galvanic etching on the brass plate. It seems that I'm not even half way with this small project yet. Meaning that lots of fun remains.

Sunday, 2 August 2009

To-do list - Status

I am having slow progress on the T-beam bass (remember the to-do list?). I have carved out the curves for neck and body on the aluminium beam using hacksaw and file. There is still some filing to do before I mount the mahogany sides, which will also have the same bottom shape as the T-beam.

Time to buy a decent plane and spokeshave.

And to learn to use them.

Friday, 10 July 2009

Coarse Tuners part 2

As described in an earlier post, I've tried to make a compact set of coarse tuners to go with the fine tuners on my Schaller 456 fine tuning bridge, so I could reduce the headstock and loose the big and heavy traditional tuners. The earlier attempt in the form of a locking nut wasn't succesful, but now I think I'm on to something.

I've installed my own coarse tuners, each consisting of a blind screw, a T-nut and an allen nut (a.k.a. an internal wrenching nut). In the blind screw, a hole is drilled for the string to go through, just like the peg of an ordinary tuner.

To tune up the guitar, you turn the blind screw clockwise with an allen key until you reach the approximate tone. Then you fasten it by tightening the allen nut on the back of the headstock. The rest of the tuning is done with the fine tuner at the bridge.

One of the beautiful things about it is that when you tighten or loosen the string by turning the set screw, the height of the string over the fingerborad stays the same, since it rests in the screw's thread. And the pull of the string tightens the allen nut against the T-nut, securing the string even more.

The best thing about it is, it seems to work perfectly. And it's much smaller and lighter than ordinary tuners, so it's a good solution if you want to build a headless guitar - or convert an existing guitar to one. You'll have to leave a little bit of headstock for the T-nuts, but that's not much. And you might want it anyway to stop your fretting hand from sliding off the neck.

On my own guitar I've mounted the tuners on the very end of the headstock. The reason is that I'll be using the other sections of the headstock for experimentation with alternatives to the T-nuts. A set of threaded inserts and a brass plate with threaded holes are some of the things I want to try. Next experiment will probably be threaded inserts mounted on the next section of the headstock. And I imagine that when I have reached the last section of the headstock, next to the nut, I'll know which of the solutions I prefer.

Drilling the string holes in the blind screws was a pain. I only got two made before I had dulled or broken my drill bits. I'll have to buy some new ones and do it right. That's the reason why the remaining four strings in the picture go to traditional tuners.

Btw, I imagine that if you add some loctite or similar to increase friction, you might be able to do away with the allen nut. Afaik, there also is a substance called "peg dope". I have to get some and try if the tuner can hold the string without the allen nut.

Thursday, 4 June 2009

To-do list

Nothing much has happened on my T-beam-bass lately. I've replaced the jack connector since the old one didn't work and clamped the connecting cable going from the jack more securely to the sliding bracket. Plus, I've borrowed a friend's bass to do some comparisons of sound, feel and ergonomics.

His is a 34" bass, and though the picture doesn't really show it, mine, with its 30" scale length, is much smaller and lighter.

My bass still isn't exactly pretty, but I do intend it to be so one day. But until now (and probably some time ahead as well), most of my focus is on experimentation rather than looks.

Nevertheless, in an attempt to convey an idea of what I expect it to become some day, here's a list of some of the things, I'd like to do next:

  • Make the saddles lengthwise adjustable for intonation, i.e. making slots for the saddles and fastening them with nuts.
  • Shape the neck as shown on the image . I have to modify the sole plate of my jigsaw to be able to do that.
  • Make a prettier and more ergonomic shield in 5 mm acrylic (that's approximately 0.2"). The current one is just 3 mm thick, and it's too fragile and flimsy looking.
  • Make mahogany sides rather than the current spruce ones. What's keeping me back here is that I'm not quite sure yet where the holes for the shield are going to be, and I'd rather keep the mahogany intact and experiment on the spruce.
  • Decide whether I like the sound of the vertical pickup. If so, I'll tidy up the bracket. If not, I'll buy a P-bass-pickup and use one half of that in a new bracket.

Friday, 8 May 2009

I am not alone

One of the good things about the T-beam bass or guitar is that it's fairly easy to build a functioning instrument and improve it from there. In spite of its relative simplicity, there's still lots of challenges in it. If you're ambitious, there's plenty of aspects to improve. If you're not, there's still the joy of building your own functioning, albeit crude instrument.

It's a really good project in many ways, but until recently, I thought I was the only one making a T-beam bass.

To my delight, as I discovered here, I am not the only one. Kaspar Torn is building one as well. It's still in its early stages, and so far, it looks very promising. As you can see from the pictures, it differs from my own project in a number of ways:

Strings are anchored in a bolt through the vertical flange

String slots and zero fret

Tuners upside down

Angled tuners

This project is going to be interesting to follow. Kaspar leaves many options open, such as a detachable acoustic body and a spike, allowing it to be played upright.

I will post updates as the project moves along.

Tuesday, 5 May 2009

A slightly prettier sliding bracket

I've made a sliding bracket for the small pickup. It slides with little effort and easily picks up the different antinodes of the strings. Unfortunately, the pickup itself doesn't sound that good, so one of the next steps might be mounting one half of a P-bass pickup in a similar bracket - or perhaps have two sliding brackets and the usual switching arrangement.

Trying a good, well-known pickup should give me an idea of what the instrument sounds like and make it easier to find out its particular characteristics.

The system of cable and female jack on the body also works fine. I plan to add tone and volume pots down by the jack at some point.

Saturday, 4 April 2009

A body that preserves vibration

With the addition of a body to the T-beam bass, it begins to resemble an instrument.

The body is a 3 mm (around 1/8") acrylic (or plexiglass) shield, cut with a saw and an angle grinder, polished, and bent in shape with a hot air gun. As with almost everything else on the bass, it is not intended as the final version. For this, I will use thicker (probably 5 mm) acrylic sheet and have the leg rest further to the back.

The acrylic shield is slightly bowl-shaped so it follows the contours of my body. It's a fairly deep bowl shape ;-) It has a leg rest bent into the lower part and an arm rest created by folding back a wing on the upper part. It quite looks like the body of an Ovation Breadwinner, though that was not the intention originally. It's very comfortable, and I expect it to be even more so when I've moved back the leg rest.

The four mounting supports that connect the shield to the stick will have to be replaced with a central support mounted on one of the two places where the stick has least vibration. A so-called node. I located the node by suspending the stick on two springy foam blocks, pouring salt on the stick and tapping it with a knife handle. As predicted in the marimba literature, the salt would gather to show the location of the node. Luckily, the node is somewhere in between the mounting supports, which makes construction easy. BTW; marimba and vibraphone builders do a lot of interesting research into the acoustics and vibration of wood; something that the guitar builders might draw upon in their work.

The reason for having the shield mounts on the node is to preserve vibration in the stick and not have it travel through the body and into the all-absorbing torso of the player. The node does not vibrate - or at least it vibrates less than other areas of the stick, meaning that less vibrations will be transferred from this point to the shield than from any other areas. I expect it to have a pronounced effect on sustain, and perhaps also on tone.

Some sort of leaf spring suspension mount might give even better isolation between the shield and the stick, but that will have to wait for a later version.

Thursday, 19 March 2009

A sliding pickup

There has been several attempts - by for example Westone and more recently Norton Guitars - to make a pickup that can be moved to the areas of the strings where different antinodes and their corresponding overtones are located. This gives you the sound of a neck pickup, a bridge pickup and everything in between. Though only one at a time.

The T-beam bass and the bracket for the humbucker pickup were too obvious a candidate to not trying something like this. And since I allow myself an impulsive and unstructured approach to my hobbies, I gave it a try.

The pickup bracket has nylon cable clips screwed to it. The clips grip the edge of the T-beam top flange and allows the whole thing to be slid easily along the beam. It was necessary to isolate the pickup from the vibrations of the guitar body (hence the rubber bands and foam padding). If not, the vibration characteristics of the string on the pickup's location would be hardly audible compared to the much stronger body vibrations also received by the pickup. Isolating the pickup also significantly reduced the noise of the nylon clips sliding along the T-beam... nice, because now it is possible to slide the pickup "in-tone" and hear the subtle changes of the timbre of the string.

The bracket and pickup is big and heavy, so one of the next steps will be making a sliding bracket for the much smaller between-strings pickup, which I made earlier. The small pickup should also be better at sensing a small section of the string, where the humbucker due to its length picks up a lot of vibrations - including the unwanted ones. With the big pickup, you can easily hear the difference up and down the strings, but the effect isn't exactly striking. I hope and believe that the small one will do a better job.

I had to rout a channel in the wooden sides for the nylon clips. With everything on, in the afternoon sun, it looks like this:

Thursday, 5 March 2009

A vertical pickup

I made a pickup that sits vertically between the strings. Since the bass is two stringed, the pickup picks up one string from each side. It works well, but I have to keep it towards the bridge end, otherwise the strings will hit it.

It is made from an acrylic sewing machine bobbin wound (on a sewing machine) with a very thin copper wire: 0,05 mm which is somewhere in the neighbourhood of AWG44. This wire is thin as human hair and very prone to snapping... it happened more than once, but I've learned to handle the delicate wire.

I measured the DC resistance to 2,3 Kilo Ohm. I'm not sure how much I can deduct about its impedance from that information, but it's only around one fourth of the resistance of the humbucker that I used earlier.

The center of the bobbin contains a stack of small neodymium magnet discs and iron cylinders. This allows me to vary the magnetic force by replacing an iron disc with a magnet if I want it stronger - and vice versa, of course.

I can rest my hand on the pickup while playing, but sometimes it's in my way. Still, I usually find my way around it and I really like the simplicity of having one small coil picking up both strings. I might recess it a bit into the aluminium and I might abandon it in favour of a more traditional pickup, but overall, I'm quite satisfied.

BTW, I also made two tuning screws from ordinary screws fixed in oak dowels with epoxy glue. They have just adequate friction against the fingers, but they'll have to do until I get a couple of knurled nuts. Still, compared to using a screwdriver when tuning, it's a great improvement.

Thursday, 12 February 2009

Using traditional tuners for headless designs

A post on this blog contains some nice sketches of headless guitars with traditional tuners mounted behind the bridge. Some designs even had holes through the body for the tuners. That looked good, but it might be difficult to get a good hold of the tuners unless the holes are very big. Since tuner systems for headless guitars are few and expensive, using the old-fashioned ones in new ways is a viable alternative.

It struck me that a possible solution could be to mount the tuners on a metal plate in a hole routed through the guitar, the tuner knobs sticking up through the plate and the strings going through slots in the plate. I've fiddled around with designs like that before (only on paper so far), but in this particular case, with a tune-o-matic bridge, it seems especially straightforward.

On one of the sketches on the blog, it would look like this. Sorry about the artistic quality, the picture only serves to explain the idea.

I couldn't attach images to my reply on that post, so instead i put it here. Anyway, it shouldn't all be about T-beam guitars.

Monday, 9 February 2009

A magnetic pickup

Previously, I've talked much about piezo pickups. I had great expectations to piezo discs, because they would give me more freedom in construction, since I would avoid having to make room for traditional magnetic pickups. I still have expectations, but so far, I've not been successful in making or buying a suitable pre-amplifier. I've tried a couple of designs, but none have sounded very good so far.

For the sake of my own motivation, I took a little detour from the piezos and put a guitar humbucker on top of the strings. The distance between the two rows of pole pieces is 18 mm - exactly the distance of my strings. This makes it possible to mount it lengthwise over the strings. It gives acceptable sound, but the mounting bracket doesn't integrate well with the overall design idea of having a sleek stick for a bass.

On the other hand, it _does_ have a certain rustic honesty about it. And most important: now I can play the bass and get a decent tone, while I figure out if the neck should be a little thinner, rounder or narrower. As well as many other things.

Tuesday, 3 February 2009

Wooden sides

I made two wooden sides from some spruce, just to test how it worked. Also to avoid messing up my good mahogany plank with early mistakes. I routed the cavities for saddles, nuts, strings and tuners with an ordinary plunge router in a table. I have little experience routing, but the cavities do what they're supposed to.

I've tried to make the sides fit tight against the top flange by having the holes in the vertical flange just a tad higher than those in the wood. This way, when I screw it together, the screw tightens the wood sides towards one another as well as lifting them against the top flange. It works ok... if you see gaps, it's because the wooden sides are made quick'n'dirtily, not because there's something wrong with the principle itself ;-)

I'll be sticking with the spruce sides for a while. There's a lot of things that I am yet going to try out - and which will need holes drilled in the wood. The mahogany sides will have to wait until I've settled on a final design. This especially includes whether to make the neck thinner. It feels a bit too thick even for my big hands, so I might slim it down from 4 to 3,5 cm (that's from 1.6 to 1.4 inches). That will still be much thicker than a traditional bass neck.

Thursday, 22 January 2009

New tuners

I've always wanted to try out my a particular form of tuners for headless guitars and basses. They work by having a scew pulling a brass block in which the ball end of the string is mounted. The main inspiration was Jeff Turpin's tuners; drawings and building guide for similar tuners can be seen at ScottyD's home made tuners. But since I have a T-beam, I can do away with the housings for the brass blocks that these designs use, and rather let them slide on the underside of the T-beam like this:

Two of the screws are for holding the brass plate on to the T-beam
The other two are for tuning.

I thought that 'd give it a try since I was going to cut the T-beam to length and I needed a bit of room for the tuners, so it was the last opportunity to try it out. It works very well - very smooth and precise, so I'll stick with them rather than reverting to the traditional tuners. I believe they'll be even better when I've mounted hex socket screws so I won't have to use a screwdriver to tune them. The holes where the strings go through the top flange could use some lengthening as well, which would make the strings' movement easier.

The picture shows the sharp turn, which the cable has to do going through the flange.

I'll stick with the new tuners rather than the standard bass tuners it had on earlier. That will also make it easier to make some good looking wood sides for the T-beam since I won't have to worry about making room for tuners that stick out. The brass blocks and string ends will be hidden within the body.

Earlier, while the traditional tuners were still on the bass, I was making and mounting a string tree that I needed for them. Unfortunately, the aluminium is so soft and sticky, that I broke off one of my threading taps inside the T-beam. Trying to get it out by cutting room around it with a dremel only made things worse. I'm afraid that I'll have to stray from my "form follows function" principle and make some sort of ornament to cover the damage, now that I don't need the string tree any longer.

Headstock-end with damage from string tree mounting attempt
(I later turned the T-beam around so this end was the bridge end back then).

On the image above, btw, you can see the strings going through the flange. They are secured on the underside by cable stops - the type used e.g. for brakes on mopeds.

Next step will be making the wooden sides plus some experimentation with Piezo pickup pre-amplifiers. And then back to tidy up the T-beam. Later, I am thinking about making a detachable body from steam bent plywood.