Tag: overhaul

Adams Marimba Tuning (Job No: 1069)

A west end show is going on tour and they have a marimba tuning problem; the marimba is tuned to A440Hz, but the musical samples are recorded at A442Hz. So the notes have come to me for re-tuning.
During the first cycle of tuning, I make a record of where the notes are presently, the results are below.


In the graph, the two smooth lines represent what the tuning should be, and where I need to raise the pitch to. The wiggly lines show that the tuning of the notes is actually all over the place.
The biggest problem area is the third partial which is consistently flat.

In simple terms, to raise the pitch, the note needs to be shortened in length, removing material in the centre of the note increases the flexibility of the bar, which lowers the pitch. It is harder to raise the pitch than to lower it, furthermore, shortening the length affects all the longitudinal harmonics, whereas harmonics can be somewhat targeted when tuning down.

Therefore, I raised the pitch of these notes so that all the harmonics were at, or above the target pitch, then the harmonics that were sharp were brought down into tune.

1″ Chimes (Job No: 1063)

I think these are Viscount chimes, in for repair. The damper pedal doesn’t work, and there are missing parts; also one of the bells is missing a cap, and the whole frame needs a bit of TLC.
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The first thing I ask when I receive a broken instrument is, why did it break? In this case, it looks likely that the missing part snapped, but why? Probably because the design wasn’t that good to begin with, and that the force needed to damp the bells was too great for the aluminium that the part would have been made from.
Therefore, I need to re-design the part, and look at the damper bars to improve their effectiveness, and subsequently reduce the force needed at the foot pedal.

This is the new part I am making


New component made, now it moves in two directions; forward and back, left to right to ensure that the tension force is all inline and there is no twisting. Part made from steel for strength.


Measurements of the bell cap taken off a complete bell and a copy made:


The bell is keyed to both provide a clean surface and give the solder a surface to stick to:


The cap can now be soldered in.

Ross Vibraphone (Job No: 1064)


This vibe is in to fix a motor problem, however there are more problems; broken note rail, and a dreadful repair that someone has done to the frame which means that the diagonal braces don’t even reach the connection socket

Plus welding commonly known as “bird shit” which aptly describes its appearance and strength. What is more, whoever did it left sharp bits of spatter, and a sooty mess.

The electrical side:
The first problem is in the plug, the fuse is loose in its holder, the sort of problem that starts fires. Secondly, despite the speed control being housed in a metal box, there is no earth cable. I’m not an electrician, but I thought that this was illegal, common sense dictates that an earth connection would be a good idea, and the motor manufacturer does use an earth wire in their controllers.
Finally, the wiring in the mains connector to the circuit board is not soldered, so those wires could have come out at any point to make the casing live.
Whoever repaired this instrument before shouldn’t be trading!


The Frame Repair

I started by cutting away the bad repair to leave the two legs ready for a fixing bracket to be made.

At the same time I have to make a new square bush that prevents the leg from wobbling.

Then the completed legs were assembled, the frame jury rigged into position, so that the new bottom bar can be cut at the correct length.

Over the years I have done this countless times. My design has evolved, but the basics remain; the frame is the structural element, built to withstand the rigours of use. The keyboard bed just sits on top. The reason is simple – its more expensive to repair the keyboard bed.

Once the bottom bar is fitted, and the rest of the frame components made, everything is assembled ready for welding.


Finally I need to make a new rod to connect the damper to the pedal, to replace the sorry example that was on the instrument.


Job Completed
Here is the finished article; new base frame, new motor and controller, new damping mechanism.

Premier Timpani (Job No: 1062)

A set of 3 Premier fibreglass concert timpani to be over hauled. The usual problem with Premiers – the bowl shifts in the chassis. This is a bad example where the bowl is actually being pulled into the inside of the suspension hoop. These types of issues will affect the tonality across the playing range but one part of the range may well be in tune.


Counter Hoop

Cleaning of the old, incorrect, counter hoop felt and glue residues ready to be replaced correctly. First the hoops will be checked for loose parts and that they are flat and round. After final clean, new felt will be inserted. The counterhoop is like the nut on a string instrument, bad implementation will create a vagueness in the note.

The counter hoop (above) is not flat. This is a universal problem with counter hoops. In application they bend down at the tension bolts, this means that the tension being applied to the drum head between the bolts is less than at the bolts. The bearing edge or rim of the bowl in acoustic terms is a nodal point, where the amplitude of a sound wave is zero. The centre is an antinode, where the amplitude of the sound wave is greatest. In order to achieve a harmonic note in a membrane (drum head), the nodal point needs to be round. Therefore, the effects of the counter hoop flex can best be visualised in the diagram below:

The variation in tension has created a wiggly edge to the nodal point. This creates problems when putting on a head and clearing it (removing overtones).
The distortion can be minimised, but I have yet to definitively solve the problem, only achieving up to 1/2mm out of flat depending on where the hoop has bent.

Pedal action:

Pedal casting dressed & nylon inserts reamed so that the pedal fulcrum spacer can be gripped firmly between the pedal arms without inhibiting the pedal movement.
The fork pressing cleaned, lubricated and the fork casting dressed to ensure squeak free smooth operation.
The adjustment screw barrel nut tapped, de-burred and lubricated to ensure easy adjustment and smooth movement.
All three elements allow the pedal to operate without resistance; the pedal return pressure is provided by one spring inside the clutch mechanism.

Pedal mechanism:

All the work here is aimed at making the pedal operation smooth and resistance free, and to enable the whole assembly to be stiffened. Therefore decreasing friction in the vertical operating movement whilst minimising horizontal play.
My aim is to improve feeling whilst playing, assist the function of the clutch mechanism and facilitate greater accuracy in instrument set up which in turn improves quality of tone.


New aluminium shoes have been welded onto the foot of the base casting, and now the chassis are ready to be cleaned and painted. As the drums are moved, the casting wears down which lowers the front to the point where the pedal mechanism fouls the floor. Screwing on a plastic pad is a temporary fix, but the problem is that the force applied to the pad is shear, and that is the weakest aspect of a screw. Once the screw has snapped, your left with removing hard steel from soft aluminium.
After the chassis have been worked on, and the set up done, everything is ready for reassembly.
Job complete

1″ Chimes (Job No: 1026)


I have been commissioned to make a set of replica 1″ Chimes to replace a set that has been damaged.
Having taken delivery of a load of brass tube and solid round, I need to cut the tubes oversize to clear the workshop floor & prevent the tubes from being damaged.
Once the tubes have been cut and de-burred the hanging holes are drilled. The holes are then chamfered and filed to remove any sharp edges.

The caps made next, turned to a sliding fit:

Then cut to length, and the edges cut to a 2mm radius to match the bells I’m replicating.

The caps and tubes are soldered in, cleaned up ready to be polished and chrome plated.


Frame Repair
The frame has two issues; the damper mechanism has broken, and a leg is bent

The two pins that make the fulcrum for the damper bar were held in with two tiny pins.

Due to the fact that both are missing, the design is flawed. I will replace them with turned bolts that can be thread locked and tightened hard into the frame.