Tag: modification

Premier Xylophone Modification (Job No: 1291)


This is déjà vu. Actually I have done it deliberately; sometimes it is nice to work on two identical instruments side by side. However, the job that I have to do is completely different to the other Premier xylophone that I am working on (Job no: 1281). For a start this instrument is almost in one piece!

Unlike the xylophone in Job no: 1281, this instrument lives in cases and is frequently taken out for performances, so portability are versatility are important features that I have to retain in my design solution.

There is often a compromise between weight and strength especially when there is a budget. Unfortunately I do not have the resources or facilities of a Formula One team or Nasa, and I think that most customers would not really want to pay for composite or titanium frames. Aluminium is the option that most manufactures are taking (ignoramacies!). In my view this is the wrong direction; it is like using chocolate to make a tea-pot! Better design is the answer, and accept the fact that percussion instruments are heavy, after all, they are massive. If you want to buy a lightweight aluminium frame that can be carried, then carry it! Don’t put casters on it so that it can be wheeled around. Furthermore, when the aluminium breaks, it is harder to repair. I send aluminium out to be welded; I already spend around £500 a year on renting the bottles of gas I regularly use without needing another one specifically to weld aluminium occasionally.

So I use steel. Steel is strong, steel is cheap, it is easy to work, easy to finish, easy to repair. Steel has a lot of benefits over aluminium, the one downside is that it is heavier. But let’s get our facts right, if I were to hold two bits of tube, one steel, one aluminium, of equal length and equal strength I think that difference between the two would be negligible. Anyway, that’s something for me to find out.

Despite all that, Premier use steel, so that is what I have used to modify this frame. I have also beefed up the design so that the frame is a lot stronger. At the end of the day, it has been given to me because it is broken – the original design failed. Inevitably this means it has put on weight, but I have spent a lot of thought on how to limit it.

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Adams Universal Timpani Problem (part 3) (Job No: 1243)

This post started with Adam’s problems (pt 1).

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So yesterday ended in frustration, meaning that today (yet again) I had to finish off that section of work before doing today’s work.



So the pedal had to be removed several times to be modified and get enough clearance for that nut.  The problem being that I didn’t want to remove that section of the pedal casting completely.

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This drum was the most difficult, which is why I tackled it first.  The other two were more straight forward, but still needed to be checked and tweaks made.
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So the new mechanisms are all in.  They are simple and effective.  The ball joint between both rods is the key, it compensates for any alignment issues between the base casting and the bowl.

Now the new mechanisms are in, the rest of the overhaul can be done which is straight forward on these drums.  After I have finished inverting the drums, the tuning guages can be looked at.  I did have to change the length of the linkage rod between the guages and the fixing point on the central rod because I had moved the fixing point higher up the drum (Obviously I had to shorten them).  What I noticed was excessive wear on the socket joints, so new sockets were fitted.

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Finally all the other rods joined to the spider and the heads can be put on.

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Epilogue.

It is unusual for me to put on clear heads, but interesting because you can see what is going on inside the drum when everything is up and running.  When the customer was collecting the timps, we were setting the heights, and we noticed that the legs foul the rods inside.

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In the photo above in the foreground is the guage with its link rod receding towards the central pull rod which is behind the leg.  Notice how the leg is touching the link rod.

My first thoughts were I had made a mistake, but after looking at each drum individually and thinking about it, I realised that I had inadvertently nearly (but not quite) resolved the issue by moving the central pull rod back and the guage linkage higher.  The mistake I made was the assumption that Adams had made things correctly.  If there is one cardinal sin in my work, it is to assume that things are made correctly.  This of course explains the excessive wear on the guage linkages, obviously whenever the legs are pushed into the bowl, they are bending things out of their way.

All in all, we were not impressed – another schoolboy error by one of the major manufacturers that I have to resolve.  This is why it takes time for me to overhaul timpani, the list of model specific problems that I rectify continually grows!

Adams’ Universal Problem (part 1) (Job No: 1243)

The Adam’s universal timpani are good little drums, the best thing Adam’s make, but they do have one major problem.  The owner of these drums has decided to get me to rectify the problem.  So what is it?
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In a nutshell, when you change pitch with the foot pedal, it doesn’t pull in the centre.

The bowl sits in a cradle that has three legs and a pedal incorporated.  The pedal is a big lever that is attached at the back of the cradle.  The central pull rod is attached to this lever, which becomes a fixed point along the length of that lever.  As the lever moves, that fixed point travels through an arc, not just up and down, so in relation to the centre line of the drum, is moves forwards and backwards.  Furthermore, this fixed point is actually slightly to the front.  Neither of these things is going to give consistent tuning, and is a massive schoolboy error – but just see how many other makes of timps have the same issue, at least this make can be resolved.

In the picture above I am actually recording set up measurements so that the drums get put back together correctly, but it demonstrates the problem perfectly.   I have dropped a rod down the centre line of the drum, and I’m recording how far the spider is pulled by the pedal.  Looking closely, it is clearly visible how far from centre the original fixing point is by the size of the angle between the two rods.

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So what I do is to separate the central pull rod from the pedal by making a secondary linkage, but as you can imagine, it is a little bit more involved than that.  These posts are essentially one days work.

I need to take lots of measurements, which use lots of tools that have been made specifically for the purpose – so many tools that I need to do a job simply are not available.  For instance, below I am measuring how much vertical movement down the centre line I will get on the new mechanism.

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Once all measurements are taken and everything is removed from inside the drum, I can locate the centre of the bowl.

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My design fixes the central pull rod in the centre at the base, and guides it vertically with a guide block.
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The bowl is removed from the cradle and the base casting can be prepared and modified if needed to accommodate the new design.
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Now I can fit the guide block and reinstall the bowl ready to start work on the next stage tomorrow.
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The story continues in Adam’s Problems (pt 2)