1930s Electronic Metronome Restoration

Greetings friends,

Recently, I lucked out and received a very cool vintage metronome from someone in my local "Buy-Nothing" group. As some of you know, music is a big part of my life and I was very excited about this find and at the prospect of restoring it to fully-functioning condition.

Let's start with a little bit of history on this device, since it has some cool design features and is one of the first electronic metronomes to hit the market. The Franz electromechanic metronome was invented in 1938, and saw production through 1994. The mechanism by which the metronome operates is very interesting in that it uses a synchronous motor to spin a wheel which drives a shaft containing a ledged cam lobe (not sure what else to call it?), which on each rotation strikes a spring-loaded hammer onto the interior wall of the metronome box. Changing the angle of the wheel with respect to the motor spindle by way of the external dial ("selecting the tempo") changes the frequency of the hammer strikes.

The metronome I received was in fairly good condition, but with a fair amount of dirt on the exterior. The mechanism worked well at higher tempi (80+ bpm) but was very irregular at slower tempi. The bottom plate, seen above, is in good enough condition that I won't be altering anything about it during this restoration. I'm happy that the label is legible, so I won't try risking any damage to it by trying to clean it. I'll just have to live with the small amount of rust.

To start the restoration, I disassembled the entire mechanism and right away cut the old power cord which was very brittle and starting to crack in some places. I bought a cheap 8-foot extension cord to re-purpose as the power cord for the metronome. The socket is interestingly designed, and it's plenty obvious how the cord connects. The other end gets soldered to the switch and motor, which we'll see later. 

To clean the exterior, I started off with simple dishsoap and warm water, and used an old toothbrush to get into the dirty crevices. Since the white lettering was oxidized and already chipping out a bit, I decided to just scrub until all the letters were cleaned out. With all the dirt removed the appearance of the case was already hugely improved, but I decided to polish a little bit using rubbing compound just to give it a little bit of shine.

The mechanism itself was quite clean and didn't require a whole lot of manipulation, though I did need to make some adjustments to make the slow tempi more consistent. I noticed that at the lower settings the wheel that operates the hammer was not making full contact with the motor spindle. To fix this I simply cut some pieces of thin leather to act as shims, which lowered the height of the motor and allowed the hammer wheel to make full contact across the full tempo range.

I used a lacquer-stik to fill in the numbers on the face on the metronome as well as the "ELECTRONOME" lettering underneath the dial (although these didn't seem to be filled when I received it). The metal indicator on the dial was polished using Brasso, and the reassembly went without a hitch.

Fully functional again, the metronome has a permanent place on my piano. I use it occasionally, especially when showing off to guests. After 80 years of use, it's great to see some new life in this metronome!

Thanks for reading,

Juju

References:

1. http://www.franzmfg.com/history.htm

BMW R65 Restoration - Part 6 - Handle Bars, Carburetors, Chokes, and Throttle

Greetings friends,

This is a continuation of my series of posts documenting the restoration of my BMW R65. For the previous post in this series, click here.

Today we're going to jam a lot of small steps into a single blog post. In the last post I mounted the engine and transmission into the frame of the bike, and today we're attaching most of the peripheral equipment that the engine needs to run.

Let's start with the carburetors. These guys were in pretty good shape, and as far as attaching them to the engine, they were surprisingly easy, as there's a rubber sleeve that clamps onto the carb, connecting it into the intake of the corresponding cylinder. The backside of the carbs have fittings to allow the throttle cables and choke cables to be attached, and a small hose barb for the fuel line. We'll touch on each of these as each is installed. As part of the restoration/modification of this bike, I'm going for somewhat of a "Cafe Racer" style, which commonly uses pod-type filters on the carburetor inlets, which can be seen below. The filters mounted with a rubber sleeve exactly how the carbs mount to the cylinder.

The airbox that came with these bikes was pretty ugly in my opinion, so at least for now I'm forgoing trying to find a used airbox and simply eliminating it for the individual filters, and covering the top of the engine/starter motor with a nice cover. There is much debate in the community surrounding the impact on the engine of pod-filters vs airboxes, but for the sake of simplicity this is what I'm doing for now.

Pod filters fit right onto the carbs!

This motorcycle was originally equipped with choke cables that were manipulated with a knob mounted on the handlebars, but for an overall cleaner as less-cluttered look, I decided to forgo the cables and use "Choke Pull Tabs" instead. These tabs are thin wires connected to aluminum knobs that attach directly to the carburetor and allow fast choke (dis)engagement. The only disadvantage to the tabs is that each one needs to be pulled by itself, whereas the original choke cables would have pulled both chokes simultaneously. This isn't an issue since it's quite easy to stop for a sec and pull them to disable the choke.

It's obvious where to pull, right?

The handlebars I'm installing are unpainted stainless steel, as close in dimensions as I could get to the originals (22 mm dia.). They bolted on very easily, so there's not too much to discuss surrounding their installation.

The throttle body was a relatively cheap amazon purchase, and was a very simple fit over the end of the handlebar. The rounded end caps of the handlebar are tack-welded on, so I had to grind that back a bit to accommodate the throttle body. I lubricated the throttle body with the green grease I used for the steering bearing in a previous post. 

I purchased a throttle cable kit, which included all the necessary fittings to cut to length and assemble my own throttle cables. Using the old throttle cables as a reference, I cut the wires to length and assembled them in the same manner as the old ones. The old cables use a splitting assembly to allow one cable from the throttle body to control both butterfly valves at once. The kit I bought included this splitter, so I was able to recreate the original cables almost exactly.

   

Completed throttle cables. I forgot to take a pic of the
originals before I disassembled them...

Once the cables were fully assembled, routing them from the throttle body through the frame was simple, and the cable ends slipped nicely into the provided throttle levers on the carburetors. The levers are tucked away behind the carbs, but I'll include a picture in a different post to show them.

A little too zoomed-out, but here you can see the starter cover/airbox eliminator.

The handlebar grips were very easy to install thanks to a pro-tip from a friend of mine. Wetting the inside of the grip and the handlebar with isopropyl alcohol (IPA) allowed the grips to slide on very easily, and after the IPA evaporated overnight, the grips were super solidly in place. I did the same thing for the footrests!

There are a number of other accessories that will ultimately bolt onto the handle bars, but I think those will best be covered in a separate post. The engine electrics will also be covered separately, so for now, that's all!

Thanks for reading,

Juju

P.S. For the attentive readers in my audience, yes there are components installed on the bike that haven't been covered by this series of posts. I work on the bike as I go, and select parts to write about, but those don't always match chronologically...

Maple Slab Coffee Table - Part 2

Greetings friends,

This is the second and final part of the construction of my maple coffee table. You can view part one of this project here.

Onwards...

When we left off, the table was waiting to finish drying before a few final passes with the router to finish the top. After reading some articles online, I found that likely the slab had been sufficiently dry for some time. Apparently endgrain slabs can dry 15 TIMES FASTER than their cross-grain counterparts.¹ With no doubt in my mind, I was ready to flatten out the slab to it's final dimension.

With the same setup as before, my brother and I chipped away at the slab, and after a few hours had the top surface leveled off and looking pretty. As I had mentioned before, the whole slab had cupped slightly, so all outside edges were higher than the middle when we were flattening it. Two passes with the router and it was done! I'm so glad that the ugly gouge is gone!

Just about to get rid of the gouge...

Finished! Woohoo!

We flipped it over and decided (in order to preserve the thickness of the slab) to flatten the bottom only enough to accommodate the stand/legs that the table will sit on. If we had gone until the bottom gouge was removed, the resulting slab may have only been an inch or so thick!!! We took a belt sander to both sides of the slab to level out the router marks, and called it a day. Not bad looking for a few hours work!

At this point the long sanding process began. The slab has some lovely figuring that I wanted to showcase, and I knew that I would want to sand to at least 600 grit before applying any kind of finish. I started with 40 grit on the random orbit sander (ROS) to remove all the scratches left by the belt sander, which ended up taking the bulk of the total sanding time. Once I was satisfied at 40 grit, I gradually worked my way up the other grits until I was satisfied with the look of the figuring. I would periodically wipe on a thin layer of shellac (1# cut) to check how the figuring looked before moving on to the higher grits.

That's about as far as I got..

Once the PNW weather started turning toward the wet season, I decided to attach legs to the slab and put it into use. It may be a while before I actually before finish sanding the surface, especially since it's finding so much use as our living room table. Here's a picture of it's current state, and I'll update this post later on if and when I complete it! 

Frankly, I'm really happy with how this came together, and the finishing touches will be completed whenever there's time. I'm not holding my breath.... 😁

Thanks for reading,

Juju



1. Reeb, J. E. Drying Wood. (1992).