HENRY C. DOBSON 1867 PATENT BANJO

Wow, was I surprised when I got the photos of this piece! Few of you know that in my previous life, I was a professional archaeologist with some involvement in museology. Getting an instrument like this really kicked in my preservation genes. There was no doubt that I would do as little as possible to this banjo beyond making it playable again and stabilizing the condition.

A fellow in New Jersey was looking for someone to repair his old family banjo and found my web site. I got it in the last days of 2011 and worked on it for about 2 months. I returned it in March and recently I was contacted by the owner about a possible sale. If I find the sale value I will put it here.

Anyway, these are very rare banjos. I've seen fewer than half-a-dozen in the past 10 years. A few examples are here:

nice brass-mounted example

museum example

museum example 2

from Gura & Bollman 1999

this one for sale at Musurgia

 

Here is the cover of a banjo tutor from 1882 co-authored by Henry Clay Dobson. Obviously, the image of HC at the opening of this article is taken from this. The whole tutor may be viewed here: http://elib.hamilton.edu/cdm4/document.php?CISOROOT=/spe-ban&CISOPTR=2058&REC=5

 

Henry Clay Dobson (1832-1908), eldest of the five Dobson brothers, patented this rim design in 1867 and got another patent in 1873, No. 136,491, and still another in 1878, which essentially replaces the wooden rings with metal (see for example the Cammeyer banjo here in my web site). Hence, I estimate this banjo to have been built about 1870 +/-3. It has no serial number. There are some pencil marks on the dowel stick but I take these to relate to a batch or mark of the individual craftsman. For its age, it is remarkably original, missing only tuners, bridge, nut, and strings.

Henry's patent is titled simply "Improvement in Banjos." To wit, "it consists in a novel manner of securing the parchment-head to and between two annular rings, which rings are then so attached to the rim of the banjo as to leave an opening or space between them and the banjo-rim for the escape of the sounds produced by the vibrations of the sound-board which is upon the backside of the instrument." (USPTO Patent No. 66810, July 16, 1867).
As we'll see, the present example is very true to the patent illustration. Dobson emphasized that the back - he calls it the soundboard - was important to the tone produced. In modern terminology, this is the resonator. Prior to this, no banjos had a tonewood back.
Here, in this enlarged portion of the cross-section, we see the construction. Basically, there is a wooden rim with a flange at the bottom. The tension hoop attaches to the flange by means of wood screws. A resonator is attached to the flange by L-brackets. In the actual instrument, everything except the screws and brackets are wood.

OK, getting to the actual banjo, here it is as I received it. Note two remnant steel strings, missing 5th peg, relatively recent friction tuning pegs, and plastic nut.
The rim assembly, "pot" in modern colloquial parlance, is complete except for the missing bridge - not a big deal. All of the hardware is present and, as far as I can tell, original.
...and from the treble side. It could be the original head. If not, it is quite old anyway.
The tailpiece is this beautiful, cast brass item. More detailed photos later.
I'm not sure if this is the original tailpiece. If it is, it is attached in a somewhat haphazard way - just a small, ill-fitting wood screw that runs straight into the tension hoop.
Moving on, here's the distinctive early Dobson headstock. It is in remarkably good shape.
On the reverse, we see the unsympathetically fitted aftermarket tuning pegs. These are the simple friction type so popular on tenor banjos for many years. There is a fair amount of honest use ware along the upper margin of the headstock.

At the 5th tuner (missing) hole, we have this lovely carved area which enhances the transition from 4-string to 5-string neck width. The neck is mahogany.

Nice rounded heel with undercut fingerboard. Maker's stamp is on both sides (more later).

 

 Before we move on, I wanted to point out how massive this (and other very old banjos') neck is. It feels like holding the barrel of an old wooden baseball bat. It is 2 1/4" wide and 1 3/4" thick at the 12th fret. Pictured next to it is a neck from the current Saga banjo kit, a fairly typical modern neck.
  - End Part I
   Part II, Taking It Apart
  Oh boy, time to start taking it apart!! First I removed the icky tuners, nut, and tailpiece.
Very pretty tailpiece but no markings at all. Cast brass.
The long screw is just to prop it up for the picture, unrelated to tailpiece.
I started by removing the sheet brass L-brackets held to the outer rim with small brass screws. Only 4 of them attach to the inner rim. There are 21 of them, all present as designed and built. About 1/3 of them are bent but will be easily straightened.
I thought that the inner rim would lift out after the L-brackets were off. Not true! The tension hoop is made of laminated, light wood (probably poplar) with rosewood veneer. I then removed the 20 long wood screws that tension the head. The screws are steel but with very little rust.
With the tensioning screws removed, the tension hoop lifts off easily. The gray color is many years of accumulated dust.

With the tension hoop removed, we see that two steel wood screws attach the rim to the dowel stick.
Then, the rim lifts right out of the resonator. Here you can see the 4 L-brackets that connect the rim to the resonator.
Here's the rim turned over so you can see the bottom side of the flange on the bottom edge of the rim.
Here I've slipped the skin head off of the rim and stacked them in assembly order. The masking tape is simply my reference mark for the tailpiece side of the rim.

Close-up of rim and flange profile. Lots of dust.

The neck attaches to the resonator with two steel screws, a method used a lot in later years.
 The dowel stick plugs into a square hole that does not surface to the outside. No fasteners. Note the thin quarter-round wooden bead around the resonator perimeter. No repairs needed. Photos show before and after cleaning.
  There you are; that's the major structure. Next we'll look at a few other details like the heel stamp, frets, stick markings and so on.
   
 The heel is stamped on both sides with the same stamp. Oddly, it is upside-down on the treble side. It was, for me, hard to photograph well so I am only going to post one of each side here. Some enhancing is obvious.
 Combing the two, it unambiguously reads "Henry C. Dobson's Patent July 16, 1867"
 In trying to tell if these are factory frets, I looked closely at the end of the fingerboard and noted a number of finely scribed lines. I think they were guidelines for more frets but whoever did the fretting stopped at 12.

 

There are lines for 8-9 more frets although the fast few don't seem to be spaced right. It remains a mystery. Sometimes wear on the fingerboard is instructive, but there is none.
There are two pencil marks of the "skin side" of the dowel stick. One may be an initial. The other is pretty clearly the Roman numeral "II".
Some details of the heel cut, just for you wood worker types reading this. Note chisel cuts to perfect the rim fit. Dowel stick is a separate piece of wood although my photography doesn't show it clearly.
Perhaps the oddest thing about the whole instrument is the delicate construction of the tension hoop. It is a very light, soft wood, probably poplar built up of three plys each of four pieces.
Top and sides are covered with rosewood veneer. The red lines show grain direction.
Sadly, the hoop is warped as shown here with the yellow ruler. Its not all that bad.
     
  That's all for documenting the details of this interesting instrument. Next, we'll move along to parts that were damaged.
  -End Part II  
 
Part III, Damages
By far the worst damage is this split in the rim flange as photographed here just as I am beginning to understand it.
Here's a bit better look. The real problem is obscured by the veneer covering the perimeter of the flange.
On close examination, its clear that the upper and lower laminations of the flange have split apart. It appears that there was excessive pressure applied to this one side of the rim, pushing the tensioning screws down into the rim flange to failure.
From the bottom, the delamination is evident and the corner of flange quarter is broken off along the grain.
...and there is a lesser split/break 90 degrees from the major one.
Some of the tension screw holes are stripped out. They were fixed sometime in the past by inserting slivers of wood in the holes. A quick and easy, if temporary, fix.
The outer resonator shell is sound except for some cracks and lifting of the surface ply as marked with red arrows.

 

 

Part IV, Repairs
Its about time! First, I lifted the rim off of the flange. Most of the old glue had let go. Here it is cleaned up, revealing a thin layer of black paint .I think the rim is hickory, reminiscent of grain measure rims. The inside bottom edge has been roughly tapered, probably by hand with a knife. I assume this was done at the factory to refine the rim - flange fit.
Here is the bare flange quarter; the break has been repaired. The rim fits into the groove. Fresh hide glue was used for all repairs. The veneer has been temporarily removed (heat & moisture).
Bottom view of repaired flange quarter. It is light, soft wood, probably poplar.
Just inside the rim is a quarter-round gusset which overlaps the joints of the main flange joints. It glues to both the flange and the rim.

Here we see the reinforcement plates (inner and outer) that overlap the seams of the main flange quarters.
Surely, you're all interested to see the cross-sections. All are poplar.
Here, I'm ready to glue the rim into the 4 flange quarters. It just drops in.
I glued the 4 quarters at one time, clamping the assembly flat and with some circumferential pressure.

Next step is to test fit the inner and out flange reinforcements. There is a little warping but everything fits so loosely that it wasn't a problem.
The head was a bit crooked from slowly complying to the tension hoop warp and the rim-flange break. I really wanted to keep the original head, so I decided to just leave it alone. The tension hoop warp was partly flattened by pressing the hoop between two flat boards and putting it a 150 degree oven for a few hours.
At this point, the tension hoop screws and washers were run through my ultrasonic cleaner, the veneer was re-applied to the flange, and it was all put back together.
Here are still more pics of the rim-flange-tension hoop unit finished. I thought it was better to over-document than under-document.
The neck simply plugs in and is held in place by the two screws. I glued down the loose inner plys in the resonator and set the rim back into the resonator. I had to temporarily remove the tension hoop to get at the dowel stick screw.
Now, here is something odd. The rim tilts down markedly at the tailpiece side. Seems like it must have been level with the resonator upper edge.
To fix this, I made a small "helper block" to sit between the rim flange and the dowel stick. It is not glued in, just pinched between the rim and stick. I put a little stain on it to make it less obvious. On the back, I placed my initials and the date to indicate that this block was part of my repair.
From the outside, its not obtrusive and is easily reversible, so I think it was a satisfactory approach. Rim is all finished now except replacing the tension hoop and screwing the tailpiece in place. Care must be exercised in tensioning the head but it was not a problem.
The first 3 frets were grooved somewhat from the steel strings.
I wasn't expecting them to be bar frets- simple brass rectangular bar stock. I filled the grooves with silver solder, filed them smooth, and reinstalled them. Since I'll be using gut strings, the solder fix should last well enough.
   
  Finally, just a few finishing touches.
   
I selected a set of matching ebony pegs, almost certainly the original set-up. I reamed the holes just enough to clean and smooth them.
Similarly, I fitted a shorter 5th tuner and made up an ebony pip out of scrap.
The headstock didn't really need any work. I made an ebony nut to replace a poorly fitted plastic one.
Here is the pot all done. I used one of those "Minstrel" bridges and gut strings.
The action was very high by modern standards but I think this is close to original. I thought it best to leave it as is.

A beautiful backside.

 
Finally, all finished. It was a great experience.
  Thanks for reading this far!

 

Table of Measurements
overall length 35 3/4"
scale length 25"
resonator outside diameter 13"
rim diameter 9 1/2"
resonator depth 2 5/8"
neck width @ nut 1 7/16"
neck width @ 5th fret 2 1/8"
neck width @ 12th fret 2 1/4"
neck thickness @ nut 15/16"
neck thickness @ 5th fret 1 1/8"
neck thickness @ 12th fret 1 3/4"
neck thickness @ resonator 2 7/8"
fingerboard - headstock angle 21°

 

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