My project french horn was not in that bad of shape. It was a Reynolds that had been worked on in the past. The lacquer was stripped and the horn had some dents. My instructor added to them later so that I could practice! I started working on the horn by getting all of the stuck slides out. It took two days to get all of the slides free. After the slides were out I could chem flush it. The rotors and slides were full of lime and scale
My project french horn
Front of the valves and slide tubes
Back of valves and slide tubes
Chemical Flush
Dirty rotors and bearing plates
Bucket that is ready to go to the chem room
Clean parts after the chem flush
In order to get the slides and rotors clean I had to use muriatic acid. The slides took a couple dips but it was worth it because the lime and scale was removed.
Dent work
Bell stem dents that needed to be removed with the rebound technique
Smashed in finger hook. Common on student instruments
Flat spot in third slide
Another flat spot in the same slide tube
French horn dent work uses a lot of the same dent tools used on trumpet but there are additional tools specialized to the french horn
French horn mandrels that have different curves to fit different bell curves
The attachment balls and cones for the mandrels
Large dent balls for the throat of the french horn
Using the large and small dent balls on a wire to take out dents
A driver that I can attach small dent balls to the end and reach in the slide tubes
The start to taking out deep dents is roughing them out first. I soldered a T handle to the dent and pulled it out using the vice to hold the T handle.
This was a different dent puller I used. It worked nicely for small dents.
I did a lot of hammering and tapping to get the dents out. I used the dent roller on the bell to help relax the bell buckle. The buckle was not that apparent at first besides the out of round throat. As I rolled the bell buckle lines showed up because the bell was trying to relieve the stress from the buckle. Dent work on a french horn is time consuming and some dents can be hard to reach. You have to be creative and a good problem solver to determine what dents are worth going after.
Rotor Repair
When fitting rotor valves there are four things I needed to look at. First, is the bearing plate loose? Second, is there end play in the rotor? Third, is there lateral play in the long spindle? and fourth, is there lateral play in the short spindle. All of these need to be looked at when inspecting the fit of rotors.
I didn't have any loose bearing plates but all of my valves had end play and side play. I worked on the fit of the second rotor. I had to prepare the casing and bearing plate first because there were plier marks creating burrs.
Plier marks on the casing. This is the third casing but the second casing had marks too.
Using sand paper and oil attached to my steel block to sand down the burrs
Once the casing was prepared I inserted a 0.0015" brass shim to the short spindle to get rid of the end play. Once the end play was gone I had to swedge the long spindle.
Large set of swedging collets
Swedging the long spindle
After swedging the rotor was a little stiff so I did some vibrational lapping where I put lapping compound on the long spindle and held the rotor fast while tapping on the long spindle. The vibrations from the tapping moved the abrasive (lapping compound)around the spindle. This finishing step allowed the rotor to move freely but without lateral play
I did get to work on a loose bearing plate on a different horn.
The loose bearing plate and burnishing mount
The bearing plate on the mount in the bench motor
Using a handmade burnisher to burnish the outside of the inner lip
The burnished inner lip. The inner lip is now too big for the casing
So I put the plate back in the mount and filed the lip down so that it would fit 1/3 of the way in the casing
The bearing plate now sits in the casing 1/3 of the way. I tapped the bearing plate in and it fits and cannot be pushed out by hand
Brass Shim
I had to make a brass shim for my third valve outer casing. On the long spindle outer casing there was a corroded hole. On this horn the bearing surface was not effected because there were two layers. I had to make a brass shim to cover the holes and then modified the stop plate to fit over the shim.
Picture of the corroded outer part of the valve spindle
Brass stock that I faced and turned down in the lathe. I had to measure the dimensions of the valve spindle so that I could make the shim to fit. The shim I made was 0.020" thickness
Facing and turning the stock
Using a V drill bit to make the hole in the shim. I then used a cutoff tool to cut the shim to the desired length
Testing the shim over the valve casing spindle
I epoxied the shim to the casing instead of soldering because it was cleaner and I could make sure the shim was exactly where I wanted it to be
I also epoxied a stop plate because the plastic cracked. It was a two part epoxy that dried in a couple hours.
I finished the horn by putting in the rotors and stringing the horn. I hand buffed and used the buffing wheel where I had to clean tinning from solder joints and then finished the bare brass with Flitz
The polished horn I just need to put in the rotors
The bell stem dent work. The dents were rebounded and finished with a steel hammer
The finger hook was taken off, the dents removed, and then the hook was soldered back on
On the third slide I used the dent driver and a hammer. The hard part about slide dent work is the dent ball that fits in the slide tube doesn't always fit through the ferrel that connects the inner slide tube to the slide tube so, the dent cannot be raised completely with a dent ball alone
The second dent in the third slide tube. It is still a little flat but since this area is so hard to reach it will stay like this unless the tubes are unsoldered so that a dent ball can reach the area exactly
The last step is to port the valves, string the horn and adjust the levers
Bumper material can be cork or synthetic. There is also one made of silicone but that is mostly used on tubas or large brass. It depends what the player prefers
Appropriate bumper material fits in the stop plate and allows the valve to port correctly. Cork wears down over time but it can be used for silencing a stop arm on the return
The valve is ported correctly when the marks on the bearing cap and spindle line up
Stringing the horn so that there is the correct amount of string tension can be tricky, but, proper tension and no slop feels great to a player
My finished project!
