The GPA 902 driver can not be completely tight mounted to the horn flange. It seams that the flange is not as flat as it should be, and a small spring can be seen, maybe 0,2mm.
I am not sure if it is tight around the entrance to the 1inch horn opening and I have not been listening to the driver/horn yet.
However, the original filt gasket on the GPA 902 driver seams not flexible enough to accomodate that distance 0,2mm.
Is there any appropriate gaskets available ? Will some kind of glue around the outer surface of the flange be an alternative ?
Anyone with the same problem? How did you solve it ?
Or is this not any problem ?
Originally Posted by MerlinVSM
- Yes, leaving a gap is a problem .
- Make ( & add ) another gasket ( custom made by you ) utilizing automotive gasket parts ( widely available at "diy" automotive centers ) .
- Look for rubberized/latex cork ( for it's spongy qualities ) .
Another (more difficult) option for fixing the horn….
I have fixed less than perfect flanges by lapping them with a piece of quarter inch glass and sandpaper. Lightly spray glue a sheet of 220 grit (or finer) paper to the glass and stand the horn flange down on top of the paper. Hold the horn by the throat and push and pull across the paper. Go slow and don’t let the horn rock. Patience is the key as you can make matters worse by letting something you are trying to lap rock around. As you work the piece the machined area will grow and you will have no trouble seeing when the flat portion extends all the way around the opening. If it were me, I would stop when the flat portion extends beyond the opening by one quarter inch or so.
Had to look it up for my own education( I wanted to simply call it "grinding" )
LAPPING ( my Saturday morning education ) .
The challenge in lapping will be holding the horn steady as it's massive center of gravity is completely opposite of where you want it.
IMO, if you adhere your abrasive sheet to the glass, use a second piece of glass to "clamp" it so as to avoid any high spots. Also, i'd recommend using a waterproof aluminum oxide abrasive and some lubricant(wd-40 or soapy water is fine).
Personally, i'd find a means of clamping the horn stationary and drawing the glass/abrasive across the flange. This could be done with a large quality file as well. As mentioned above, a steady hand and patience will go a long way. The more slowly you remove material, the more evenly you will do it.
Not all vegetables make good leaders.
I build model airplanes and have, on occasion, had to perform the same procedure on the 1st former of the fuselage where the noseblock sets.
Getting it flat for a good joint is only one issue. Equally as important is getting the thrust line true. Just because it's flat, and all gaps are removed, does not mean the driver will be pointing in the right direction. I'm not sure how critical that is with horns. It's way critical for propellers!
Keeping the flange surface perfectly perpendicular with the horn axis probably isn't too critical with a 511. Consider that just an inch or two into the exponential flare the driver is firing directly into a support pillar and it's welds, dead nuts on axis. Add to that the reflective/directive properties of the vanes in the mouth, having the driver aim a degree or two off axis is likely fairly moot with this horn.
Not all vegetables make good leaders.
Before trying any lapping/grinding I would first determine if I have a problem as the above method can make matters much worse if there is any rocking of the either surface.
Using a Sharpie marker color all around the throat opening on the flange of the horn. Next place a sheet of 220 grit sandpaper on the face of the driver gasket - grit facing out and the driver mounting blots thru the sandpaper. Mount the driver with the sandpaper in place. Tighten the bolts finger tight and rotate the driver back a forth as far as it well go .. do this 5-6 times. The bolt holes are larger than the bolts and will allow a slight bit of rotation of the driver...don't need much. Remove the driver and look around the throat hole ... if the sandpaper scratched/removed the Sharpie marker color all around the hole then the driver is interfacing with the horn just fine and should work fine. Of course if it isn't scratched/removed all around the throat then you will have to revert to on of the above methods but you can try this process to see if you have ground enough off.
This is only ~0.008", so a 'fun foam' or similar gasket is plenty sufficient until the flange's 'bow' exceeds ~1.25 mm:
Creatology
Amazon.com: BLACK FUN FOAM 9" X 12" X 1/16" THICK (12 PCS/PACK): Home & Kitchen
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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