Graupner Small Schottel Repair

[Umi_Ryuzuki]

The Smaller Graupner Schottel drives (#1761) have served
me really well. However the Kort on these drives, mounts over
two pins at the top and bottom of the drive. These are a real
weak point on these drives. I have broken either the bottom or
the top pin twice now on one of these drives. Gluing the piece
back, if you are lucky enough to find, is a temporary fix at best.
The last time I broke the bottom pin, I carved a square
notch out of it's mounting point, and replaced the pin
with a square piece of styrene pinned to the drive proper with
a thin brass wire.

The pumpking pushing while fun puts the propellers at risk of
ingesting those raw stringy pumpkin guts. Since my one of my
drives happend to take the opportunity to do this, I set about
cleaning out the drive by first removing the kort nozzel. However,
when I went to put it back, the top pin had sheared away.
Looking at the drive, it seemed that even a brass pinned piece
of styrene would be under a lot of stress, so this time I milled
away 5/8" of the trailing edge of the drive 1/16" deep. I then
milled a piece of 1/8" diameter rod down to half, drilled it in two
places and silver sloldered in two small pins. The drive was drilled
to match the two pin placements, and the two pieces were epoxied
together.

Hopefully this drive will never break again. :o

[MILLERTIME]

Well done Umi.
I find almost anything out of the box can be improved on.

[Brooks]

Umi, when you make one part stronger, you move the future breakage to another part. If this new "weak link" is easier or cheaper to fix, then you are ahead in the game. You might spend some time, if you have not already, examining the unit to see what the next weak link might be. Or, you may decide to make your own weak link, by modifying (weakening) an existing part that would be easy to replace.

[Umi_Ryuzuki]

I guess we'll see which repair breaks first then.
The brass cored styrene bottom pin, or the
dual pinned brass demi rod... :p

I imagine that to just replace the broken
pins, the entire drive has to be replaced. :(

[toesup]

Are the larger size Schottles from Graupner designed the same way Umi?..

One of mine on 'WW' seems that the bottom mount on the kort is very weak.

[Umi_Ryuzuki]

On the larger schottels The kort nozzle is attached using
screws, so the stresses are different. And no pins to break...
Though I can imagine that over tightening a screw could
split the mounting hole on the top of the kort.

[Prins Willem]

Umi,

Two questions. I have three of these drives and the collar on the lower end of the down shaft is cracked on all three. Have you encountered this problem? Mine are second hand and I don't know their age. i haven't decided what to do about this yet.

Question 2. Did you follow the detailed and explicit instructions for removing the kort nozzle printed on the box?

[Umi_Ryuzuki]

Yes, I removed the drive as directed.

That is a third "z drive" that Graupner makes.
Graupner probably bought the molds from Marx, and
continues to produce this drive as the Graupner #1775.
It is the recommended drive for the Seabex kit.

My first thought to repair that drive is to use some liquid
cement, and bond the crack. And then wrap the shaft tube
with a brass tube/ring. Then work the drive head to fit over
the brass ring and mount as normal.

[bigford]

prins

those are the same as mine with the SAME crack :rolleyes:

[Prins Willem]

I was thinking maybe resin casting the part solid then boring out the center but I'm not sure how that would work. Second idea is to turn the piece out of yellow brass then solder the lugs on. Umi, is the drive you have between the Tito Neri drive and mine in size? That Tito Neri drive is just short of a trolling motor.

[Umi_Ryuzuki]

Maybe casting will work...depends on the hardness of the material you cast.
A brass replacement tube would be nice, but it would take a little work to match up the bearings and mount diameters.

The Graupner #1761 is about the same size. 41mm propeller.
Just a different style of installation. The lower gear box does not detach.

[Shaun Hendricks]

I see an opportunity for a machinist to make some side dough... :D

[CaptLee]

Back in the PAST I had the same problem with the RED Drives(Graupner/Marx) and finally talked to the Hobby Lobby folks they sent my example to graupner and got the replacement part. Hard one did not work as it has to expand and then contract on installation. Have used them up repairing other's drive over the years, but bet they can still get them. These things are a one-shot deal, Thank god you do not need to take them off too often, but order lots as they tend to be needed by everyone.