Yamaha GH1

[Roger Jolly]

Hi Ron.
           The plate was secure on the inner rim, when the outer rim let
go, it was enough to let the plate flex up ward. a.k.a. the two rims are
needed to hold the tension on the plate.
One of the dangers, of thin two piece select hardwood rims.  One of the
reasons we use nose bolts in the killer octave area is to stabalize the
plate.  The GH1's  are not secured to the beam as in other models.
Incidently the same problem exist in the obsolete Baldwin model's C and B.
It is a major contributing factor in the stability of tuning in this register.
The unit I repaired was worked on thus;  
1. Plate removed.
2. Blocks were made up so we could clamp the elevation of the inner rim to
the outer rim.
They were flush on the bottom.
3. A variety of clamps and cauls were made up to clamp the rims together.
4. Piano placed upside down on the floor, to run in enough epoxy into the
seperation..
5. Piano placed on it side and all clamps tightened.
6. After 24hrs curing dowels inserted.

I would have added a nose bolt for the plate, but alas no beam in the right
position.

Bearing was restored.

Redesigning the Baldwin B, (now Chickering model 410 ) an extra beam and
nose bolt was added, as well as a fixed stretcher to stabalise the plate
stress, and it's effect on the rim assembly. 
Del was at his best with the design of the scaling on this small grand,
pity they did'nt use all his specifications.

Now that's clear like mud.

Have a good day. Roger



At 12:00 PM 10/03/00 -0600, you wrote:
>>            No bearing on a GH1, --------------  //  --------------- 
>>The fault was traced to an inner to outer rim separation. 
>----------------  // ----------------
>>Roger
>
>
>Hi Roger,
>Ok, you got me. I don't get it. This is something I have to have explained.
>How could even taking the outer rim off entirely affect the bearing, much
>less a local separation doing so? Also, if the separation was deemed the
>boojum responsible for the lack of bearing, then re-attaching the inner and
>outer rim must have restored the bearing, right?
>
>Ron N
> 
Roger Jolly
Saskatoon, Canada.
306-665-0213
Fax 652-0505