[nikidasi]

Dear, guys,

I have been planning to modify my SEIKO 7548 quartz diver. I am going to use aftermarket hands with "meatball" (the rounded part with lume inside) on the head instead of on the tail of the second hand like all SEIKO quartz diver.

As we know, all (?) SEIKO automatic diver has meatball on the head and SEIKO quartz diver on the tail (SKX007 is the exception). I guess on automatic it helps preserve rotational momentum like an engine's flywheel. While on quartz, it serves the otherwise, to cancel out the momentum and reduce impact on the quartz power train. Below pictures show what I mean with "meatball". Pictures taken from Yeoman's blog.

The question is: If I use second hand with HEAD meatball for the quartz movement, will it damage the gears or any component inside the quartz engine? Please chime in. Thanks in advance.

 

[nikidasi]

Just my opinion, but I think the position of the meatball is chosen purely for cosmetic reasons. I don't think you'll do any damage to your quartz movement.

Thank you, Sir Les and Valvestem,

Sorry for the long overdue reply because I was waiting for the answer from Yserv. I suspected that an automatic second hand on quartz engine will damage the gears inside. Yserv forward the lume ball position question to Mr. Tokunaga and below is the answer I just received today:

from: [email protected]
sender time: Sent at 12:43 (GMT+09:00). Current time there: 21:08.
to: [email protected]
date: 28 May 2010 12:43
subject: Inquiry about the repair of your SEIKO watch / our Ref. 22248

Dear Mr. Sadikin,

First of all, we are sorry for my misinformation concerning the lumi's position of the hands. We contacted with Mr. Tokunaga and knew the following matter.

Since the power of the torque for the quartz watches is weak, in order to escape the stress, the lumi put on the tip and the tail of the second hand, which is maintained the balance of the second hand.
Therefore, the second hand for the mechanical divers' cannot use for the quartz divers' watch.

Since we can repair of your divers' watch (case No. 7548-700B) by using the substitute hands, we ask you to contact with our national service center, which was mentioned in our previous email. They will transfer your watch to us for the repair.

If you have any further questions, please feel free to contact us.

With best regards,
Hiroko Nakajima, CS Dept.
May/28/2010

As for the ORCA which has lume ball on both ends of the second hand, I believe they cancel out each other and keep the center of gravity around the axis.

I canceled the 7548 modification project due to very limited hands set alternatives that is suitable for quartz engine. I went on with restoration project instead. Here is the result.

BEFORE:


AFTER:
[img]
[img]

 

[nikidasi]

Although Yserv may be technically correct that you can't use a hand from a Seiko auto diver on your quartz due to balance/torque issues, there are many, many quartz divers that use hands with a "meatball" out towards the end of the hand (a quick search of the web just showed me examples from Luminox, Freestyle, Citizen, Omega and others). The key seems to be that the hand must be counterbalanced. So you could find an aftermarket meatball hand counterbalanced for a quartz movement and use that. As Les and Gabe pointed out, it's mostly a design decision.

paul

Hi Paul,

Yes I am aware that lume ball position is purely design decision. My CITIZEN Eco-drive diver has lume ball at the tip of the second hand but it also has thick tail as counterbalance and keep the center of gravity on the axis. My previous question is about technical design decision instead of styling design decision.

Taking picture of the 7548 quartz diver under long exposure (a couple of second) will reveal that the (well-balanced) second hand is rocking a little bit every time it hits the stop. Imagine replacing the second hand with the one from 6309 automatic diver with unbalanced lume ball weight at the tip amplifying the rocking. That is what I am trying to say.