Author Topic: Strike line on a Mark II  (Read 1255 times)

Offline 4kinga

  • Sparkletop
  • ***
  • Posts: 86
    • View Profile
Strike line on a Mark II
« on: March 18, 2018, 01:36:52 PM »
I have a Mark II.  The action always felt nice and tight, but the sound was always dull with little dynamics.  I replaced the hammer tips to no avail.  Adjusting pickups helped a little.

This weekend, I adjusted the strike line. Wow!  It came alive with great dynamics, tone and bark.  I had to shim the treble end about 3/16".  Now that its adjusted, I need to mount the harp.  However, on the Mark II, these are aluminum rails with tapped holes that machine screws go into.  Also, the location of these new holes are close to the original holes on the bass end of the harp.

My questions are:
- Should I make new holes in the harp to get the mounting holes far enough away from the original holes in the aluminum.
- Does anyone have any hints on tapping the aluminum?

Offline sean

  • Mark III EK-10
  • *****
  • Posts: 959
    • View Profile
Re: Strike line on a Mark II
« Reply #1 on: March 18, 2018, 07:40:32 PM »

I think you should go ahead and drill a new hole in the harp frame and tap a new hole in the extruded aluminum harp support.

I think you only need one hole on either end of the harp.  Unless you plan on dropping the piano down the stairs, one bolt should hold it.  Okay, maybe two bolts would be safer for the teamsters to load it into the truck.

The bolts are #12-24, so buy a #12-24 tap.
Six bucks at the orange apron place:  https://www.homedepot.com/p/DEWALT-16-Drill-and-12-24-NC-Tap-Set-DWA1408/204787239
No wait, even cheaper: https://www.homedepot.com/p/Gyros-10-24-Thread-Spacing-High-Speed-Steel-Plug-Tap-91-11024/204625853

Aluminum is very easy to tap, so you should have no problem.  The section of the harp support is quite thick, so you will get clean threads and a good grip on the bolt.

The only reason that you do not want to simply drill a hole in the harp support and try to put a nut underneath is that there is not enough room for the nut against the side wall of the aluminum extrusion.  You might be able to run a hole in a place with enough clearance, but it will be a bit risky.  Tapping the threads is easy enough.

Run a pilot hole (7/64", 1/8", 9/64" whichever bit is sharpest) through the harp frame, and then transfer the hole location to the harp support.  I would not drill the harp frame while it is installed on the piano.  I would drill a quarter-inch hole in the harp frame, and a 11/64" hole in the harp support.  If you mount the tap tightly in the chuck of a battery-powered variable-speed drill, you can tap the hole with a gentle touch on the trigger.  Go slowly.  The drill will give you very good control of the tap (better than you would get with a traditional tap handle).  For this small number of holes, you can get away without lubricating the tap, or just using spit.  When you get through to the other side, flip the drill into reverse, and back out the tap.

Sean


Offline 4kinga

  • Sparkletop
  • ***
  • Posts: 86
    • View Profile
Re: Strike line on a Mark II
« Reply #2 on: March 19, 2018, 11:09:20 AM »
Thanks for the info, Sean. 
If I'm drilling, I might as well drill four holes and lock it in.  (Although, I don't plan on moving it any time soon.)  Hopefully, I'll get to this next weekend.

Offline Ben Bove

  • Vendor
  • MIDI Mark V
  • *****
  • Posts: 3280
  • Formerly bjammerz
    • View Profile
    • Retro Rentals Website
Re: Strike line on a Mark II
« Reply #3 on: March 19, 2018, 01:58:48 PM »
A lot of Mark IIs came out with not-that-great strikelines, as the aluminum frame pianos were designed to be assembled as-is.  I was told the harp wasn't hand-located by technicians for the optimal spot like on wooden frame models.

I do find it odd that you had to shim the harp even higher on the treble end.  Before you lock it in, you may want to take another look at the treble placement.  Often when a shim is put in and the piano sounds better, it's because the hammers are now hitting the tines farther back, and actually hitting the optimal spot only because the harp went higher.
Retro Rentals
Vintage Music Gear

http://www.RetroRentals.net
(818) 806-9606
info@retrorentals.net

FB: https://www.facebook.com/retrorentals.net/
IG: @RetroRentalsNet

Offline 4kinga

  • Sparkletop
  • ***
  • Posts: 86
    • View Profile
Re: Strike line on a Mark II
« Reply #4 on: March 21, 2018, 09:09:14 AM »
Interesting point.  I'll take a look at that tonight. 

The prior treble distance was very shallow: a little less than 1/4".  (I had to adjust all treble dampers after.)  I'll try removing the shim and see and listen to the difference. (The shims are just washers right now.)

For reference, I had to move the harp about 5/16" back on the bass and 3/8" on the treble.  No shim on the bass (measured 3/8" hammer distance) and a 3/16" shim on the treble.

Offline Ben Bove

  • Vendor
  • MIDI Mark V
  • *****
  • Posts: 3280
  • Formerly bjammerz
    • View Profile
    • Retro Rentals Website
Re: Strike line on a Mark II
« Reply #5 on: March 22, 2018, 04:15:54 PM »
The hammer tips you used - are they the different heights version where they're shorter in the bass than the wood core treble tips, or are they the earlier style at all equal heights?  That would explain eliminating the bass shim and maybe raising the treble shim.  The factory tips on a Mark 2 were graduated in height, and that's how they set the escapement vs. through shims.  All aluminum frame pianos had the exact same height shims from the factory.
Retro Rentals
Vintage Music Gear

http://www.RetroRentals.net
(818) 806-9606
info@retrorentals.net

FB: https://www.facebook.com/retrorentals.net/
IG: @RetroRentalsNet

Offline 4kinga

  • Sparkletop
  • ***
  • Posts: 86
    • View Profile
Re: Strike line on a Mark II
« Reply #6 on: March 23, 2018, 09:07:41 AM »
They are graduated, with wood core on the treble end.