Mk2 Plastic Balance Rail Replacement... thoughts?

[MechYeti]

Hi all,

I have a Mk2 that I have been restoring, and in the process I have been reading a lot of hatred towards the Mk2's plastic balance rail.  I understand the sentiment, it is pretty easy to flex and could see that being problematic with aggressive playing.  I am a novice player and would probably never have an issue, but I just really like tinkering.  I started drawing the balance rail in CAD to design something that I thought would be easily to CNC or lathe out of aluminum (6061 or 7075).  My thought is to possibly replace the balance rail and the front rail, but I am primarily focused on the balance rail for the time being.  I am working on a piece that would directly replace each plastic part on the rail, and I only have the octave version designed thus far, not a 13 or 7 key version.

I know there are a few Mk2 regulars on here that have plastic key versions, I am just curious how many people would actually be interested in upgrading something like this.  I am also wanting someone to tell me that this is a ridiculously dumb idea and that it won't actually help anything so stop trying.  I'm not a mechanical engineer, so my CAD skills are still developing as I only get to do modeling on these sorts of home projects.  Cost is of course a concern, and obviously I would need to shop around some before manufacture, but it looks like I should be able to get about 5 pianos worth for $250/piano (again, balance rail only at this point, and only the 73-key version).  Much of the cost ends up as setup time (which is fixed), so machining multiples greatly reduces the per piece cost.  Of course I am hoping I can find someone locally that can bring that down quite a bit.

I have attached  the rail base and a single peg.  I have not done the assembly yet to show the final version with all of the pegs populated.  Any thoughts?

[sean]

I am proud to be the first one to tell you that this is a ridiculously dumb idea!  However, don't let that stop you.

First of all, I am upset about the premise that the plastic balance rail is "a problem" or even "the problem" with the plastic-keyed Rhodes pianos circa 1982-1983.  I have seen a few rare complaints about the plastic pins breaking when abused, but I have never seen what I would think was "hatred" specifically aimed at the balance rail.

For the record, the balance rail in my plastic-key Rhodes is just fine.

Changing the balance rail to aluminum may solve the rare issue of broken balance rail pins, but at what cost?  I wouldn't pay more than the cost of a plastic balance rail section to replace a broken pin.  Twelve bucks:  https://www.vintagevibe.com/products/rhodes-mark-ii-plastic-key-pins  OUCH!  The front rail sections are expensive!!

How will you polish the aluminum balance rail pins so they are as friction-free as the ABS originals?  That would be a costly pain.


If you want to advance the state-of-the-art in plastic-key Rhodes action, please figure out an elegant solution to the insane key bounce!  The plastic-key Rhodes action is impressively loud and bouncy.  I have always wanted to rout a trough in the piano case bottom under the back end of the keysticks (under the felt strip), and fill it with damping gel (like the stuff VV sells for Clavinet string damping), then put a layer of felt over that.  I realize that a lot of testing would be required to arrive at the best way to stop the keys from bouncing, and it would take more effort and money than my plastic-key Rhodes is worth.

However, I have not a leg to stand on when it comes to criticizing passionate projects of moderate lunacy - I am fool enough to follow my own goofball ideas.

If this is a project that captures your imagination and grabs your heart, then by all means proceed!  But don't be embarrassed to quit when you get halfway down the road and have run out of steam.  Turn off into the woods and start a new project.  At least you will have learned valuable skills in drawing, 3D modelling, and machine tooling.

Sean

[MechYeti]

Sean,

This is exactly the sort of response I am looking for! Thanks for being the first to call me out!

The balance rail pins would be polished, I can specify finish when machining.  Polished definitely adds some cost. But at the end of the day, sometimes you need people to keep you in check and say just because you CAN doesn't mean you SHOULD!  As I said, I am not a player that would really benefit from such an upgrade.  Sometimes you "solve" problems that really aren't problems, but better to find that out now than spend a bunch of money turning your solution into reality.

The bounce problem is an interesting one...  My piano has a groove under the felt, and my key dip was a bit on the large end so I ended up replacing it last night.  I only had a single felt strip and it looks like mine was a double stacked strip, so I bought some stiffened felt to build it up to the proper height and glued it in.  If I hadn't just glued that, I think your gel + foam combo would have been a great thing to test.  I wonder if something could be layered in front of the foam so that it would help act as a preliminary dampener further up the lever arm before it hits the felt.  The problem with that is obviously doing so without affecting key dip and/or actuation force... I'll think on that a bit more!

As always, thanks for the great feedback.

[Tom999]

As a fellow tinkerer, I can get behind this little endeavor. Totally not practical and probably not worth it but hey why not lol.  I just recently restored an '82 suitcase with plastic keys and while cleaning all the balance rail pieces I had the exact same thought...what if the posts were aluminum and screwed into the base so they could be replaced at some point.

I did wonder if the plastic on plastic motion is causing a bit of the clickity clack and if so...could the posts be a little thinner like the wood models and could we add some type of insert into the key to mate it to the post.  That way you'd have the material stability and precision of the plastic key but with the softer dampening and structure of the wood key.  However there's the front posts also that are plastic on plastic so they would probably need to be replaced also to totally minimize the clack.

For your design, it's not clear if you mean to have the base machined out of aluminum or somehow make it plastic again. If you're going to have that machined then I'd look into simplifying the base overall.  Seems like it would only need 2 holes to mount to the wood shell, and could probably lose the front/back bevel and the four corner fillets. Now I'm wondering if the base could be 3d printed with female brass inserts installed for the posts...or maybe capture nuts. Tricky part is the precision placement but a well-calibrated printer and maybe an alignment jig could help with installing the inserts.

Then you just have to worry about the posts. If there isn't something off the shelf, which seems like there would exist something already with like 5 to 10 mm of thread and smooth for the rest of the post. Or maybe a thinner, fully threaded post where you then fit some kind of sleeve over it so the key mates snugly.

Along similar lines of tinkering for tinkering's sake...I ended up modeling the dowel holder in the back and printing that in PETG. Also replaced the front rail felt with TPU pieces that match up with each front rail since the felt seemed like a nasty/dirty solution.  The keys aren't really supposed to come in contact with the felt in any case. Attached images of what I'm talking about.

For the key bounce - I built a new wood shell for the top and did not groove out a strip for the back felt. I just put the correct replacement felt right on the layer and that seems to have helped a bit with the action.  After all my tweaking I feel like I'm in a good place.  The plastic keys get a bit of a bad rap but as someone in a high-humidity location they actually are a good choice for me.

[sean]

I think the worst part of the clacking sound is the hammer itself bouncing.  Plus, the key does thump a few times on the back felt.

I get no impression that any of the clacking sound is from the contact surfaces of the keypins.

Sean

[MechYeti]

Hi Tom,

I was thinking base out of aluminum.  The post itself is a lever arm that I would think would flex a plastic base quite badly.  I think you could definitely overlay plastic over the aluminum.  But I really think that would only work on the balance rail.  The front rail itself would have to stay plastic or go all aluminum posts, as the smaller diameter is going to give you diminishing returns.

Your parts look awesome, do you print them yourself?

Quincy