MIMF

My latest project is a large-body bass similar to the Ernie Ball Earthwood. After going through a few bridge designs, my latest is a traditional type with strings mounting through the soundboard and held in place by pins. Given the large size of the strings, I am using end pins instead of bridge pins. They have a 5-degree taper.
In my transitory fits of genius, I failed to account for the size of the ball ends on the bass strings. They will not fit through the bridge holes; but bottom out about 1/4" into the bridge.
As I see it, I have the following options:
1) Back to the drawing board
2) Load the strings through the soundhole (will be a problem when it comes to changing them as they will all have to be detuned)
3) Widen the holes in the bridge/soundhole/bridge plate only as much as needed to allow the ball ends to pass - this is the no-brainer answer but I know a lot of people feel that a snug fit is key to sound transference. This is my first acoustic project so I have no frame of reference, but I'd appreciate opinions on this.
4) Swap the bass ball ends for guitar ball ends - not an acceptable solution as this may turn into a production model

Thanks in advance.

I can see two relatively easy solutions:

1) The ball end has a rectangular profile entering the pin hole. File a rectangular profile in the hole, starting where it begins to hang up ~1/4" inside the hole. Carry this down through the bridge plate, making it just large enough to pass the ball end. There will still be quite a bit of bearing surface for the pin, as you are just doing the corners, gradually getting wider as you go deeper in the hole.

2) Probably more mechanically stable - just nick off the corners of the rectangular profile of the ball end until it fits through the hole. This part of the ball end does not bear on the bridge plate, so can easily be dispensed with. Of course if you are doing production this isn't the way to go unless you want to include instructions for changing the strings.

I think I would load through the soundhole. I understand that you are using UBass strings right? If so the ball is quite a bit larger than on a BG string. My rationale would be to preserve the hole size for the buyer (In the event they wanted B Guitar srings in the future.

Well, I tried loading through the sound hole - no dice. The bridge is too far back and my arms aren't skinny enough (and I'm a fairly skinny dude). This is just a prototype, so increasing the sound hole size is actually on the plans for the next one, but I think I'm going to try Peter's #1 solution. I'll keep you apprised,

For loading through the sound hole, put a thread or string through the pin hole and you can fish it out through the soundhole. Then you can use the thread to pull the string through the pin hole from the inside.

Rodger Knox wrote:For loading through the sound hole, put a thread or string through the pin hole and you can fish it out through the soundhole. Then you can use the thread to pull the string through the pin hole from the inside.

Thinking the same thing Roger.
Please keep this alive Paul it is interesting (at least to the bass players).

Is there a solid reason for using the strings you're using that have such large, ummm, balls?

While there are countless "workarounds" for getting the instrument strung-up and usable for you at this point, there's no way you can have a successful 'commercial' version of such that requires its owners to go through these antics; you'll need a complete re-design of the bridge system, I fear, or a change of string type/brand.

You could always turn your own larger pins (if there's room on the bridge for bigger holes).

As I recall the Earthwood basses used something other than end pins as bridge pins. They looked like end pins but were longer and wider. Get the proper pins and make the holes large enough to use the strings.

The string/thread idea is a sound workaround for prototype testing but not for production. I am considering getting lathe-savvy and turning my own pins, but for now I've got a few ideas and suggestions, including filing four corners in each string hole while still maintaining an overall round profile so that the ball end (basically a square in profile) can pass in but the pin can still have decent contact.
As far as I can determine no one makes a set of strings with small ball ends.
Michael, if you can find a supplier for those pins, you have better contacts than I do. Some of the Earthwoods used pins, others were loaded through the tailpiece from the back.

Lots of folks think bridge pins on an acoustic bass is a bit of a pain, they don't really work as well as on guitars, anyways. The strings and pins are just too bulky, I guess. Pinless bridge? I guess that is option #1...

The real solution is to make the pins yourself. You could even do different sizes if that works better. There's any number of ways to do it without a lathe, a hand drill can be made to work. I used to make my own pins, but I've relaxed my idea of "handmade" and buy the premade pins.

If you are planning a production line, you need to design the bridge such that stringing is more foolproof. For testing, I was going to suggest something similar to Roger’s idea, but using a long curved (stiff) wire with a small loop on the end. You can put it in the pin hole and it will come up through the sound hole, then hook the string end on and pull. . .

Well, I ordered a variety of string sets. It turns out that the actual Earthwood strings are made with a smaller ball end that will work without additional effort. So problem solved, unless the buyer wants to use different strings...