Apologies if you also follow the bagpipe makers group on Facebook and are seeing this request twice, but I suspect there are probably a few folk here that don’t and might have something interesting to say.
Anyway, I am starting a little project to build some concert D drones in Delrin/brass and having knocked up the start of a design I have a few questions/uncertainties. I’ve started a blog to keep track of it all - http://slowdrones.blogspot.co.uk/
First up is the mainstock design, which I have a rough idea what I want to do but I have a few questions that I hope you could fill in for me - included in the blog post, but things like o-rings on the drone switch, drilling/boring large holes in Delrin, and whether or not a mainstock cup is a good idea.
One thing I’d suggest is to use ABS plastic over Delrin if you can.
I find it machines better and accepts glue better too. Most glues just run off Delrin.
I wouldn’t bother with O-rings at all. You be making one huge big bushing anyway.
Is it OK to have the 17mm bass drone that close to the edge? It’s approximately 2.5mm from the outside edge.
Are you going to fit a metal collar on the stock. You’ll be fine if you do.
I think this can be tied directly into the bag with the addition of a tie-in groove near the bottom. Is there a substantial advantage to a cup?
If you don’t use a cup the end of the drone switch might be scraping the inside of the bag. No?
Not sure if the Delrin would be strong enough at that overall diameter and wall thickness.
What about a PVC tube/pipe.
Given the drones are also being made of Delrin, is it reasonable to reduce their diameter (especially the bass) from the plan sizes?
I wouldn’t reduce the diameters of the ends that go into the stock. They carry a bit of weight and need strength, especially the bass.
Are there acoustical considerations with a smaller stock size?
Wouldn’t worry about it.
For boring the hollow, I assume Forstner bits will be easiest, with a boring bar for the 1mm step. Assuming I can’t do it in one go, how many passes at what sizes should I be doing?
Again, PVC tube from the plumbing section in the local hardware. Or if you really want to splash out, a 2" diameter brass tube!
Yes, I thought that would work. My only worry there was the accuracy of hole size required. I think I will try it, and leave room to expand it for O-rings if I cack it up!
Are you going to fit a metal collar on the stock. You’ll be fine if you do.
I hadn’t planned to, but I like your idea of brass tube rather than trying to bore large deep holes. An 8" long 2" tube in 16g is about £30, but that’s not that much more than the saving in plastic! It will mean taking a bit off the 50mm rod but that seems fine with a millimetre of brass strapped round it.
Cup it is.
I wouldn’t reduce the diameters of the ends that go into the stock.
I meant more the mounts and general thickness of the drone but looking again at the plans I don’t think there’s much in it. Will forget about that for now.
I just wanted to draw your attention to the quite different design for delrin main stock that John Walsh uses for his delrin Scottish Smallpipes.
The “stock” is very short, the “cup” is very long (in effect) so that you can take the stock out of the cup and have access to all the reeds without having to remove the drones from the stock:
Of course this wouldn’t work when you need a shutoff valve.
The ‘plug’ design above is precisely what was used for early union pipes.
A stock cup is essential in order to rotate the stock, for best access to regs . This is sensitive to many factors including posture and chair height.
Anyone interested in main stock design should familiarise themselves with previous designs such as are shown in the NPU Coyne and Rowsome plans, and the Sean Reid Society publications (all available inline, the former to NPU members FOC and the latter free to all).
While we’re on the general subject and I have a pipemaker audience, one thing I noticed on most plans is that there isn’t detailed information on how the bass regulator receives airflow from the stock. I see there is a hole under the mounting plate on the side of the stock (e.g. page 12 of the Hannan Coyne plans)–where does that receive it’s air supply from? I don’t see the conventional dashed lines for hidden edges/features. 'm just curious, since I don’t have my own set with regulators to look at.
Have you had a look at Bill’s article? I think that answers your question - basically, it is fed by a tube from the disc against which the drone switch valve operates.
I hadn’t seen his article. Not sure if you are referring to the hollow stock guide, but I just searched for it/read it. Thanks for letting me know. I guess it could be done similarly with a solid stock although I’m not really sure how it’s typically done.
I’m not a solid stock maker but as I recall the old way was to drill through the side wall of the stock into the port for the middle regulator so as to take the air feed to the Bass.
A metal tube with a right angled bend or a mitred elbow is my method of feeding the Bass regulator on a hollow stock. If anyone needs photos of this send me an email!
