Friday 26 February 2021

Walnut Decisions

 I haven't posted recently as I'd not done anything on the 2nd Walnut bow.
Mind I have been tinkering about with my lathe. I made a nylon leadscrew nut as the old cast iron one was very sloppy, it took some doing, but was an interesting job and seems to have been worthwhile as the lathe feels much better now. The picture shows the first try out version. It's a 5/8" 8 tpi ACME thread)



I've also done a couple of videos looking at what happens when you draw an even slat of bamboo from off centre like a Yumi bow, this was following some discussion on one of the archery forums. There seems to be several types of idiot... on sort will ask questions and then totally ignore the detailed answer, another sort will merely change the question without answering any of the points raised... regarding the Yumi, it was someone who quoted some 'O level' physics, as if I didn't know it already.

Anyhow I did a follow up video to show that what you see doesn't necessarily lead you to draw a sensible conclusion, especially if you don't correctly apply the physics (Hooke's Law in this case).


Anyhow back top the plot with the Walnut, I've shot a few more arrows through the first one and that's made me decide to tiller the 2nd to 50# @27" initially as a 50# flight bow. If it takes no set then I may add some extra recurve at the tips to work it harder. I'll go for 27" draw as I have some 27" flight arrows.
Hopefully in a month or so we'll be able to get out shooting again.
I had my first Covid vaccination a couple of days ago, I felt a bit achy and tired for 24 hours, but just took it easy.
Hope you are all staying safe and not going too stir crazy.

Friday 5 February 2021

2nd Walnut Bow


 I've started on one of the better Walnut staves, got it roughed out, steamed out some deflex, sideways bend an twist, which I did all in one go. I've tried it on the tiller just to see how it was moving. It's showing the right limb as weakest just out of the fade, but there is plenty of weight to play with.
 I've rather stalled now as other things have piqued my interest. Not really sure what I want it to turn into...
Meanwhile, I've been trying to turn a new leadscrew nut for my little lathe as the existing one is sloppy and has a load of backlash. I'm turning one out of nylon 


which will hopefully be tough enough for the loads imposed on it. Nylon is also self lubricating and being slightly flexible it allows a tighter fit.

Anyway, it kept me out of mischief and I practised on a chunk of Laburnum first. It's quite a fiddly process turning an internal ACME thread, but it taught me a good deal... (one thing being that metric and imperial aren't interchangeable!)

It took a bit of fiddling and fettling to get the nut to fit correctly, but it seems to work very well, the bcklash is gone and it actually seems to give a smoother cut, even taking off 20thou which is more than I'd normally take on this small lathe 10-15 is my usual max. Of course it could just be my fond imagining.