Friday, 29 July 2011


I didn't add quite as much back set as I'd wanted and that's meant theres a small gap in the tip of the splice on the back of the bow (top of the splice on the last pic). I'll fill this with epoxy and Osage dust just to stop moisture getting in, it won't add any real extra strength.
I'm not entirely happy, but we'll see if it holds once it's a bow.

Thursday, 28 July 2011

Splicing Osage

Blimey, getting the splices to mate up nicely was hard work, it took a lot of fiddling and fettling as there seemed to be big gaps when I held it up to the light. I ended up opening up the V cuts to become flat bottomed and sawing the tips off the points which fit in the Vs.
It was easier to get a fine rasp in there. I tried all the tricks like assembling the joint with a piece of sandpaper in there and the pulling it out to remove any high spots. Eventually with plenty of patience and a several goes at it I got the slice to fit together reasonably well. A pice of flat steel from an old saw blade with sandpaper wrapped around it was useful for getting down to the bottom of the Vs.

I decided to try Resintite adhesive as it's realtively cheap and easilly available and has some gap filling properties, it was going to be that or Araldite precision.
The Resintite is a very fine powder which you mix with water, my wife didn't like me using the kitchen scales as the stuff is a bit toxic I think, so she banished me and the scales to the garage...just as well as I did spill a bit.
I bound the joint with wide rubber strapping (cut from a car innertube, or EPDM roofing sheet)
To apply pressure longitudinally I jammed the bow between a wall and the leg of my shelving, with some scraps of wood as spacers, leaving the middle slightly raised. By pressing down firmly on the middle it forced the joint together. I left it with the middle raised by about 2" which is the back set (a bit like reflex).
I'll take the rubber strapping off tomorrow and post a pic of the joint, you'll be able to see how it has been opened up compared with the pic in the previous post.

Monday, 25 July 2011

Splicing the Osage

I cut a splice on a scrap of 2x1 pine just to test the theory. The Osage however isn't straight! I layed it out slightly S shaped with a straight line (taut string) passing from tip to tip through the centre of the handle area. This meant the area for the splice didn't line up quite right.
I'd originally marked it up with the two ends of the billets butted up together, but once spliced they actually overlap, so having sawed one splice I readjusted my marking out on the other billet to get it all in line.
It was a bit nerve wracking sawing it, and you can see the splice needs some work with a fine rasp or file to make it fit snugly before glueing.
I'm not sure what glue to use, I don't have any of the generally accepted glues, but I suspect a good quality epoxy will do (after all it's holding my Asiatic Recurve together!)
If necessary I can take out some of the bend and twist on the tips later if necessary.
That's about it for today, although I may tidy it up to see if I can get a snug fit.
As it's the first time I've used Osage, I shall pretty much follow the 'recipe' in the Traditional Bowyers Bible vol 1.
I shall put my own twist on it by putting a bit of back set on the limbs when I glue it up.

Sunday, 24 July 2011

Osage Orange

Osage grows in much of the USA and I was luck to be offered a pair of billets by one of the guys on the Primitive Archer website (from Texas). I sent hime a short Yew stave in exchange (Taxus to Texas!), but I got the best of the deal as the Yew is much lighter and the postage was less, I'll try and send him a stave suitable for a longbow later in the year.
The Osage feels very different to the Yew, much harder but not elbow jarringly so, and it cuts quite crisply, on the end grain shot I'll work it down so the first thick dark ring becomes the back of the bow (the pale wood to the left of that ring is sapwood). The other pic shows some Yew for comparison, The Osage is almost day-glo yellow, but it ages to a deep brown.
I'll be splicing the two billets of Osage, I've not done that before, so I'll try it on some scrap, I'll post pics of course.

Saturday, 23 July 2011

What an Idiot!

I couldn't understand why my force draw machine gave a lovely big vertical deflection when calibrating it on the dial spring balance, but when I tested it with a bow the deflection wasn't the same!!?? In fact it was about half what it should be!
Had the bows mysteriously lost weight?
I investigated carefully by attaching the balance to a bow so I was pulling both at once, then the penny dropped.
I wasn't a factor of 2 out, it was more like 2.2
Have you twigged yet? Yes I was reading Killograms instead of pounds when testing with the dial balance.
I shall add another pulley to get more vertical deflection.
What an idiot!

Friday, 22 July 2011

Force Draw Plotter Working

The video is a bit brief and shows a spurious line plotted as I let the bow down, this is because the return spring on the vertical pen travel and the horizontal slide are both a bit slow.
This next video shows the movements separately.

Wednesday, 13 July 2011

Base Plate and Vertical Travel

You probably can't quite see how it works yet, I have enough trouble visualising it myself!
The horizontal section is now mounted to the base plate, free to slide up and down on two steel tubes. The only thing holding it down (other than gravity) is the spring from the spring balance.
As the bow is drawn the spring will stretch and the horizontal section will lift slightly, this lift will be linked to the pen to draw the vertical displacement onto the graph.
If you don't follow that, just trust me I'm an engineer! If you look closely at the first pic you'll see the spring has come off it's lower mounting (whoops).

Monday, 11 July 2011

Horizontal Travel Mechanism

The mechanism is built with wood, screws and bent wire coathanger, this is so that it can be taken to bits and re-made in a better and more reliable fashion, this is just the mk1, or to use modern engineering parlance a 'proof of concept model'. I prefer the good old fashioned term 'prototype' myself but one has to keep up to date (cough, splutter). Got a bit more done this evening,

It works ok, but the string needs to attached carefully at one side of the roller to get it to track correctly and the plate which will hold the graph paper will need a top guide as it gets kicked off at the slightest provocation.
The wire hook will hook over the bow between your hands as you pull the bow upwards, 28" of travel makes the graph plate slide along about 10".

I've mounted the spring and fitted two lengths of 16mm diameter steel tube to a plate of 1"ply to become the base. Hopefully I'll have some sort of basic working arrangement soon.

Friday, 8 July 2011

Hickman's Bow Weighing Machine

Clarence N Hickman the Father of Scientific Archery, is the title of a book I've had for many years. He was a prolific inventor of all sorts of things* and designed the first modern recurves.
He built a machine which would draw the graph of draw weight vs draw length automatically.
You stood on a plate to hold the machine down, hooked the bow string onto it and pulled the bow upwards. As you pulled up, a plate with a sheet of paper was pulled across, and as the draw weight increased a pen linked to a spring balance moved up drawing the graph.
I'm trying to build myself such a machine just for the fun of it, rather than the serious research he did it for.
Essentially there are two parts, the horizontal travel where the 28" draw becomes about 12" of movement of a sheet of paper, and the vertical travel where the movement of the spring scale is translated into about 8" of pen travel.
The spring balance is a vital part of the machine, and because I recently bought a new dial balance for measuring draw weight, my old spring balance is now available to be recycled into the machine.
I'll post some pics once the first bit (horizontal travel section) is complete. It will be a bit rough and ready as I'm designing it as I go along and it's mostly wooden construction.

* High speed photography, rocketry, acoustics. He was also an amateur magican.
The book is ISBN 0-9613582-003 for anyone interested.

Wednesday, 6 July 2011

More Scavenging

I went back and tidied up the last badly sawn Hornbeam and took a scrawny length of the bit which had been cut down. One whole side of it had been chaffed away, with no bark and was rotting. You wouldn't think it was worth picking up, but a few minutes with the axe chopping away the bad stuff has given me a stave to make a quick primitive bow with a D shaped back.
It will allow me to have a try with the Hornbeam as it will season quickly. I painted the ends of all the timber with PVA builders adhesive to stop it drying too quick at the ends and splitting (checking), I've read that Hornbeam is prone to checking. I also picked up a nice fat bit of Hazel, a bit of rot has started at one end, but there should be a stave in there.
The beauty of picking up stuff like this is that you can try it out without the worry of working some carefully glued up stave or a precious bit of Yew which you've been seasoning for a year, it's also good to dry different woods.

Monday, 4 July 2011

Tidying the Woodland

I walked up to the town centre via the woodland, there were at least 3 Hornbeam trees which had been sawn down badly at about 2-3 feet from the ground, with a cut which had split down the stump.
I returned later with my saw and tidied up two of them cutting them at about 45 degrees about 10" from the ground, hopefully they'll sprout up next spring.
A guy was passing walking his dogs and said he'd seen a party of school kids from the secondary school the other side of the wood doing clearing and tidying of the pathways and he though a couple of the kids had strayed from the supervision and got a bit saw happy. I'm in no position to criticise, have done done my share of daft things as a kid.
Anyhow I managed to salvage a nice length of hornbeam from the one in the pic' which will hopefully give me a nice pair of billets to splice together into a decent length stave. It's 51/2" diameter and 56" long (whoops I originally put 5'6").
I've not spliced billets before, when I get round to it I'll post the pics.
It weighed a ton and I was sweating like a pig by the time I got home with it across my shoulders like a yoke. Second pic shows how I left it. I also cut a skinny stave from one of the branches, it might make a little primitive bend through the handle bow. I'd rather pick up a stave and then find it's no good later rather than sit at home wishing I'd picked it up.

Friday, 1 July 2011

Odds & Ends

I've been busy doing the fascia and guttering on the front of the house, so the garage now looks like a building site with no room to work on bows.
I've still been busy thinking about bows and a guy in the USA kindly offered to ship me some Osage as I've never used it. It turns out that the cost of shipping is rather high, but oddly, it seems cheaper to ship it the other way!
I had a bit of Yew left too short for a longbow which I though I would ship to him as a sort of trade, I was a bit disappointed as a small knot in one end actually ran along under the sapwood for almost 3" reducing the stave from a respectable 63" to a miserly 58". The guy is a hugely experienced bowyer so I'm sure he'll make use of it.

A while back I posted a picture of some Yew I was hoping to cut next year, I got in touch with the forestry commission as it is on their land. The forester responsible for that area said it would be acceptable to cut it as it's just a side branch, we have to agree on a price first.
Yews are part of a rare and endangered habitat so obviously they don't want people felling trees or taking wood in an irresponsible manner.
I shall offer a good price to compensate for the similar piece I cut without permission many years ago!