Bow Scale Peak Hold

I've been roped into decorating the lobby, blimey it was only done about 15 years ago ;-) ...

So, I was looking for a quick little project that I could do whilst waiting for walls to dry etc.
A peak hold needle for my bow scale is something I've been thinking about for ages and it gave me an excuse to play about on my lathe.
It's turned from brass in two parts with an M4 thread, the actual needle is cut out of some tin plate (an old olive oil can ... I knew it would be useful!) and glued onto the brass with epoxy. The vital friction is supplied by a cardboard washer, the two parts are nipped up to give the right degree of friction and a spot of superglue is applied to the thread.
The threaded hole goes right through (unlike in the sketch) and the needle has a hole in it so I can see the thread to apply a spot of glue.
The sketch was just a rough guide and some dimensions needed changing once it was tried on the scale... notably the thickness of the brass section which sits inside... when I first measured (having drilled the hole in the clear plastic) I forgot to subtract the thickness of the plastic, so its, 7mm not 10mm

The needle is coloured black with a felt pen... it has a little tab bent down towards the scales o that the red needle pushes it round as it advances.

It works a treat, I'd like to knurl the knob but I've no way of conveniently holding it tight enough in the lathe chuck without risking damaging the M4 thread... if it ain't bust, don't fix it.
It will be handy for doing force draw curves and measuring the draw weight of the crossbow which is very tricky as it's difficult to draw it and see the scale.
Notem the scale has the Kg markings painted over and bold lines added every 10 pounds, with big spots every 50 pounds, this helps it show up in video footage.

Update:- I had to modify the red needle a bit as the forked back end was also moving mypeak hold needle! I just trimmed a couple of mm off the forked end.
I then set up to measure the crossbow draw weight. I was a tad surprised to find it was only 73#, but I s'pose the performance is pretty good considering. I may increase the draw length a little more taking it up to about 80# which should give the speed a nice boost, but I don't want to over do it as it is perfoming nicely now and the weight is very manageable.

Sighting the Crossbow

I did some more tinkering trying get the scope mounting more solid. I milled a piece 140mm length of 4mm aluminium alloy plate to a taper and put that between the scope rail and the wooden latch cover of the crossbow. That is much more solid than just shimming one end of the rail.
I checked the sighting at 10 yards and confirmed it was pretty good vertically (aiming 3 dots low).

While my better half was out ;-) I set up in the garden, the target boss placed in the doorway of the garage and I put my workmate and a chair near the summer house giving a 20 yard range.

Resting the fore-end on a tightly rolled old duvet and just holding the pistol grip of the crossbow in my right hand and the left cupping the butt of the pistol grip, gave a really steady picture through the scope. I was hoping for a cross hairs on target at 20 yards so that's how I was aiming.

1st shot right height but a couple of inches left. I adjusted the cross hairs on the scope having removed the protective cover. It had an arrow with "L" but does that move the crosshairs left or where the bolt impacts? Anyhow, try it and see.. I turned it 1/4 of a turn left (anticlockwise).
2nd shot, plus 2 others, to see how it grouped... 2" right and all bolts within a finger width of each other... click the adjustment back a bit.
The subsequent shots slowly walked left towards the 10mm black dot I was aiming at as I slowly adjusted the sight.
I cocked the bow for a final shot and though I'd see how it shot off hand (standing with no support).
The image was waving about all over the place compared to how it was when supported, but I relaxed a bit and brought the cross hairs smoothly onto the spot... now theoretically you should squeeze a trigger, well that's fine when you are supported and steady... conversely you don't want to snatch at it... BUT if the trigger is built and set up correctly it should pull in line with the shot and not kick the shot out of line.
(I'm no authority on this sort of thing and have little experience*... it's all just my opinion, so feel fee to disagree, comment etc).
So as I came onto target and popped off the shot... trying to stay relaxed, both eyes open.. it looked good as I saw it hit home through the scope, but it was hard to see exactly amongst the other bolts and holes in the target. A careful look though the scope revealed it had clipped the spot!
I was certainly happy with that, I'll have to try it at 30 and 40 yards sometime and maybe go round a field course, although it is to a great extent just an academic exercise.
Of course it was just one shot...

* I have spent a good deal of time however discussing these things with my brother who is a good shot with shot gun, air rifle and has even shot 303 at Bisley.

Crossbow Tinkering

I've grafted 20mm of extra length onto the end of the track, pretty much what I'd sawn off when working with the wooden prods. This gives extra draw weight and draw length which will give a faster flatter trajectory. Whilst doing this it became apparent why I was shooting all over the place, just about every screw and bolt was loose, presumably shaken loose by the recoil.
I got it all back together nice and secure, I also reserved the centre serving which had worn through, well the to be more accurate, the second layer had worn through, but the first layer was still sound.

Taking my brothers advice, I got myself set up in a seated position with the crossbow supported on a tightly rolled old duvet resting on my workmate at 10 yards range, working on the premise that I wanted to be aiming 3 dots low at 10 yards to give me the cross hairs on target at about 20 or so yards.
1st shot, steady as a rock 3" low 4" left. I wanted to adjust to the right and it became obvious that I had too many sources of error/adjustment. The scope rail is screwed into the wood block that covers the trigger mechanism/latch with 2 wood screws (plenty of play there) and that block is screwed into the stock with 2 off 6mm bolts which also have slop/adjustment. I slackened the bolts and tweaked it.
2nd shot, same height (good) 4" right. Adjust again...
3rd shot, same height (good) 1/2" left, that'll do for now.
Looking at the height, I obviously don't need to be aiming 3 dots low, as it's going low... try one dot low.
4th shot 1/2" high, 1/2" left. Well that's pretty good, but want to be aiming 3 dots low at 10 yards to give a good point on range. So I added a 2nd shim of thin tin plate (the first had been added before last weekends testing). The tin plate is 0.01" thick. Then I tried again aiming 3 dots low.
5th shot, about 1" high and 3" left ...
Well it's obvious I can shim out the height successfully, but the left right adjustment is too prone to being knocked out of kilter every time I mess with the shimming. I've ordered another scope rail, so I can pin this to the wooden block for consistent alignment and then tighten it down with the screws.
I've since pinned the existing rail and ordered some 0.015" steel shim and another rail (oh the joys of E-bay)

All in all very promising, but it shows that I probably need to use slightly larger screws in some positions and possibly be using Loctite to secure them. I also need to regularly check everything for tightness.
Interestingly my brother recounted how his good quality gas power air rifle had drifted out of adjustment after a period of storage ... 1/2" out at 20 yards (I'd be happy with that on the crossbow!)

Wych Elm Shot In

I took the Wych Elm to be tested today by JD the guy who had brought me the stave, it had a good few dozen through it and was lobbing heavyish regular arrows over the 200 yards with ease. It'd be interesting to see what it did with an out and out flight arrow. It was declared to be a nice roving bow and as such I'll get it finished up. It would probably work nicely as a field shooting bow too.

I'd also taken the crossbow out to try and get some sight marks at 20 and 30 yards.
I was v inconsistent, possibly due to a bit of a back strain, which I exacerbated when pulling out an obstinate bolt.
On the plus side I picked a bag of blackberries.

String Jig

Here are some pics of my jig for making continuous loop strings.
Made from some scrap bits of Dexion, the vertical bit is welded on (badly) but could be bolted.
An S shaped hook of wire (clothes hanger) is also needed to pull one side of the loop down and out of the way while the other side is being served.
Note:- The scraps of string tied to the dexion is just where I've tied the string as I start to wind it back and forth along the jig. It then gets cut off or undone and tied to the other end to complete the continuous loop.

I've just shown one end for clarity, it also shows how the two main lengths bolt together for coarse length adjustment, it will do any string from a warbow to a crossbow prod.
The hooks for each end are wire tensioning bolts with the loops opened up shaped and smoothed.(Other brands are also available)
I may add to this post with more description and illustrations as a resource for people wanting to make one.
I know someone who made a similar jig using that 2 slot shelving support and brackets. (see pic right)
Note fine selection of books :-)

Ha, just found this old sketch from 2011, which may be helpful for anyone who isn't familiar with continuous loop strings.
I don't bother with the masking tape now that I have my jig and my bent wire S hook to keep the two sides of the loop separate
Note:- A couple of extra strands can be laid onto the string where the loops will be whipped, if some extra thickness is required. I do this for very thin flight bow strings which are only 6 strand.

Talking Out Of My Arse!

The patch is done and looks good... but what??? It's on the upper (right) limb???
What's going on??? The lower (left) was the weak one????
A bit of checking of my videos reveals I'd missed out a stage in my explanation, and I was, what's technically known as "talking out of my arse".
The full explanation:-
1. The left limb appeared to have a localised weakness (as seen on the video)
2. I re-heat treated that area, which improved it a bit.
3. Did some judicious re-tillering which got it looking even.
4. Noticed the thin sliver buckling at the pin knot on the edge (mistakenly assuming it was on the lower limb) and glued that.
5. Found the larger buckled area and did the patch.
6. Tiller check shows it looks much better (as per the end of step 3) but needs some tweaking still.


Now all this shows how easy is to get confused as to which limb is which and what you are doing.
I make no apology for this as it is part and parcel of bow making.
It also shows why I so often sprinkle my answers to questions with "In my opinion" and "I don't know, but I think..." etc.

I hope this makes everyone feel better about their mistakes and confusions :-)

Latest video:-
https://www.youtube.com/watch?v=alZi4fvO2p4&t=1s

Elm Tribulations

I got the limbs heat treated and the horn nocks done, which narrowed the tips and got the string line just right. Back on the tiller with it and I'm pulling to about 50-60- and the tiller looked horrid the left (lower) limb looked weak just right of centre. I was videoing at the time so you can see it, and hear what I thought.
https://youtu.be/0d1M4mHTpiw

I took it down from the tiller checked everything and it was the right way round ( I had wondered if I had some how reversed it!).
I did a little work to ease off the right limb and get the outers moving more... back on the tiller, looking much better.
Tidying it up some more I noticed a thin little sliver on one edge (about as thick as my thumb nail) had buckled up on the belly, there was a tiny knot on the edge of the bow there where it had started. I squirted some low viscosity super glue in under the sliver, unstrung the bow and bound it tight with rubber strapping while the glue set.
That fixed the problem nicely, I tidied the edge up put it back on the tiller, all was well, until I was again looking at the belly in that area. There seemed to be a blob of glue, or was it buckled wood? Yes, a thin area of the belly was buckling at that point. I was surprised as the bow is relatively low stressed being wide and thin. Had I overdone the heat treating? Was there an existing crack?
Only one way to proceed sensibly and that is to rasp out the area, (including the previous sliver and knot) and have a look.

Yes there is evidence of a crack, a faint line still visible in the rasped out area (running from about 2.5" to the 4" mark on the tape.

Final pic shows the prepared patch (heat treated) lying on the limb to check the fit.

Now this is just my opinion of the cause:- I think there was an existing split/crack /weak point caused when the stave was split.
IMO it shows the value of sawing rather than splitting wood where possible. Personally I'd rather harvest my own wood, but of course we aren't all fortunate enough to have access to every species of timber in profusion! Doubtless the man surrounded by Osage hankers after some  Yew and vice versa :-)
Some wood splits very clean, but even the with the most cooperative wood there will be tear outs and cracks that are generated by the splitting. This stave was pretty thin in the first place (hence the need to build up the belly at the grip)... was the split lurking there, waiting to annoy a bowyer or did it spontaneously spring into being?

In the top two pics you can just see the tiny knot on the top edge where the first sliver buckled up.

I'll update tomorrow when the glue has cured...