Shooting Machine Detail

I've had a request for some detail pics of the shooting machine.
It's theoretically simple, but because the bow is held at an angle (about 45 degrees) there are lots of weird angles.
Something that I screwed up with the mk1 is that I forgot to place the trigger mechanism up above the bow mounting (as in, the arrow passed over your hand... not through it!).
It also needs to have the main spine of the device set away from the bow and release mechanism to avoid the string slapping it (like it can on your arm). This is also why the track stops about a foot from the bow mount.
To stop the release mechanism sliding back when you are trying to cock the bow there is a magnet to hold it.
I made a wingnut spanner from a scrap of ply so that the A frame ( which fold up of course) can be tightened up solidly (bottom pic)
Care is taken to arrange the pulley so that it pulls dead in line with the release mechanism. Also the stirrup is placed so that pulling on the rope tends to force the front of the device down onto the ground rather than lifting it up.
I found it did flex a bit in use, so I added several blocks of plywood, glued in to stop flex and twist, these were just done on an ad hoc basis with a bit of quirky artistic interpretation to give it a steam punk / art deco look!
The main spine is a bit of 5 x 3/4 from an old bed frame.
The track is a slab of 3/4 ply for stability which is screwed on the the spine. The other bits are odds and ends of ply glued and screwed on to line up appropriately.
Enough chat, here are the pics.

Getting Close with the Spliced Yew

I took some video this morning, as I've put in a good amount of work getting the horn nocks fitted and the outer limbs blended in.
The draw length is coming back an inch at a time as I do more work.
Here's the video :- https://youtu.be/Vv2t3iYjL5g
Since then I've eased off the outers, blende the inner limbs into the thicker spliced grip and gone over it with a scraper, the draw length is now back to 25" at 60#.
The grip area has slightly thicker sapwood and a slight swell in the belly which gives a comfortable feel in the hand and maximises glue area. However, I'm keen to avoid a Victorian look with whip tillered or heavily elliptical tiller. I want the Warbow look, albeit a tad thinner as it's 60#

Starting a Spliced Yew Bow

I've been busy around the house and garden, but itching to get back to a bow... so, when yesterday Martin, one of the guys from Now Strike Archery got in touch after a 60# Yew bow, I was keen to get started!
Well I just happened to have this spliced stave that I'd made up ages ago and hadn't used as it was too good and big for a run of the mill 40# and too small for a full blown warbow.
60# is right in the Goldilocks zone, so I filed in some nocks and gave it a quick look on the tiller. I made a video here.
Here's a couple of pics showing how nicely the sapwood heartwood boundary matches up at the grip.

Having a good day... took some rubble and garden rubbish to the council tip. I got another coat of paint on the garage door early on before it started raining and thundering.
Done some on the bow and turned down the footing on two flight arrows that I'd glued up yesterday.
Emily Cat was missing all morning but eventually turned up soaking wet... proper towel job. Just gone out again even though it's still pouring! She's bonkers... Ah, just come back in... maybe not so daft.

Yew ELB Flight Bow Comparison

I've been doing gardening and tarting up the front of the house lately,so not much activity on my blog.
Today I went out and observed my mate JT testing the short Yew flight longbow (62.25" nock to nock) against his usual 120# Yew warbow which he uses for flight at the end of roves.
The 120 was shooting 32" arrows (actually 32.5" to the very tip) and the shorter yew ELB nicknamed " the bastard bow" 'cos it's bruised his bicep a couple of times was shooting lighter 28" arrows.
Well there was little to choose between 'em and in fact the warbow shot slightly further, mind it was a slight headwind and maybe the angle of launch was a tad high.
The conclusion was that the shorter flight bow wasn't really any better and so we might as well try drawing it a tad further and shooting one of the longer arrows to give a like for like comparison. This time it seemed to be a good 10 yards further.
Now a one arrow test isn't really fair, but it proved that there is more draw and poundage in the shorter bow, and that JT found it much easier to control at a longer draw (about 31" ? ).
Anyhow, I shall ponder long and hard about maybe heat treating the bow, and checking the tiller at 30-31". I shall also make up some 31" flight arrows using the one I shot as a reference.
I won't rush into anything...

Out of interest 31" draw from a 62" (1:2) bow is pretty much the maximum safe ratio* for a well made bow especially an ELB which works pretty hard.
* Obviously this can be exceeded but twice the draw length is a reasonable guide for bow length for an experienced bowyer.
Newbies should be looking at more like 2.5 times the draw length e.g 70" for a 28" draw.

Crossbow Chrono'

I'm back from a weeks holiday on the Dalmation coast of Croatia, gorgeous scenery, lovely warm sea to swim in. A little too much sitting on a coach at a border crossing, but it was all organised so generally very relaxing.

I deliberately hadn't chrono'd the crossbow prior to going as I didn't want any disappointment hanging over me! I finally got round to trying it yesterday evening, it had already had about a dozen shots through it and has had time to settle.
Using a commercial alloy bolt (303gn)
First shot 196.3 fps . I'd been expecting 200 +/- 10 so that seemed about right.
The brace height was a bit higher than I'd used before so I took about 10 twists out of the string and tried again... It was slower, so I then added 5 twists and repeated, and then the same again.
It doesn't take too many twists on a short bow to bring the brace height quite a bit.
Here are the results starting from the slowest where I'd taken off 10 twists.
184.9
186.7 (+5 twists)
190.7 (+5 twists)
195.0 (+5 twists)
192.0 (no change to string)
196.8 (no change to string)
193.4 (no change to string)

I didn't want to twist the string up too much and risk over stressing the bow as it seem to be working within it's comfort zone. But I couldn't resist trying a lighter bolt (198gn)
229.7 fps which is ok. If I take it field shooting I'll use the 303 gn bolts.

 I couldn't resist going on E-bay and ordering a 'scope. I only went for a cheapish one as this is all just a bit of fun. I meant to order one suitable for an air rifle as they for some reason seem to shake scopes worse than fire arms!
In the search for a suitable scope with a decent size lens to let the light in, not too much magnification (x2 is prob enough) and the right mounts, I forgot to check it was suitable for air rifles... I also forgot to check where it was being shipped from.... yup, you guessed China!
 Still I'll find plenty to do around the house and garden while I wait on delivery, and the scope was pretty cheap as it had an 8% discount on it so only £26.03 !
Specifications:
* Reticle Type: Mil-Dot 
* Illuminated Type: Red and Green with 5 level brightness adjustment 
* Magnification: 2-6 x 32mm
* Material: Aircraft-Grade Aluminum Alloy 
* Field Of View(@100yds/@100mm): 15.71-41.96
* Eye Relief(mm): 75.0-95.0 
* Exit Pupil(mm): 4.6-14.0
* Length: 210mm 
* Battery: CR 2032 x 1 (Not Included)
I'll include a link to it just in case anyone is curious, but of course it will expire at some point.
Scope

Tidying Up

I spent the morning sorting through the Yew which I got back in January 2017 . I got it all down and trimmed it on the bandsaw, created a whole lot of scrap and ended up with a few decent staves and some marginal ones and possible billets. I put 'em back up on the shelves, most of 'em are spoken for already and one that is otherwise lovely one has a huge sideways bend.

I've been repairing and making some more flight arrows with a bit of weight and stiffness variation. The differences are relatively small, but maybe a little extra weight stiffness and a more forward balance point will fly better in a  head wind... anyhow time will tell.
Pic shows my 28" flight arrows with a regular filed shooting arrow for comparison. (The one at the bottom is being fletched)
It's good to try and re-use ones with broken tips as they are a bit of a fiddle to make.

I haven't had the bottle to test the crossbow through the chrono yet.

Warbow & Crossbow

I've been working once a week mentoring my mate JT while he produces a warbow from a stave of Austrian Yew. He has 2 staves so, as is my wont we worked the worst one first, it had some sideways bend, one big knot and was a tad thin at the grip.
It's progressed nicely and is managing to pull 100# at about 24" . It needs the outers to come round now, but that will happen automatically to some extent when the nocks are fitted and blended in. Video here:-
Mean while the crossbow prod is ready for test... I'll update this post later.... fingers crossed.

The pic shows the string catchers / string bridges, they serve several purposes.
1. The stop the string riding over the top of the prod at the end of the power stroke. This can easily happen with a low brace height, string vibration and stretch.
2. They are made of horn mounted on sheet rubber which will hopefully kill some of the vibration and shock as the string hits home.
3. It improves the force draw curve, increasing early poundage as the bow is effectively shorter until the string lifts off the bridge. Another way of looking at this is that it is effectively allowing a longer string at the brace height. A longer string will pull back further (e.g. In the extreme limit a 30" string pulled back to double up on itself would be 15" long, but a 32" string would come back 16" ).
The Eagle eyed amongst you will notice the aluminium mounting plate has no hole for the bolt to travel through! That's just a blanking plate to allow it to be assembled and tested on the tiller. The actual plate that will be used is mounted on the stock and is an inconvenient angled shape so it can't be used for tiller testing.

The ends of the prod have been bound with carbon fibre/epoxy to prevent the string splitting down the end of the bow. The nocks have been double served, so hopefully it should be ok this time.

Whew, First test shot was good, the draw seemed pretty smooth and the shot didn't seem to clatter or rattle.
I put a load of wax on the track to show how far the string overshoots the brace position when actually shot.
Update:- I took some slo-mo video later to see how the string catchers work. It looks like they do a good job!
https://www.youtube.com/watch?v=LzVH8sQQkVo

... Just saw this little fellow in the garden... not a great pic as it was high up on the bush.