inertia arrow rest

[geoffretired]

I started making an inertia drop away rest. The workings became so fiddly that I changed it to a drop away driven by the cable slider. In my research I contacted different rest manufacturers in US. I had noticed two different takes on the time of the drop. One side said their arrow rest stayed in contact with the arrow until the last mm or two before the fletchings passed.
Others, obviously, were dropping as soon as possible. I found this difficult to accept unless there is a case for both situations to exist and be successful.
The long contact was explained as, " guiding the arrow for longer, like a rifle barrel guides a bullet longer than a short barrel pistol"
The quick drop take was not explained (no reply to my enquiries)
I can guess that the quick drop theory is saying something like; less time on the rest means less chance of disturbing the arrow once it has started, and it is bending etc so give it some freedom.
I imagine the rest could drop too soon; before the arrow has sufficient speed to direct itself without support.
There is a similar difference with the springy lauchers. Some set them as weak as they can get away with, others are quite stiff in comparison. Is this really part of the same thing?
I am still curious as to the correct method for launching arrows from the rest.
Is there a scientific or mathematical ideal that can be satisfied by more than one solution?

[Rik]

Springy launchers:
The principle is the same as with a flip rest, you want as little pressure as consistently holds the arrow up. In an ideal situation, there shouldn't be any late contact with the rest, but if there is, you want it to move as easily as possible.

Drop away rests:
There will come a point where the arrow doesn't need support. You see that in high speed video of a release. I don't know how you determine what that point is, though I'd guess there is a rule of thumb that may be applied. The "guiding the arrow" explanation is specious IMO. If your arrows need that much interference, there's something wrong with your setup. I think the "leave it to the last minute" approach is probably just over-cautious.
It occurs to me: if you leave the drop very late, how quickly does the rest fall? Does it just end up behaving just like a springy rest in that case?

A bit of high speed video would be great here Geoff. As I see it the arrow floats in mid air quite soon after launch. A bit of + nock hight gives the arrow chance to clear the rest. It seems most compound archers favour a rest with just enough tension to hold the arrow up at full draw. I set mine to sag when the arrow is half way down the draw. I'm not keen on drop away rests as it's just something else to break down just when you don't want em to.

[geoffretired]

Thanks Rik and Rich,
Both of your inputs have cleared things up in my mind. I feel unhappy about guiding the arrow too far, especially as it is not flying in a straight line.
It would be very like the normal springy rest, except the fletchings would clear.
For those who set the nocking point high, there would be no advantage either as they have good clearance by design.
I appreciate the idea that simple is best as there is less to break. My interest in making things just takes over and I have to run with the addiction. I have shot hundreds of arrows from mine and found out the weaknesses. Those have been strengthened. All the moving parts are stronger than necessary, I hope
What attracts me to the idea is that I can get close to ideal launch angle without having to worry about the fletchings catching. I built in an adjustment so the time of drop can be changed. Give it too much delay and all hell breaks loose when viewed with a paper test.
My latest, is to make a hydraulic resistance for the trigger of my release aid.
It will, when finished, allow continuous squeeze but will stiffen if punched.
It may give me some security while going through the rehab.
Thanks again for the help.

Originally Posted by geoffretired

My latest, is to make a hydraulic resistance for the trigger of my release aid.
It will, when finished, allow continuous squeeze but will stiffen if punched.
It may give me some security while going through the rehab.
Thanks again for the help.

Hmmm a bit like the fluid/solid properties of "cornflower"? Food for though, pardon the pun.

[geoffretired]

Does cornflower have fluid/solid properties?

Originally Posted by geoffretired

Does cornflower have fluid/solid properties?

Go down to Morrisons/Tesco, buy some. Mix it with water. In the bowl it will be liquid stir it slowly and it will remain fluid, stir it faster and it will stiffen up. Punch it and you will hurt your hand. Strange stuff Cornflower.

[geoffretired]

Could I use it in my hydraulic damper?

Originally Posted by geoffretired

Could I use it in my hydraulic damper?

I have no idea? Your the inventor Geoff, get experimenting. Honestly try it, it's really odd the way it stiffens up with agitation/violence. It is worth looking into.

[geoffretired]

I've made the equivalent of a mini sized shock absorber. I'll fill it up and see what happens.
Thanks