The Arbalist Guild

Would you like to react to this message? Create an account in a few clicks or log in to continue.

Crossbows - Everything about Building, Modding, and Using your Crossbow Gear

Latest topics

» Chu Ko Nu - repeating chinese crossbow
by c sitas Today at 8:30 am

» Ball shooting Crossbows worth the bother
by topfmine Wed Sep 15, 2021 3:24 pm

» Skew of tiller
by drawknife Fri Aug 27, 2021 9:18 am

» tiller desgin
by crusader Wed Aug 18, 2021 10:37 am

» Want to build modern target crossbow
by ora8i Fri Aug 13, 2021 1:20 pm

» starting a 1400's replica
by tghsmith Wed Aug 11, 2021 10:25 am

» New Medieval just about finished
by Dark Factor Mon Aug 02, 2021 6:41 am

» How do I tune this
by stuckinthemud1 Sun Jul 25, 2021 3:14 am

» Plans and materials for my first build
by c sitas Sat Jul 03, 2021 7:39 am

» Bolt rest
by stuckinthemud1 Mon Jun 14, 2021 3:24 pm

» Collotiere a Charavines crossbow
by stuckinthemud1 Sun Jun 06, 2021 2:25 pm

» ash lath and pin-lock crossbow
by stuckinthemud1 Wed Jun 02, 2021 7:56 am

» Late medieval tournament distances?
by stuckinthemud1 Thu Apr 15, 2021 8:20 am

» Cutting delrin straight by hand?
by kenh Thu Apr 01, 2021 8:24 pm

» Other forums like this one?
by stuckinthemud1 Tue Mar 30, 2021 9:23 am

» new find in china, terra cotta warrior site
by tghsmith Thu Mar 25, 2021 4:42 am

» Crossbow Books
by Andy. Sun Mar 14, 2021 3:46 pm

» 95lb ancient crossbow shot faster than 960lb medieval
by Fangbows Fri Mar 12, 2021 11:36 pm

» best type of horn to use..
by kenh Tue Mar 09, 2021 3:16 pm

» re-introduction
by tghsmith Sun Mar 07, 2021 3:15 pm

» 4 fletch question
by 8fingers Fri Feb 05, 2021 3:14 am

» fix bolts
by MPDVM Tue Feb 02, 2021 7:40 pm

» Reverse draw compound bow build
by c sitas Tue Feb 02, 2021 7:20 pm

» New Build for 2020
by Gnome Wed Jan 27, 2021 6:19 am

» Spanning bench ideas
by stuckinthemud1 Fri Jan 08, 2021 1:07 pm


5 posters

    ramped tables

    Geezer
    Geezer
    Master Crossbowyer
    Master Crossbowyer

    Posts : 1194
    Join date : 2010-01-12
    Age : 73
    Location : Austin, Texas, USA

    ramped tables Empty ramped tables

    Post by Geezer Fri Mar 05, 2010 6:56 am

    Geezer here, with a fresh observation. Whereas most of us go to a lot of trouble to make our bolt-track/table straight and slick, I have observed a fair number of medieval/renaissance crossbows that feature a ramped track. Lightweight Spanish bows often have no bolt-groove at all for the first inch or two ahead of the lock. The groove starts there and gets progressively (but not very) deeper as it goes forward. Of course many of those fat Germanic sporting bows have no groove at all, but shoot off an inlet bolt-rest. Note that a bolt-rest that is TOO high will result in your bolt porpoising in flight, just as a rest that is off center will make your bolts yaw or even whirligig in flight. Generally I try to discourage my customers getting the rest in mortise, since the blasted things get knocked off regularly and I'm constantly replacing them, particularly for people who never mind their brace-height. For people who want un-grooved bows, I prefer to provide a simple ramp at the head with a bit of groove cut into it. (a fairly common feature in nordic bows)
    Some bows simply have a rising bolt-track, particularly at the very end of the power-stroke. If you do that right, it should give your bolts a little loft, resulting in a slightly longer point-blank range, and maybe that was the whole purpose back in 1500, but I have another theory: Perhaps the ramp is intended in extend the useful life of laminated horn/sinew composite prods. I figure any bow that you have to glue together will eventually come apart, due to a combination of flexing and shock of un-tapped energy absorbed at the end of the power-stroke. So if the bolt-track ramps upward at the end of the string-run, you Should get a slightly softer stop, as the friction increases, with less recoil and noise. Of course that means you're wearing the center-serving a bit more and twisting the prod a bit, but it should soften the shock as the string halts the prod, and that might be critical in a prod glued up with fish-glue.
    Of course if the ramping starts too soon, you lose a bit of energy at the end of the power stroke, but I suspect most crossbows and handbows for that matter, don't get much push from the last 20 percent of the power stroke anyhow. Maybe it was worthwhile to sacrifice that last bit of push in favor of longer life for a Very Expensive horn/sinew composite prod. So does this have application to modern laminated bows as well?
    Just a thought... comments? Geezer
    Pavise
    Pavise
    Dear Friend, You will be Greatly Missed.
    Dear Friend, You will be Greatly Missed.

    Posts : 128
    Join date : 2010-02-07

    ramped tables Empty Re: ramped tables

    Post by Pavise Fri Mar 05, 2010 10:31 am

    Hi Geezer,

    Some very valuable observations and comments as usual my friend.

    I have plotted the path of the string and prod by using scaled drawings, and depending on their vertical location in the stock, the limbs do indeed twist as they seek alignment with the directional forces and back again upon release. Keeping frictional losses at a minimum is one of our goals and as you point out there are many examples where this has been explored by various makers. The "ramp" you describe reminds me of the launching deck on aircraft carriers where a final lift ramp forces the plane up and away. I am now thinking that a grooved but ramped crossbow deck, that only acts upon the string, would help towards retarding unwanted harmonics and repeated oscillations before the string finally comes to rest.

    Pavise
    kiltedcelt
    kiltedcelt
    Tinkerer

    If there is a will, there is a way.


    TinkererIf there is a will, there  is a way.

    Posts : 91
    Join date : 2010-02-17

    ramped tables Empty Re: ramped tables

    Post by kiltedcelt Fri Mar 05, 2010 12:35 pm

    Geezer,

    Do you have a picture or two of this feature that you could post, either from your bows or historic examples? I'm having a little trouble visualizing it.
    Basilisk120
    Basilisk120
    Moderator
    Moderator

    Posts : 548
    Join date : 2010-03-01
    Age : 42
    Location : Arizona

    ramped tables Empty Re: ramped tables

    Post by Basilisk120 Fri Mar 05, 2010 8:08 pm

    I believe this is what he is talking about. This is a crossbow that was made by Lightly.
    There were taken with my phone quickly so sorry about the poor quality.
    ramped tables 2010-03-05195752

    ramped tables 2010-03-05195752

    ramped tables 2010-03-05195736-1
    kiltedcelt
    kiltedcelt
    Tinkerer

    If there is a will, there is a way.


    TinkererIf there is a will, there  is a way.

    Posts : 91
    Join date : 2010-02-17

    ramped tables Empty Re: ramped tables

    Post by kiltedcelt Fri Mar 05, 2010 11:41 pm

    Okay, that's kinda what I was envisioning from the description. Is this mainly seen on earlier bows - particularly the ones with horn/sinew prods?
    Geezer
    Geezer
    Master Crossbowyer
    Master Crossbowyer

    Posts : 1194
    Join date : 2010-01-12
    Age : 73
    Location : Austin, Texas, USA

    ramped tables Empty ramped tables

    Post by Geezer Sun Mar 07, 2010 6:29 am

    Are ramped tables mostly a feature of horn/sinew composite bows? I believe that is the case, but not invariably so. Geezer
    Lightly
    Lightly
    Master Crossbowyer
    Master Crossbowyer

    Posts : 199
    Join date : 2010-01-12
    Age : 61
    Location : Austin, Tx

    ramped tables Empty Re: ramped tables

    Post by Lightly Sat Mar 13, 2010 10:15 pm

    Basilisk and Kiltedcelt;

    I could not find a photo of a ramped bow amoung my photos, however, I DID find a photo of YOUR Ramped bow, Basilisk, just before you bought it, at Estrella.
    http://www.flickr.com/photos/swifthoundbows/4430546999/in/set-72157623490983579/
    The dark portion at the top of the bow is the ramp, with the photo being face on, you cannot tell that that bit gradually rises to the tip of the bow.
    I don't have any right now to take a photo of, but I will have a look in the shop when we get back.

    Best!

    Lightly

    PS
    Basilisk, in that Flickr set, there are a couple of photos that I took as I replaced the prod on your bow....

    Sponsored content

    ramped tables Empty Re: ramped tables

    Post by Sponsored content


      Current date/time is Fri Sep 24, 2021 5:22 pm