Crossbow Design Perversions - Or are they?

Inspired by the ideas of one of my fellow crossbow fascinated friends I bring you "Crossbow Design Perversions". Over the years crossbow has evolved and managed to develop some interesting lever/limb/trigger/stock systems and is still evolving at an insane rate.



I've met lots of people who have these crazy ideas...well...actually they were considered crazy until similar designs showed up on the market. All Inventors, Beginners and Professionals, Theoretical and Practical alike - I Welcome You!

Images - Igora > Crossbow Perversions > Russian Crossbow Building Community

Good afternoon.
Thanks IVO. It is very pleasant to see here my old drawings.
Originally they were drawn as an example of "distortions". But it appears people who like to think out such "distortions", is present much. And it is a lot of from such ideas later appears in real products.
This forum is the young. The participant it is not a lot of. But I hope that this forum, such people, also visit:). So there will be a theme for interesting conversation.

Here one more drawing. November, 2006 . And 3D model made Casido, on this drawing.
It is very interesting to hear opinion on it other people.

I apologise for the automatic translator

Добрый день.
Спасибо IVO. Очень приятно увидеть здесь мои старые рисунки.
Первоначально они рисовались как пример "извращений". Но оказывается людей, которым нравится придумывать такие "извращениями", присутствует много. И много из таких идей позднее появляется в реальных изделиях.
Этот форум молодой. Участников не много. Но надеюсь что этот форум, такие люди, также посещают. А значит будет тема для интересного разговора.
Вот еще один рисунок. Ноябрь 2006 г. И 3D модель сделанная Casido по этому рисунку.
Очень интересно услышать мнение о нем других людей.
...
Извиняюсь за автоматический переводчик

Hello Igora,

I'm very glad to see your ideas on display here and up for discussion...I have had a few crossbow "perversions" of my own, but we'll talk about them a little later as there is a very interesting idea already present.

I like others have tried testing a few designs before and see that miniatures are great for doing exactly that...so I went out and bought some plexiglass plastic and should have a few basic models for testing and comparing soon...What I have on my mind is reproduce the design in plastic and then record the FD Curve while drawing it to full draw to help me understand how it works. I have a few thoughts on benefits that this model has over a few others, but I'd like to make the models and "feel" how they worn in this combination.

...I was also thinking of comparing it with a few more traditional/(accepted by market ) designs as well as the few new ideas that have hit the market and now becoming more popular not only amongst consumers, but crossbow craftsmen like us as well...giving us a double edges sword of crossbow building...lets swing it!

I'll be keeping you informed of my progress. Once again thanks and I'm glad you are here with us sharing your ideas and experience...I'm sure this topic will be entertaining as well as informative to us all.


Привет Igora,

Рад видеть что твои идеи выставлены на обсуждение...есть парачка свих извратов, но поговорим о них чюток пожже так как стоящяя иде уже перед нами.

Я как и другие когдато пробовал протэстировать некоторые дизайны и решил что миниатьры/макеты это самое то...так я пошел и купил пару листов пластмассы типа плексиглас и думаь что за несколько дней управлюсь в изготовлении макетов нескольких простых моджлей для тестирования и сравнения...у меня на уме сделать данную модель и постепенно натягивая начертить динамическю кривую сего апарата. Есть несколько мыслей о позитивных сторонах этой системы по сравнению с другими, но я сначяла хочь сделать несколько модэлей и прочювствовать как они работаьт в такой компоновке.

Я еще думал сравнить этот вариант с более традиционными(уже принятыми маркетом) дезайнами и несколькими новыми что только начинают вылазить на магазинные полки и найинают нравитса не только покупателям, но и нашим арбалетостроителям как мы...что дает нам двух сторонний меч арбалетостроения...так взмхнем же им!

Я буду держать вас в курсе событий. Еще раз спасибо и я рад видеть тебя сдесь делящегося своими идеями и опытом...Я уверен эта тема будет как веселая так и познавательная.

The decision of a problem of synchronisation of blocks

Geezer here with a comment: I enjoy the automatic translator. It gives a literal translation rather than make a smooth, idiomatic one but that's part of its charm. That way I get an idea how the concepts go together in a language I wouldn't otherwise understand. Hooray for the auto-translator, with all its faults. It is better than not knowing. Geezer.

Igora wrote:The decision of a problem of synchronisation of blocks

Strings will pull right limb more backward and left limb more forward.. I
think this one will work better with a smaller cam in a middle (smaller
cam generates less directional disturbances on a limbs).
Also, this system won't provide any synchronization of limbs. As I
suspect, one limb will tend to bend more than other especially with a
"hard" cam..
That's why I think binary cams are still better..

Здесь тетива будет тянуть левое плечо немного вперёд а правое немного
назад. С блоком меньшего размера эффект конечно уменьшится..
Еще, система не даст синхронизации плеч, и я подозреваю, что одно плечо
может сгибаться больше другого даже при малом дисбалансе, особенно с
агрессивным блоком..
Поэтому система всё-таки не лучше бинарных блоков..

Geezer wrote: ... Hooray for the auto-translator, with all its faults. It is better than not knowing. Geezer.

Yes.  

Regerald wrote: Strings will pull right limb more backward and left limb more forward.. I  think this one will work better with a smaller cam in a middle (smaller  cam generates less directional disturbances on a limbs)...

Yes - certainly there is such moment. And it is interesting to check up, how much it is reflected in work. Да - конечно есть такой момент. и интересно бы проверить, насколько это отразится на работе.

Regerald wrote:... Also, this system won't provide any synchronization of limbs. As I suspect, one limb will tend to bend more than other especially with a "hard" cam ...

It will seems to me of it not. From the small block of a cable are fixed directly for a limb. Therefore the slightest movements of one limb will be reflected in block turn. And consequently and on the second limb.  мне кажется этого не будет. Ведь от малого блока троса закреплены непосредственно за плечи (жестко). Поэтому малейшие движения одного плеча отразятся на повороте блока, а следовательно и на втором плече.  

Regerald wrote:...That's why I think binary cams are still better...

Probably  ...  But in my opinion. For independent manufacturing, it to make than the presents binary more well
 возможно  ...  Но по моему мнению, для самостоятельного изготовления, это будет доступней сделать чем настоящие бинарные  

PS Regerald, можно спросить. Вы кажется английский достаточно хорошо знаете.   Limb и Плече - это одно и то-же? а то переводчик мне усилено shoulder предлогает

Igora wrote:

Regerald wrote:... Also, this system won't provide any synchronization of limbs. As I suspect, one limb will tend to bend more than other especially with a "hard" cam ...

Therefore the slightest movements of one limb will be reflected in block turn.


PS Regerald, можно спросить. Вы кажется английский достаточно хорошо знаете. Limb и Плече - это одно и то-же? а то переводчик мне усилено shoulder предлогает

But slightest imbalance in a limbs can provide a drift of a central point of a string. Nothing prevents it, as I see.. Am I wrong?
Но даже небольшой дисбаланс в плечах уведёт центральную точку тетивы вбок от зацепа. Ведь этому ничего не препятствует, как я понимаю.. Или я что-то упустил?

//automatic translator translates "limb" as a "shoulder", "cam" as a "block"//
Да, термины он неправильно переводит. Shoulder - плечо человеческое.
Limb - плечо арбалета. Так-же "блок" по-английски "Cam", дуга - "prod"

Regerald wrote: ... But slightest imbalance in a limbs can provide a drift of a central point of a string. Nothing prevents it, as I see.. Am I wrong?
Но даже небольшой дисбаланс в плечах уведёт центральную точку тетивы вбок от зацепа. Ведь этому ничего не препятствует, как я понимаю.. Или я что-то упустил?

It will be prevented by that is allocated by the red. It is rigid communication between limbs.
Этому воспрепятствует то, что выделено красным. Это жесткая связь между плечами.

Regerald wrote: ... //automatic translator translates "limb" as a "shoulder", "cam" as a "block"//

Thanks

Igora wrote:It will be prevented by that is allocated by the red. It is rigid communication between limbs.
Этому воспрепятствует то, что выделено красным. Это жесткая связь между плечами.

Damn, you were right.. I just understood this system in a wrong way.. Limbs are absolutely synchronized.
By the way, is there any idea how to solve the problem that cam and a bolt groove are in a same plane?
Да, вы были правы, я сначала просто неправильно понял работу системы..
Кстати, есть ли идеи как решить проблему расположения блока и канавки для болта в одной плоскости?

Hiroballistra, with Eccentric Cam


Triggers

I've been slacking again...well on the crossbow side of things at least.

There is an interesting video floating around on the net showing a wicked little lever bow called Survival Flipper.

Technically it's a "lever based compound slingshot" since it uses rubber bands powering a set of inward swinging levers through series of idler wheels(rollers). It makes no sense now, but here is a vid that will make sense of all this.

I've occasionally stopped by some other weapons forums and here's who I came across upon posting a video of the flipper.



An awesome "little" build(this thing is huge) this guy was doing and a
few suggestions regarding the trigger made it simply bad-ass!



The draw
length looks to be over 30" and probably drawing around 20-25lb(drawn with two fingers )

Cool little build...lever crossbows live!

ok,, the first thing that raises concernes with me is this: why the @#$#@ is he using RUBBER BANDS,, why doesnt he use an iron spring or something,, it is much more durable than some rubber bands tied together and mounted on that thing.
I have seen this kind of bow before on sinza's forum,, it is a pretty neat design and stuff,, but can it be more compact? I think his greatest challenge right now is to make it smaller and as powerful as it is right now.

Springs vs. Rubber bands is not a single answer question.

I tried putting together a comparison chart, but they are just too different in their nature, here goes my try.

Spring:

• Heavy (slower, but better for accelerating heavier projectiles/assemblies)
  
• Durable (takes shock well, occasional dings and minor scratches have no effect on performance)
  
• Better weather resistance (withstands elements like UV light, moisture, natural temperature changes and with various protective coatings and treatments can be even more weather resistant)
  
• Longer Life (takes repeated use well, but again it's not indestructible and can crack or take set/stretch over a period of time especially if left stressed for an extended period of time....we are talking days)
  
• Consistency of energy storage (not many elements will have a significant enough impact on the springs performance and thus it will maintain consistent energy storage making use of sights possible)
  

Rubber:

• Light (fast, better at accelerating relatively light weight projectiles/assemblies)
  
• Brittle (shock is not a problem since it's absorbed by rubber, but even the slightest scratch/tear render the bend useless as it deteriorates more and more with every single use)
  
• Bad weather resistance (UV light makes rubber more brittle, moisture content is important - rubber dries up, temperature changes effect the elasticity of rubber making it stiffer if temperature is lower or more elastic if temperature is greater)
  
• Short life (with all the factors combined...it is evident that rubber degrades with weather and repeated use)
  
• Consistency (temperature and moisture content play a great role in rubber's performance, energy storage for a given stress will vary with temperature/moisture, rubber also loses some of it's power if left stressed for even a short period of time - we are talking minutes....thus resulting in inconsistent energy storage in different environments and sights will have to be adjusted frequently and perhaps not always necessarily)
  

There is also a Composite (fiberglass for example) which has some advantages over both as well as some weaknesses.

• Relatively Light (Lighter than steel, heavier than rubber...a balanced material good for accelerating mid weight to heavy projectiles/assemblies)
  
• Relatively Durable (Not very shock resistant, dings and scratches can be a problem in the long run...rubberized coatings can help protect the surface from damage)
  
• Weather Resistant (UV light can have a shorten the life of a composite and protective coatings have to be used to prevent that, moisture has no effect on composites, temperature slightly effects the performance of a composite)
  
• Long life (Modern composites take no noticeable set if any at all, can be left stressed for long periods of time)
  
• Consistency (Since it takes no set, can withstand repeated use and long stress periods better than steel and rubber, keeps it's energy storage properties in a variety of environments - consistency is at it's best and use of signs is at it's most accurate)
  

Just a few things off the top of the head.

To return to the original question...Rubber is inexpensive, widely available, and easily adjustable to a variety of applications, a bundle of various thickness can be collected to adjust power.

An inexpensive material, good for quick projects I guess.

---

As for compactness and improved efficiency...

There have been a few things mentioned about lever bows.

When taking The Flipper as a platform to improve on...the first thing jumping to mind is allowing the levers to be bent past the point where they are perpendicular to the stock. This will allow for longer draw and thus a more compact version will be able to draw as far as the bigger one. Also the shorter levers will be lighter and will swing faster.
Another thought that came across in the few discussions I had was to recurve the short lever arm which would achieve a similar effect to the one explained above - winding the string/bend in a smoother fashion and thus theoretically resulting in a smoother shot. An even more compact and even more efficient version would have cams instead of the shorter lever arms, which if calculated correctly will give a force draw curve similar to compounds where energy transfer will be close to maximum every inch the projectile accelerates >>> similar to what Igora did in his ballista design.

---

Now for compactness during storage/transportation...there has been a few things said and they have all landed in the same bucket. The bar on which the levers are mounted can be split in two and made to fold forward and locked. Kinda what our buddy Clyde did with his little bow.



Though again, any kind of mount for folding limbs will make the assembly heavier and more demanding as it's made more powerful...winning in compactness, but adding weight.

Ivo

ok,, that's a very nice answer,, and very long too
I will read it tomorrow for the second time,, because I can't really read after a few beers..
the basic line is I guess that it depends on the project, what kind of material you use.
thanks for the reply
Serafim

I got a friend, he's an accountant, and he drinks all the time...seems to be he becomes a human calculator when he does.

Hmmm, maybe you shouldn't drink if it reduces your ability to reason and/or impairs your vision....not exactly a "forum mode"...don't you thing?

Just a thought.

Ivo

haha yeah,, I normally don't drink on workingdays, but i just felt like it so..
well,, the point is that I can still receive information and reason with it,, but then there are just like a thousand other thoughts going through my head that my memory is really REALLY short so..
ok, I'm going to swear on it.
I swear on my first pocket knife that I wil never EVER drink before going to this forum.

there you go
I still think rubber bands are lame though, but that's just my opinion. It is his project so he should do whatever he wants with it
greetz
Serafim

I cant even fix my basic slingshot DDX So I have no clue on how you made that DDDX I am such a loser and an epic fail at life.

A spring gun/bow idea...do we need sticky out bits.. with this double pulley system there is a 3:1 mechanical advantage..so you need a very powerfull spring to give a final tension of 100+ .. as a compensation the draw is longer than normal so the arrows acceleration continues for longer.

A small model made to test the mechanism works fine..

Igora wrote:The decision of a problem of synchronisation of blocks

Jennings "UniCam"(tm)
http://www.archeryhistory.com/compounds/pics/80/bear50.jpg

from 1987


http://www.emeryloiselle.com/2008_photos/jennings-unistar-13.jpg

My own version of the rubber band flipper. It uses multiple #64 cheapo rubber bands from Walmart for variable power. Max I've tried so far is 17 per side (in picture) and fires standard arrows pretty fast and accurate. I have yet to chrony it as I don't have access to one yet. It's made of 3/4" aluminum square tubing and the arrow holder is PVC pipe with aquarium clear tubing with copper electrical wire inserts for adjustability.

Looks neat ! something that I've wanted to make for a while now. I like it!

Great job and imagination！Hope for real products.

Have not seen this thread before.

Like the simple external trigger claw mechanism at the top of the page!
Looks super simple to make