Hi guys sorry for any newb questions I did a search but could not find the info I needed.. I am having a lot of trouble with making prods.. I bought a trailer leaf spring today this one to be exact http://www.tractorsupply.com/trailers-towing/trailer-parts/other-trailer-parts/trailer-springs/carry-on-trailer-eye-to-eye-leaf-spring-1000-lbs-capacity-1750195 .. I took it apart and found that it was still extremely stiff and it didn't want to bend much for me try as I would.. So my question is what am I missing? Does it need to be cut? If so how do you suggest? I was thinking that if I cut it in half length-wise I would then have two sets of prods about 1 inch wide.. but then it might be to week.. So any help you can give me is much appreciated

Pellethuntr,

First of all, that thing is designed to work as a stack of leaves. If you take it apart, it will bend too much in the center.



I would....
-- cut the rolled mounting lugs off;
--cut the height of the spring down to about 1/2 or less at the tips, leaving a bit of extra material for the shoulders of the nocks. Cut from the bottom of the spring, so that the nocks will be above the center of the bow.

An idealized profile for a spring (a bow is just a "spring with a string") with a constant thickness would taper from its maximum height in the center to points at the ends of the limbs. This is obviously not possible for two reasons. First is that the nocks must have some height. Second, your spring has a big mucking hole in the middle. Therefore you will have to deviate from the ideal by leaving extra material for the nocks, and extra material around the center hole. If you don't leave more material around the center hole bow/spring will flex more in the center than elsewhere. This could well lead to premature failure in the middle.

By the time you have thinned the limbs, the bow/spring will be significantly "lighter" and more flexible.

Does this make sense? If not, I can try to post a diagram tomorrow.

Mac

A diagram would be great thanks for the reply Mac .. As far as the flex being in the middle, I was planning on cutting the spring in half where the hole is located and mounting the limbs separately.. I had another thought.. I was looking on Ebay at crossbow prods and I see that there are quite a few for sale in the 100-150 lb range.. If I return the leaf spring I will have about $30 back what do you guys think of these for a first hunting crossbow??

http://cgi.ebay.com/CROSSBOW-150-LBS-Prod-FIBER-GLASS-Replacement-LIMB-Sets_W0QQitemZ250777702538QQcategoryZ36100QQcmdZViewItemQQ_trksidZp5197.m263QQ_trkparmsZalgo%3DSIC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D250761573454%26po%3DLVI%26ps%3D63%26clkid%3D7314523630487961682

http://cgi.ebay.com/CROSSBOW-130-LBS-Fold-Up-MK-180-Prod-Replacement-LIMB_W0QQitemZ250777521539QQcategoryZ36100QQcmdZViewItemQQ_trksidZp5197.m263QQ_trkparmsZalgo%3DSIC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D250761573454%26po%3DLVI%26ps%3D63%26clkid%3D7314549873302091372

Pellethuntr,

The one piece fiberglass bow should work well. I've used the ones that Barnett sells.

I'm a medieval guy, so I would never think of using individual limbs. Perhaps someone else her can advise you about them.

Mac

I made a quick sketch of how I would cut that leaf spring, but I can't figure out how to attach it to a post.

Can someone help me here?

Mac

Thank you for the help again Mac.. I think I will be buying one of these prods soon.. The reason I like the two piece prod set is becuz the design I have in my head allows the prod to be perfectly in line with the track, basically the arrow will pass through the "center" of the prods.. like the one pictured.. I like the two piece prod set for that reason and becuz id like to be able to just un-string the bow and un-bolt the prods for easy take down and transport..

Here is a link to explain how to post pictures: http://thearbalistguild.forumotion.com/t2-posting-pictures-video-tutorial

Thats porbably a better explination than anything I can come up with quick.

When I try to follow those directions I get an error message at the point where I press the "host it" button.

Unable to create directories : /home/servimg/u/f72/16/22/66/39/

Mac

Hmm I haven't tried the "host it" feature. All my pictures have been located on photobucket. I wonder if you have to have a logon to Servimg.com to use that feature? I'll try to look into it when I get home.

Ok I have decided on buying my prods.. So no worries about your pic Mac.. Any one have any suggestions on which to buy?? either way I will be using a "split" limb design.. So I would like to use the 150lb prod for the extra fps, but im unsure if it would be ok to cut it in half?? Or I could just go with the 130lb any advice is welcome and appreciated

Bump.. could still use some help if any one has any suggestions

I would go with a more conventional sort of bow. If you go with two separate limbs you will vastly complicate the construction; all for a *possible* few more feet per second.

This is your first crossbow, yes...? Separate limb construction also significantly increases your chances of structural failure. Make your first foray into crossbow construction simple. You can do something higher tech on some later bow.

Mac

Hi Pellethunter,

Mac has a point there.

Risers are kinda on the advanced crossbow building end, however it's not impossible.

The pro's and cons of riser/no riser:

	Riser (Split Limb / Full Limb)	No riser (Full Limb)
Weight	Crossbow is Front Heavy	Light front end
Compactness	Wider prod(limb) for the same draw length. Limb(s) need to be longer to account for mounting seats.	Shorter prod can be used to get the same draw length as the mounting space is minimized allowing a better part of the limb to work(bend)
Limb system suitability	Risers can be designed with different limb angles(from parralel to past parralel) and can even be designed for an adjustable limb angle and thus can be used both with the bare limbs(D-bow or recurve) or compound assemblies(cammed limbs).	Mainly used with bare limbs. However crossbows with a compound limb mounted under an angle have been spotted on the outskirts of Russia
String Friction	Less to none. String travels straight whether track is present or not. Take care when cutting string nocks as that is one of the elements that is responsible for string height	More. Varies with prod mounting angle and string thickness. More about mounting angle troubles here...link
Ease of construction	Moderate to Advanced - Special tooling and materials may be required depending on the design.	Easy to Moderate - prod can be mounted straight to stock/rail. Cutting a seat with proper mounting angle and stock reinforcement issues seem to be the only major points...the rest lies with the bow "design" and mounting options.
Mounting	Special care should be taken when mounting risers as great amount of torque is produced. May require a mounting block bolted to the stock or incorporated into the front end of an arrow track.	Force is directed along the stock axis. Can be cord bound or mounted using bow irons. May require a reinforcement bolt to keep the stock from splitting with heavier weight bows.

If I missed something or am mistaken, please correct me...

A riser can also be used with a single limb.

One example where limbs are below the track level is Taiwanese crossbows that press the limb in the center with one bolt using a small steel plate as a spacer(not to harm the limb).


And another version that is with a shoot through single limb...more about it here Crossbow Books - Match Target Crossbow Article


The most basic riser I can think of is a piece of angle iron as in the picture...only iron mounted backwards and/or with limbs mounted on the outside to keep the pressure on the riser rather than just the mounting bolts (Pavise explained it here>>>link)



About leaf springs...there is an old article that might help you a bit with the tillering(adjusting limb proper bend)

http://www.vintageprojects.com/archery/crossbow-leaf-spring.pdf

...as well as a great crossbow building resource by basileus that also speaks of using leaf springs.

http://thearbalistguild.forumotion.com/t276-good-page-on-construction?highlight=great+page

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Pellethuntr wrote:...I had another thought.. I was looking on Ebay at
crossbow prods and I see that there are quite a few for sale in the
100-150 lb range.. If I return the leaf spring I will have about $30
back what do you guys think of these for a first hunting crossbow??

http://cgi.ebay.com/CROSSBOW-150-LBS-Prod-FIBER-GLASS-Replacement-LIMB-Sets_W0QQitemZ250777702538QQcategoryZ36100QQcmdZViewItemQQ_trksidZp5197.m263QQ_trkparmsZalgo%3DSIC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D250761573454%26po%3DLVI%26ps%3D63%26clkid%3D7314523630487961682

http://cgi.ebay.com/CROSSBOW-130-LBS-Fold-Up-MK-180-Prod-Replacement-LIMB_W0QQitemZ250777521539QQcategoryZ36100QQcmdZViewItemQQ_trksidZp5197.m263QQ_trkparmsZalgo%3DSIC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D250761573454%26po%3DLVI%26ps%3D63%26clkid%3D7314549873302091372

That #130 limb set isn't powerful enough...it's good for target shooting with light small diameter aluminum shafts, but anything heavier bounces off the target...just my personal experience.

As for the #150 prod...I've been on and off building my younger brother a crossbow for hunting small stuff...don't have any up to date pictures since I started making videos, but there is an older photo with a piece of angle iron and wooden wedges as mounting(couldn't wait to test the trigger )



...at around 14" draw (probably the limit with that prod) that things packs a punch...who would have thought some #20 would make such a big difference.

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