Cranequin the maximum draw weight.

What is the maximum draw weight of a cranequin on a medieval type crossbow. This past summer in Germany somewhere there was a get together of area shooters. A member from Sweden a Mr. Halvslak sent back some really cool video of the competition. I notice on the video many of the shooters where using a cranequin to span their weapons. Does anyone knowhow many pounds of draw weight that a cranequin can handle.

What's the maximum draw weight for a cranequin? It depends on the cranequin of course, but potentially it's lots and lots. The most powerful bows I have seen are fitted for cranequins, including the big siege-bow at the Kunsthistorisches museum in Vienna.
To be on the conservative side, let's say well over a thousand pounds, IF the cranequin is built right. Geezer.

Geezer: First off I got a lot of compliments on the crossbow you made for me. What I'm talking about is not a siege but a regular hand held one. Stock in the range of 25> 29 inches long. There is a bow on the Mutal of Poland web site with a cranequin. So it's not on heard of to have a crossbow that has the power to draw 400lb> 500lb. How on the metal type or grade to be used in making a cranequip to handle that type of spanning requriment. All kinds of questions are popping into the brain now . Gear ratio used in the application to draw back (lets say 8 inches) from resting point to lock and load the nut. I would enjoy a dialog on this subject. Thank you Dave for answer.

Michael: Some years ago, I built a very nice crossbow for a customer who wanted it fitted with a Matuls cranequin. The bow wasn't stout enough to require the cranequin, but it worked out very well indeed. At that time, Matuls offered two cranequins, one for lighter and the other for heavier bows. As far as I could see, the only difference was the mounting for the heavy cord loop that fits over the cranequin-pins a short distance behind the roller-nut. The lighter cranequin might fail there, where a stronger mount would accomodate a very strong bow. How strong? I DON'T REALLY KNOW.
YOU CAN FIND DETAILED DRAWINGS IN PAYNE GALLWEY'S "THE CROSSBOW" AS WELL AS IN PATERSON'S "A GUIDE TO THE CROSSBOW" HARMUTH'S "DIE ARMBRUST" AND MANY OTHER SOURCES. IF YOU FOLLOW THEIR PLANS CLOSELY, YOU SHOULD BE ABLE TO FABRICATE A CRANEQUIN THAT WILL HANDLE HUNDREDS OF POUNDS SAFELY. BEYOND THAT, I CAN'T SAY. MAYBE MAC, OR ONE OF OUR OTHER METAL-GURUS COULD GIVE YOU SOME GUIDANCE HERE. I CANNOT. GEEZER

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Michael: Sorry about the all-caps, my keyboard went nuts, and I neglected to check before sending. Anyway, I'm not in the habit of shouting. Geezer.

Geezer: Thanks alot. When a stock is made to handle lets say a 500lb draw weight crossbow: ( the 500lb is just for conservation only) does one have to beef up the stock in places. Then would one have to use a steel roller nut.

I have had the opportunity to examine some strong steel crossbows, both "German" patterns, one 16th century and the other a Johan Harnish Saxon bow that might date as late as the 19th century. Both had lots of subtle reinforcement in all the places that could expect excessive wear. Where?
The nut-sockets were heavily reinforced with bone blocks. The front of the bridle (prod-binding) hole was reinforced with a slab of bone (or ivory) where the binding-cord lies against the inside surface. Both bows had heavy iron rivets running from bottom to top of stock an inch or so behind the prod-socket, to prevent splitting.
The Harnish bow showed a fair amount of compression of stock just behind the cranequin-pin and further compression of the bone-top where the cranequin would lie when spanning the bow.
Are all these things necessary for a 400 lb. bow? I think you could get away with a rather lighter bone reinforce around the nut-socket and a lighter rivet or bolt to reinforce the prod socket at that weight. For a thousand-pound bow (which the Harnish bow may have been... it was a mighty prod) you would probably want more reinforcing.
As for using a steel nut, I have seen horn/ivory nuts on Very Strong Bows, though the heaviest often have iron or steel pins driven down through the lugs of the nut, to prevent their shearing off. Actual steel or brass nuts are very rare indeed, at least till perhaps 17th century or later. Of course you would want a hardened steel sear-pin in the nut for the tickler (trigger) to bear against.
Does that answer your questions? Geezer

Geezer: Yes it does and more. Again Thank You Sir.

There is a Russian book on Crossbows that has a formula for rack and pinion mechanisms specifically aimed at calculating the ratios for cranequins. I'll Try to pull it up and post it here. Time to dig in my hard drive again.

Also there is a little useful program here: https://thearbalistguild.forumotion.com/t185-woodworking-for-engineers#1234 as well as a bit of into on the topic.