Plans and materials for my first build

First topic message reminder :

If this is in the wrong spot or in anyway not in line with forum policies, my apologies!

So I am an absolute beginner crossbow builder, but I have some wood working and bowyering experience as well as decently fitted out little wood shop in my basement. I think this is gorgeous and is what I'd like to try to build:



Am I out of my gourd? I think I'm at the reach of my abilities here... The parts where I have real concerns are the trigger mechanism (more on that in minute) and mounting the prod.

I am starting to gather materials and draw out plans. So far I have red oak for the stock and some steel banding to replicate the mounting plate as seen in the picture above. 

I am going to keep this fairly low draw weight at between 80 and 100 lbs and was wondering if delrin would be strong enough to make a nut from. Never having worked with it before, I'm not sure of its limitations.

The trigger/cam would be delrin, the lever steel, the nut delrin. All critiques are welcomed on this as I'm really not sure what I'm doing, lol.

The prod I'm considering would either be a manufactured one like on the crossbow pictured or using the tips of cross country skis to make my own. I'm not 100% how the prod is held in place in the photo, or in the series of photos this pic is taken from. Anyone have any guesses? Thanks in advance for any and all help!

Model of the proposed trigger to make sure that I got everything measured right and that it actually works. Had to make a couple of adjustments to some things. Still need to figure out a safety - if anyone has any suggestions, I'm all ears! Also, thank God for scroll saws.

Bamboo for the table is cut, just needs to be planed down to the thickness I need.

Shaping the grip. I thinned it down on the table saw to be more comfortable in my hand. We'll see of the Luger handle style lasts... it's going to be hard to maintain it's sharper edges through the refining and sanding process. So far the red oak has been great to work with.

Also cut out the location for the prod. Pretty good couple of hours this afternoon. Progress!

The new metal-cutting band saw blade arrived today and was quickly put in to use. What had looked to me to be the most daunting task of this build, cutting out the trigger and actuator was a much easier process than I could have thought. Well, so far anyway. The trigger and actuator are 1/4" thick bar stock and the side plates are 1/8". They're just rough cut at the moment, final shaping to be filed and Dremeled over the weekend.

Trigger and actuator with the casing. Screws I got in this pic are too short, had to run out and get longer ones and will likely have to trim them flush when this part's complete. Going to use the pins shown as axles for the trigger and actuator, the roller nut will be held in place with a Chicago bolt through the casing, side of the xbow and an aluminum plate on the side of the stock.

Still have yet to figure out a good, clean safety. I've seen a lot about where to place them; at the trigger vs. the sear, etc. just not how to actually MAKE one.

Anyhow, it's coming along!

Looking good!

Are you planning on hardening the trigger sears? Are they regular mild steel?

Andy. wrote:Looking good!

Are you planning on hardening the trigger sears? Are they regular mild steel?

Hi Andy - thanks! I decided to go with an aluminum mechanism with steel pins and steel machine screws. The trigger is 1/4" thick and has a shear strength of 9000lbs psi. With the prod only being 150lbs at an 11 1/2" draw I think I'm safe. I will definitely be testing the mechanism thoroughly first though!

The hardening of the pieces has nothing to do with how strong they are, only how smooth and easy they work together, known as the release. Hard facing softer metals can be done a couple of easy ways. I like what I've seen of your trigger so far.

Are you planning to make a hard face for your string catch?

were you planning on making a hard face for your string catch?

Hey - Could someone tell me how much tension is supposed to be on the nut when it's at rest? Should it just spin freely, be a little loose, or should it be tight enough to hold position without rotating?

Thanks!

c sitas wrote:The hardening of the pieces has nothing to do with how strong they are, only how smooth and easy they work together, known as the release. Hard facing softer metals can be done a couple of easy ways. I like what I've seen of your trigger so far.

I'm thinking maybe I misunderstood the previous question of hardening. I was thinking of a harder metal like steel vs. aluminum. How can I hard-face aluminum, never heard of it before?

Nice design, but imo, alli will likely gall or fail completely at the sear points. Way too soft

Chillihook , sorry I haven't been around for awhile. Maybe you slightly misuderstand  me  about hard facing. I've sucessfully used this on a lot of my homemade crossbow locks.  Starting with a delrin string claw, I hard face that in two places. Next using a lum. , I'll epoxy piesces of old hacksaw blades to a face that I want hard. Carefully grind to shape. When held by your fingers , you don't have to worry about harming temper. I always use JB weld , never had one let go in over 5 years  of monkey work. This method really makes a difference in the pressure used to move a surface. such as a trigger. I forgot to mention that I like to polish one side of the blade, while scratching up the other side for a good for a good bond.

c sitas wrote: epoxy piesces of old hacksaw blades to a face that I want hard. Carefully grind to shape. When held by your fingers , you don't have to worry about harming temper. I always use JB weld 

Great tip! thanks for sharing

Things have been a bit slow lately as I've had to make some adjustments to the trigger mechanism. I decided to go with stainless steel parts for the whole thing. Going to take a little bit of time to get them made up and done (had to farm them out, just no tools to work on steel like that), but should have them by mid-April. Also had the prod mount, stirrup and stirrup mount made out of stainless too.

More to come!

These finally arrived yesterday. Shouldn't complain, took less than a week to get them. Feels like I cheated going this route, just no real way to work with steel at my house. Laser cut stainless steel. Still need to countersink and tap the side plates and bend the pieces of the stirrup. The only part left to have made is a steel nut. That might take awhile though.

:::A little bit of grossness warning:::



Well, a bit of carelessness and the shop gods exacted a blood sacrifice. Could've been worse, but bet it stings tomorrow.

Man, get some duct tape on that thing. I tape as soon as possible then worry about cleaning it. Found over the years they heal way faster than stitches. Better to be more careful to start with.also on the subject of your steel nut. Maybe you could consider a nut made of delrin with metal inserts. I use these all the  time when making triggers . Gezzer on this forum showed how to do this . Works perfect and have never had a failure. They are way better on string wear also. also  , you had mentioned a saftey. The best safety is always on the sear. in your wooden mock up , if you look directly above the end of the  sear and straight up from the trigger, vision a lever at that position that when moved , it would exstend down and block the upward movement of the sear. The state where I live mandates a safety for hunting crossbows period.

Trigger assembly about 75% complete. Tapped all the holes that needed it, had to ream some of the holes prior to countersinking so that the machine screw wasn't threading the front of the plate. Nylon washers and shims to space. Need to deburr the front stainless pieces and mount them as well as "hardening off" the nut I have with a piece of old hacksaw blade. Next I think will be mounting the prod locks and then routering out the cavity for the trigger mechanism.

Stirrup assembly. Still needs cleaning up. Not exactly how I wanted it to come out, but I'll take it. Bending stainless steel is no joke!

Looking good!

looking great,have you thought about some spacer tubes over the screws to keep the lock sides dead square?

tghsmith wrote:looking great,have you thought about some spacer tubes over the screws to keep the lock sides dead square?

I hadn't, but that's a great idea - thanks!

Kind of a 'dry fit' of the prod mount/ stirrup assembly. Looks okay right? Figure I'm about 50% of the way there...