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Homemade lvl4 Crossbow

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#101 Forsaken angel24

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Posted 05 January 2008 - 10:27 PM

Just read the write up. Holy shit is that good stuff. I remember you were talking to me about this in the past but I didn't it would be that cool. You got the range, durability and accuracy. Now how about rate of fire. An over under barrel would help or maybe a homemade turret. Even if it was manual advancing.

Awesome write up.
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#102 CaptainSlug

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Posted 05 January 2008 - 10:31 PM

This size of hex bushing is much grippier than the the ones I'm use to so removing the CPVC barrels is actually kind of difficult. I'll have to try sanding down the ends to see if I can get a flip-around clip working.
For now I have the breech which works really well.
Posted Image
Eventually I would like to make a 6-barrel turret. But the options are limitless because I purposefully didn't design any specific barrel into the gun itself.
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#103 Cmdrmack

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Posted 05 January 2008 - 11:53 PM

That's a fantastic write-up. I kind of want to make one myself, as a backup for my X-bow. It's comforting to know that if anything ever happened to Sara I would be able to make something similar. I'm glad someone finally did this, it's been a long time coming.
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#104 penguin807

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Posted 06 January 2008 - 12:19 AM

Very nice write-up. I'm sure I'll eventually attempt this, but McMaster doesn't ship to Canada anymore, so it'll be quite a long time before I find all the parts necessary to make one of my own.
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#105 Jtcm

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Posted 06 January 2008 - 12:36 AM

Very nice write-up. I'm sure I'll eventually attempt this, but McMaster doesn't ship to Canada anymore, so it'll be quite a long time before I find all the parts necessary to make one of my own.

I know that people say that Mcmaster no longer ships to Canada but when i went looking through there help files I noticed it said that they will ground ship to most Canada. Was this section just not updated? Another quick question sorry does anyone know for sure whether or not Mcmaster will ship to American P.O. boxes?
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#106 flamebo388

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Posted 06 January 2008 - 01:50 AM

A question if I may. After examining the plans and pictures I wondering if you could shorten the plunger rod to 12" and still maintain the same functionality? It would appear there's at least an inch and a quarter of unnecessary length to the plunger rod. I ask only because it would allow one to purchase a square foot from mcmaster rather than the 2 square feet that is currently necessary. I may actually build one as the tools are all availible to me and I find myself with extra time.
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#107 CaptainSlug

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Posted 06 January 2008 - 01:53 AM

I'm fortunate enough to not care too much about the price of plastic sheets because most of what I use is scrap that I bought for a dollar per pound. Polycarbonate being my preferred material for most things because it can hold a thread and take a huge amount of abuse.

The plunger rod is made from 1/4" thickness polycarbonate and has to be 13-1/2" inches long in order for there to be enough material to allow you to bolt the priming handle onto it. If it were 12 inches long it wouldn't make it out the back of the rear frame piece.
The plunger rod is one part I would be willing to make for people if they are having difficulty. It's a very easy part to make using a table saw and a band saw, but not as easy to make cleanly with just a scroll saw.

OR you could order a 2-foot length of rectangular rod that has the right dimensions you want, then just cut it to length. The only thing usable that you can order is
8702K61 - Polyethylene (UHMW) Rectangular Bar 1/4" Thick, 1/2" Wide = $1.28 for 2 feet

Then order a smaller sheet of polycarbonate. UHMW Polyethylene is pretty durable stuff, but I'm not completely sure how well it will stack up against polycarbonate when it comes to progressive amounts of abuse over time. using it would be an interesting experiment and would shave $12 off the part list total.

Edited by CaptainSlug, 06 January 2008 - 02:02 AM.

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#108 Peter

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Posted 06 January 2008 - 12:03 PM

How difficult is the tapping and threading? Since I am guessing if you mess up threading the entire hole is screwed (no pun intended) unless a bigger size is used. So is it worth it to practice it a bit (no pun either) before performing it on the pieces that will eventually go on the gun. Luckily more than enough material will come with the order but I am hoping to be able to make 2 or 3. In going over the list will it be neccessary to order the appropriate multiples of the items that you put a specific quantity for, ergo things not in bulk. So I would need the following materials in multiples of the amount of guns to be made?


Black Nylon 6/6 Rod 1/2" (5 feet)
8538K23 - Nylon 6/6 Rod 1" Diameter
Polycarbonate Round Tube 1-1/2" OD, 1-3/8" ID, Clear
Zinc-Plated Brass Unthreaded Round Spacer 3/8" OD, 1/4" Length, #6 Screw Size
Aluminum Male-Female Threaded Hex Standoff 1/4" Hex, 1/4" Length, 6-32 Screw Size
Aluminum Female Threaded Hex Standoff 1/4" Hex, 3/8" Length, 6-32 Screw Size
Aluminum Female Threaded Hex Standoff 1/4" Hex, 3/4" Length, 6-32 Screw Size
Aluminum Female Threaded Hex Standoff 1/4" Hex, 1-1/2" Length, 6-32 Screw Size




Also, Is your breech merely a PETG tubing with the knob on it put inside the PVC? So when you slide it forward you can put the dart into the rear of the PETG? Which means I can substitute the PETG with Brass (and an appropriate PVC size)

Next, Where did you find full sheet labels? I looked at all of my office stores but to no avail, later this week I will check kinkos though.





Thanks.

Edited by Peter, 06 January 2008 - 12:06 PM.

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#109 CaptainSlug

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Posted 06 January 2008 - 01:12 PM

Concept plan for a manual-advance rear-loading 8 barrel turret.
Posted Image
I should be able to make one of these before Friday. Assuming I can make enough darts first.

1. How difficult is the tapping and threading?

2. So I would need the following materials in multiples of the amount of guns to be made?

3. Also, Is your breech merely a PETG tubing with the knob on it put inside the PVC? So when you slide it forward you can put the dart into the rear of the PETG? Which means I can substitute the PETG with Brass (and an appropriate PVC size)

4. Next, Where did you find full sheet labels?

1. All of the plastics chosen to make this gun are very easy to tap. You can even tap polycarbonate using a poly drill with little effort. Just make sure to keep the tapping bit from getting too hot, and clean the shavings off of it after each hole you tap.

2. Here's a list of materials you will need to order more of and why.
Provides some excess, but not enough to make more guns.

8541K18 - Black Nylon 6/6 Rod 1/2" Diameter = $1.02 per foot (5 feet) = $5.10 Each


For the items below multiply amount by the number of +bows you are trying to make.

8585K43 - Polycarbonate Round Tube 1-1/2" OD, 1-3/8" ID, Clear = $3.48 for one Foot

4880K314 - Std-Wall (Schedule 40) White PVC Pipe Fitting 1" X 1/2" Sz, Pipe End Male X Socket Fem, Hex Bushing = $0.74 Each

90309A154 - Zinc-Plated Brass Unthreaded Round Spacer 3/8" OD, 1/4" Length, #6 Screw Size = $0.57 Each (2)
93505A440 - Aluminum Male-Female Threaded Hex Standoff 1/4" Hex, 1/4" Length, 6-32 Screw Size = $0.49 Each (2)
91780A125 - Aluminum Female Threaded Hex Standoff 1/4" Hex, 3/8" Length, 6-32 Screw Size = $0.34 Each (4)
91780A131 - Aluminum Female Threaded Hex Standoff 1/4" Hex, 3/4" Length, 6-32 Screw Size = $0.44 Each (3)
91780A337 - Aluminum Female Threaded Hex Standoff 1/4" Hex, 1-1/2" Length, 6-32 Screw Size = $0.78 Each (2)
You do not need more of the 1" diameter rod because it is only cut to 3/8" lengths to make the core of the plunger rod. The pack of 100 3/8" length screws will give you just enough to make three guns (the gun uses around 33 of that length of screw).

3. I had to bore out the inside diameter of the PVC pipe using a machine lathe to get the PETG to slide and seal inside of it. I then milled the notch using a manual knee mill.
I solvent-welded a tab onto the PETG to make sure the barrel doesn't slide forward when the gun is fired.
I don't recommend trying to make this kind of breech if you do not have access to a lathe and some practice using it.

4. Office Depot, Staples, and sometime Target carry them near the other kinds of label paper. like the return address or mailing label ones that are pre-cut to size. They're kind of pricey at around $35 for 100 sheets.

Edited by CaptainSlug, 06 January 2008 - 02:13 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#110 nerfer34

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Posted 06 January 2008 - 03:32 PM

That would be the most dominate nerf gun in the history of nerf.

8 shots at 120'. And you can probably get those 8 shots off in 10-12 seconds....

That's just great work.
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#111 General Cole

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Posted 06 January 2008 - 04:22 PM

Now it needs a shotgun pump. I think I can get these parts made at the rapid prototyper at the college here. Depending on the cost, I may be able to sell some parts. I also am not sure about the durability. If anyone has a Desktop Factory, you may want to contact them.
We should stop calling out/making fun of/pissing GC off. He's actually contributed and is available for trade. He's a better than average member no doubt. Got your back Cole.
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#112 CaptainSlug

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Posted 06 January 2008 - 08:40 PM

8 shots at 120'. And you can probably get those 8 shots off in 10-12 seconds....

No, probably not that fast. It will probably be more like 45 seconds

1. Now it needs a shotgun pump.
2. I think I can get these parts made at the rapid prototyper at the college here. Depending on the cost, I may be able to sell some parts. I also am not sure about the durability. If anyone has a Desktop Factory, you may want to contact them.

1. I know of one way to add one, but I don't think it would make it any easier to prime such a powerful spring unless my arm were as big as FA24s.

2. That's a generous offer, but current 3D printers print parts in either urethane with a binder, ABS, or a light cured polyester or other resin medium. None of those materials are strong enough to make most of the parts for this gun. They're great for demonstrational models, but for actual working parts all but the ABS 3D printers are not useful.
And to make the parts out of ABS I would have to design them with that material in mind.

Edited by CaptainSlug, 06 January 2008 - 08:44 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#113 VACC

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Posted 06 January 2008 - 09:33 PM

Just out of curiosity Cap'n, what are you going to use to create a tight seal between the 1/2" bushing and the turreted barrels? The mechanism in the doom sayer has a air chamber that gets snugged up to each breeched barrel, but all the shots I've seen of the +bow would indicate that your chamber is backed off a bit from the opening in the bushing to allow for inserted barrels. Now, with 8 shots you could easily afford to lose a little range (especially since you can just pull the plunger back an exta tick to offset it) but knowing your work, I doubt you'd settle for such a compromise.

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#114 CaptainSlug

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Posted 06 January 2008 - 09:43 PM

The back face of the turret is spring-pressed against the mounting plate that is bolted to the barrel stub that locks into the hex bushing. I should get a decent seal between the plates, but if not I can lathe the end of the barrel stub and add an o-ring to it.

Edited by CaptainSlug, 06 January 2008 - 09:44 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#115 General Cole

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Posted 06 January 2008 - 09:52 PM

http://www.desktopfactory.com/

Thats what I was thinking. Their stuff looks to be pretty durable. And its made out of high density plastic, and you can insert an even higher density pellet to make the parts stronger.
We should stop calling out/making fun of/pissing GC off. He's actually contributed and is available for trade. He's a better than average member no doubt. Got your back Cole.
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#116 CaptainSlug

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Posted 06 January 2008 - 09:56 PM

Yes I know about their products. And like I said previously it's not really at all useful for making parts for this gun since only a few of the parts fit in the 5x5x5 inch space the printer has and could be made from that type of plastic without breaking after a months worth of use. At most you could make the catch plate, trigger, and priming handle. But everything else would have to be made from much stronger plastics.

I research manufacturing options for both work and fun. I'm weird like that. Water-jet and laser cutting services are really the only feasible ways of making these parts in bulk. But the cost for services with those tools are much higher than I want to pay.

I don't need anymore manufacturing suggestions.

Unless you
1. have a relative that is willing to give me a significantly reduced rate on that type of service
2. have a laser or water-jet cutting table at your disposal and are willing to bend to my whims for a share in the profits making these guns
3. for some strange reason have $13,000 dollars you don't have anything to do with and would like to just give it to me so I can buy a laser cutting table

then I probably don't near to hear about it at this time. Thank you.

Edited by CaptainSlug, 06 January 2008 - 10:03 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#117 six-five-two

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Posted 07 January 2008 - 12:48 AM

That tutorial is... amazing. Good work!

Can't you find an already used laser cutter?
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#118 CaptainSlug

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Posted 07 January 2008 - 04:03 AM

Can't you find an already used laser cutter?

Used ones that do go up for sale are the gigantic 9x6 foot models from the 80s and will sell for the same price as newer smaller ones.
It's not an item with a high turnaround rate.
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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#119 angrscottishkid

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Posted 07 January 2008 - 03:38 PM

Sorry if this has been asked before, but about how much do they cost to make from scratch?
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#120 CaptainSlug

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Posted 07 January 2008 - 03:41 PM

Sorry if this has been asked before, but about how much do they cost to make from scratch?

Initial supply cost if you're buying all the materials is around $80. But if you make one it involves $20-$30 of parts and supplies and you end up with $45 worth of excess. There's no way to buy exactly how much you need.
I have lots of scrap plastic, so I can't calculate precisely how much each one costs me to make. It's probably around $20.

Edited by CaptainSlug, 07 January 2008 - 03:53 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#121 precisionnerfer

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Posted 07 January 2008 - 04:09 PM

So let me get a few things straight:

A. These guns and ideas will and do and can rock the house.
B. None of us can make them without paying a freakin lot for tools, materials, and parts.
C. The only person on the Haven who can and will make them is Sluggy.
D. He is the only person to buy them from.
E. Sluggy can make a small fortune off of this?

(F.) I got my foregrip today, it's sweet, TY.
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#122 CaptainSlug

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Posted 07 January 2008 - 04:25 PM

So let me get a few things straight:

A. These guns and ideas will and do and can rock the house.
B. None of us can make them without paying a freakin lot for tools, materials, and parts.
C. The only person on the Haven who can and will make them is Sluggy.
D. He is the only person to buy them from.
E. Sluggy can make a small fortune off of this?

A. Pretty much
B. The only expensive tool I own is a contractor grade table saw, which I didn't really make heavy of to make this gun. At bare minimum you will need a power drill ($30), a scroll saw ($100), and a tapping bit ($6).
C. There are at least 10 other members I am aware of that have the tools needed to make these on their own. There are probably others I am not aware of.
D. Debatable. If you have a friend who has the right tools and a weekend in which they would be willing to help you, I'm all for you buying them dinner or bribing them in some other manner to help you make your own.
E. If by fortune you mean I would be compensated for the 10 hours (one whole waking day of effort) it would take to make one, then maybe so. If I had a more efficient way of making these I could reduce the price significantly. As it stands now, if I do make more of these with the intent to sell them the starting price will be $120 each. That's $20 for supplies and $10/hour for labor.

And speaking of the foregrip kits, my time is compensated when I make those as well. I wouldn't make and sell them if I had to do so at a loss.

Edited by CaptainSlug, 07 January 2008 - 04:29 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#123 precisionnerfer

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Posted 07 January 2008 - 04:36 PM

Oh, missed that it took 10 hours. Heheh....
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#124 General Cole

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Posted 07 January 2008 - 09:07 PM

Me and Trojan Nerf will be making them when we finish our first batch for ourselves. We will have 3 guys working in assembly line fashion at a machine shop, so, as soon as supplies are bought, we will be fine, I can estimate 80 dollars if I did the math right.
We should stop calling out/making fun of/pissing GC off. He's actually contributed and is available for trade. He's a better than average member no doubt. Got your back Cole.
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#125 n-strike

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Posted 08 January 2008 - 12:12 AM

Me and Trojan Nerf will be making them when we finish our first batch for ourselves. We will have 3 guys working in assembly line fashion at a machine shop, so, as soon as supplies are bought, we will be fine, I can estimate 80 dollars if I did the math right.

But of course, yours can't be as good as Slug's. And what would be $80?
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