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Plusbow prototype


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Poll: Plusbow prototype (55 member(s) have cast votes)

Do you like this plusbow?

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#1 kbk652

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Posted 13 February 2014 - 09:21 PM

Hey guys I have been working on this for about a week now, and I want some feedback, and some suggestions and thoughts.
First I want to give thanks where it is due, roboman was awesome and gave me some models and it was a great starting point.

Specs
All the red is 1/8 inch aluminum and the black except the priming bars is a plastic
Has 7" of draw on a full [k26]
Uses a rainbow catch
A 1.5 OD plunger tube and 1.375 ID
Need to put some small detail works and the catch.

Before I start machining anything I am looking to print the handle if anyone can help me out let me know the dimensions are 1.25" X 3" X 12"

If you are interested in one PM me and I will gladly work something out with you

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Edited by kbk652, 17 February 2014 - 01:44 PM.

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#2 Bchamp22795

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Posted 13 February 2014 - 10:59 PM

I'm not a big fan of the handle, and with so many holes, it looks "too busy" in my opinion, and loses elegance.

Edit: By not liking the handle, I meant I am not sure it looks very comfortable. I'm no expert by any means, but it could be more ergonomic. I don't like the holes in the priming bars, side plates, and stock....pretty much everywhere there are holes.

Edited by Bchamp22795, 14 February 2014 - 01:55 PM.

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#3 kbk652

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Posted 13 February 2014 - 11:41 PM

I'm not a big fan of the handle, and with so many holes, it looks "too busy" in my opinion, and loses elegance.



Just curious of what part you are referring too? the handle the part where your hand goes only has the two holes are you referring to the priming sides or the holes in the back near the stock area?
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#4 archangel24

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Posted 14 February 2014 - 01:00 AM

I have to agree with Bchamp on the plethora of holes. I has circular holes, rectangular holes, and a doubled rectangle hole to form a square pattern. There is too much going on in the design. I get that you are cutting down on weight but that is just too much. Stick to one hole design. The beauty of roboman's Al plus/pumpbows is that the side plates were very uniform in the design and weren't extravagant or gaudy. This looks like, sorry to say it(not trying to insult your intelligence), a 10 year old child's crack pipe dream of a homemade blaster. You have a great foundation, you just need to streamline, cut down, and increase uniformity in the design.

For the handle, I would go back and possibly change it abit. Only so many people feel comfortable with squared handles. They just aren't for everyone. A design closer to roboman's for 3D printed handles would probably be a bit better for a more ergonomic and universal blaster. I get that this blaster is for you, well intended primarily for you but when contributing to the community, you want a design that would be better for the general amount of the audience that would be viewing it and interested in. Aditionally, in the long run, a more ergonomic grip is better for extended use because it puts the hand in a more comfortable, less stressful position, allowing the user to be able to use the blaster/gun for longer durations of time. When looking at firearms(gasp), they tend to follow those same criteria.

The main part of the whole blaster design that bothers me is the support bars from the sideplates to the stock, as well as the bars for the priming handles. The holes would allow for it to be lighter weight but also decrease strength of the material when putting a direct but inconsistently changing force on it. In a perfect world where people don't torque things around the design would be fine but you run the risk of having to replace those parts if torqued as they would be able to give more. This is due to taking out so much material that it puts unnecessary weak points/fail points in the bars which are meant to be able to take a significant amount of load. But as most people know, especially those who use stocks (look at recon stocks) and pump action priming methods, it is very difficult to keep all the stress in one single direction(straight back for priming and straight forward when shouldering a stock). I'm not trying to reticule you on the design but this is a major flaw for functionality and stability and I would hate for you to have to find it out first hand after the fact.
Edit: After looking at the plastic portion of the stock torquing is not as much of a problem as getting it hit would be, very easy to do.

Something that would be nice to see would be a cheek rest somewhere in the stock, as opposed to resting your cheek on the Al stock support bar. Easy way to get face diddled if you don't have it smoothed out well.

Edited by archangel24, 14 February 2014 - 01:03 AM.

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#5 kbk652

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Posted 14 February 2014 - 08:05 AM

I see where you are coming from with the amount of cuts in the sides, I attach the plungertube in the back so some of the holes are needed.

The handle is not as square as shown it actually has quite a tapered edge, but this is the part I am trying to get printed so I can test out how it feels before I move to the real material.

The aluminum sides they are all made from 1/8" aluminum and I do not see any issues with the stresses coming but if someone wanted me to not drill the holes lol well that's simple enough.

I like the idea of something to rest on, I may change the back hole pattern to say like 1/8 holes so that whatever I use back there is adjustable for people and not just one huge piece of say plastic.

Thanks for the suggestions

EDIT: I made a quick model of a more uniform side plate.
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Edited by kbk652, 14 February 2014 - 10:25 AM.

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#6 roboman

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Posted 14 February 2014 - 10:45 AM

I'm not really sure why you put sideplates on this thing, as they don't appear to be doing anything at all. The whole point of using them is to bear the load caused by the plunger head impacting the bushing, since a thinwall polycarbonate tube can't do that very well. It's probably a good thing that those plates aren't under any significant load, though, because you took out an awful lot of material from them, and I'm not inclined to believe that they'd hold up well over time. I'm glad you added the internal radii to the design you posted most recently.
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#7 Meaker VI

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Posted 14 February 2014 - 11:22 AM

EDIT: I made a quick model of a more uniform side plate.
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That is more uniform stylistically, but you should probably keep the outline of the piece intact.

Don't cuts like those add cost to the piece anyway? Do some kind of cool design or something if you're going to pay extra to remove material (and also strength) from your blaster.
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#8 kbk652

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Posted 14 February 2014 - 05:48 PM

I do not have to pay to use the machine shop for my school.
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#9 Just582

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Posted 15 February 2014 - 10:57 AM

Like everybody else, I'm not a fan of the holes, especially in the priming slide thingy. The pump action grip looks really small, and the main handle looks odd. I am absolutely loving the stock, the bottom half and back looks almost like a real nerf crossbow. If you have a nerf crossbow, you should model your plusbow to look like and have the comfort of a real crossbow.

Edited by Just582, 15 February 2014 - 10:58 AM.

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#10 kbk652

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Posted 15 February 2014 - 09:37 PM

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I made so quick changes based on some feedback, just a quick model.
I added in a cheek rest that is adjustable with the back for however people want.
I added in round edges on the handle, I may go in with like detailing for like your fingers but havent gotten to it yet. I may change the red piece to make the grip feel better.
I made the front priming grip alittle bigger and more of a cup for your hand.
I feel like a good offering would be on the priming bars, I will engrave something, like a username, name stuff like that.

Let me know what you guys think of this?
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#11 roboman

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Posted 15 February 2014 - 10:09 PM

The design just doesn't flow well. The lines aren't very clean, and you've got a bunch of different angles that clash with each other when they're stacked, specifically near the grip. Don't let the triangular pockets cut into the outline of the sideplates unless you absolutely have to. I did so on mine to provide clearance for the pump grip.

How do you plan on machining these, and what's your price point?
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#12 kbk652

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Posted 15 February 2014 - 10:19 PM

The original one priced to be about 125 plus shipping, great part about my school is that anyone who has passed training on the machines can machine
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#13 roboman

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Posted 15 February 2014 - 10:29 PM

I see. How long do you expect each blaster to take to build, and where are you getting your materials from? I'm asking mostly because I'm concerned that you haven't completely thought this through. Each of my pumpbows needed about 2 hours of CNC mill time, ~$30 in materials and parts, and many more hours of post-processing (mostly cross-drilling and wire brushing), manual lathe work, and assembly. That's why I'm not making any more after I finish the 16 that were commissioned. In my case, they paid for a trip to Apoc, a 3D printer, and a semester's worth of gas, but I still didn't even come close to making a reasonable hourly wage for the work I did.

And yes, I understand that. What kind of equipment is it (make, model, etc.)?
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#14 kbk652

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Posted 15 February 2014 - 10:40 PM

I dont remember the exact model numbers but hass mills and lathes most of my material is coming through Mcmaster, once I have made one, and wrote all the code I think it will be about 6 to 8 hours per blaster. But way before I start selling I was going to make atleast two to see how long it takes, if i need changes, all of that, which is why I want to get some handles made to see if i should change them before I make them out of plastic.
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#15 roboman

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Posted 15 February 2014 - 11:13 PM

Interesting. My high school had two TM-1s and two TL-1s, though I ran all of my pumpbows on a 1989 Bridgeport Interact 412X with a Fanuc O-Mate control (which I might be buying from the community college within the next year or so at scrap metal prices).

Do yourself a favor and don't buy metal from McMaster. At least use Onlinemetals.com, if not a local supplier. I get my aluminum for about $2/lb after all of the discounts they give me, both because I'm a student and because I got to know them really well over the last year and a half. A few years ago, before I knew about my current supplier or OnlineMetals, I quoted the material cost for an aluminum plusbow on McMaster, and it came out to a little over $100 worth of stuff. 1/8" aluminum sheet is currently about $25/square foot on McMaster, which is absolutely ridiculous. It's about $14/sq ft. on OnlineMetals, and it was $11 for a custom cut sheet that fit 4 sideplates with enough room for my fixturing on the sides at my supplier (somewhere around 14" x 12").

By the way, assuming a $50 material cost per blaster, you're looking at $7.50-$12.50 per hour, which really isn't that much when you consider how much work you're doing.

I really hope you know how to use both that mill and MasterCAM (or whatever CAM package your school uses) very well. It is not a small undertaking to optimize that setup for machining. You're going to need a fixture plate of some sort (or you'll have to pull the vises off, put a spoil plate underneath your sheet, and use strap clamps).
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#16 kbk652

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Posted 15 February 2014 - 11:42 PM

Lucky you with that bridge port, I was able to quote 6061 for the sides at like 10 plus shipping I didn't get the shipping costs because it was mcmaster. How good is Onlinemetals? like with shipping and custom cuts?

Like I said I haven't built one yet so if people were interested in it now I would quote at that price not knowing how long I would be in the shop for. after building some I might change the cost depending on how much time and work actually goes into one. On the design part I really just wanted to try something different I don't want to copy someone else's hard work and sell it.

So the price 125 will be for now and once I make them I may have to raise the price.

What aluminum were you using? Also the machine is a haas sminimill, and the S-10 lathe, I believe we have the TM-1 in the other shop.
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#17 roboman

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Posted 16 February 2014 - 12:44 AM

That bridgeport isn't nearly as nice as any of the Haas stuff, but it'll be nice to have a VMC in my garage when I'm home for vacations.

OnlineMetals is fantastic, and their prices are around half of what McMaster charges. Shipping is pretty reasonable, and their custom cuts are never undersized. They were my main supplier prior to Max Industries, the place I use now. Unfortunately, Max doesn't ship, so I have to have my dad pick it up and mail it to me in a flat rate box, though that's still cheaper for me than any other supplier in existence.

Good luck with that, though. You'll be standing in front of that machine for a long time. Those Mini Mills are pretty sweet, though, and ST-10s are production turning centers. There's one in one of the shops at RPI, along with a Super VF-2, TM-1, TL-1, and ST-10 (and a bunch of other Haas stuff all over campus, including a VF-5 in the physics building for no apparent reason - it's big enough to fit a small sedan on the table). I use 6061-T651/T6511, which is less gummy than normal T6.
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#18 kbk652

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Posted 16 February 2014 - 12:54 AM

Still rocking just my dremel and drill so a bridgeport would be amazing but good luck moving that thing. Do you happen to have a 3d model of the grip for your plusbows?
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#19 roboman

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Posted 16 February 2014 - 01:03 AM

Yeah, it's a 4800 lb CNC mill, and I'm also going to have to have 220V 3 phase run to the other side of my house from the breaker box, so it's gonna be interesting.

I do, it should be in that dropbox folder. Here's the link again if you don't have it. I think it's called "grip.sldprt" or something along those lines.
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#20 kbk652

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Posted 16 February 2014 - 01:06 AM

Do you have any printed?
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#21 roboman

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Posted 16 February 2014 - 01:09 AM

Yeah, I've got a few that aren't on anything right now. If you want one, PM me or something and we'll work it out there.

Edited by roboman, 16 February 2014 - 01:10 AM.

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#22 Darth Freyr

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Posted 16 February 2014 - 01:35 PM

Looking at this design as a whole, it seems pretty excessive for what seems to be a first time (Nerf) builder. Personally, I would remove all the decorative machining, at least until you are sure the design works. There are also quite a few other things that stuck out as concerning to me.

The trigger looks to have quite a few possible issues. The first one being the question of reach. I can't be sure just from looking, but it seems like you would really have to stretch your trigger finger in order to actually pull on the trigger. In my experience, the trigger shouldn't really stick out a whole lot beyond the line of the handle, as you do want your index finger to get a decent wrap around it. You can't pull a trigger if you're juts scraping it with the pad of your finger.

Still on the trigger, it also looks like it would pinch your middle finger when you pull it. Again, I can't be sure without seeing how far it swings, but I bet your hand is going to be migrating up that handle if you start to do anything like run around with the blaster.

This may be more questionable, but the angle of the front face of the trigger looks uncomfortable. Currently, it looks like it is angled backward pretty sharply. As you pull on the trigger, that's going to push downward on your index finger. And the angle will only get worse as the trigger rotates further backward. Generally, I like to have the front curve of the trigger to start bending forward again, at least until the point that the bottom-most as at least vertical when the trigger is fully pulled.

I also see a lot of potential problems with your pump-action system. Starting from the front, you always have to be careful when applying offset forces to a mechanism, such as having the pump grip significantly below the plunger rod. Pulling on the handle is going to generate significant torque that has to be canceled out somewhere. You also have to make sure your connection can handle that torque in addition to the linear forces. Additionally, I cant see any sort of guide or tracks for the pump. What happens if pull slightly downward on the pump? Would it just come off of the blaster completely? Moving backward, I would also remove the aforementioned holes in the rods/bars there.

The whole back end of the pump system also looks extremely dodgy to me. The images do not show it very well, but it looks like you just have a couple of screws through the bars, sticking inwards. The first problem is another of torques: what would stop the bars from just bending there? Or the whole bar just bowing outward? You also have to make sure that the screws are going to stay fairly centered vertically on that plate at the back of your plunger rod, or else you're also going to be torquing it as well. A better solution might be to have a standoff above and below the plunger rod, connected to both sides of the pump. That way, the potential bowing of the pump bars is greatly reduced and the forces on the plunger rod will stay vertically balanced.

There also appear to be a decent number of structural problems with the design as a whole. As roboman mentioned, your side plates don't reach the front of the plunger tube. This means that the bushing at the front of the plunger tube would be supported only by the thin walls of the plunger tube. This would probably be okay if you use aluminum for the tube, but it would be a very bad idea with polycarbonate. The way that the plunger tube is currently mount also looks like any motion on a barrel or hopper assembly, or any unintentional forces on them, are only supported by the mounting in the very back. That could potentially lead to a large stack of broken or cracked plunger tubes. I would also suggest some sort of horizontal support at the top of the side plates, like sticking a standoff between the holes that connect the top stock bars to the side plates.

I think you might also have some problems with your stock, particularly with how it connects with the rest of the blaster. Right now, all the support for the bottom of the stock comes from those two screws at the bottom of the handle. Transferring that force into the main frame of the blaster is going to come from shear forces. Those pieces on the handle on not very wide, and not very thick. Personally, I wouldn't be that comfortable stressing them like that. I think a lot of this problem could be averted by putting another screw between the two parts near the top of the handle.

There are a few other assorted things as well. It looks like the holes in the top bars on the stock don't line up. This isn't a problem on its own, but it might indicate other inconsistencies in the geometry. 7" of draw on a [k26] is probably overkill, I think you'd be better off with something closer to 6"-6.5". You might also want to check the unprimed spring length in the blaster. Springs may shorten up a bit from their new length after some use, and having a spring rattling around inside a blaster is annoying. Also, you might want to be careful with that sort of catch notch on your plunger rod. It has definitely been done successfully, but it usually means a thinner catch face, so you might want to be sure that you don't round over the edge too much, on either the plunger rod or the catch plate.

I know that this response might seem extremely critical, but I just wanted to point out some things I've learned from my experiences so they don't surprise you later. It's also how I think I communicate most clearly.
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#23 spencerak

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Posted 16 February 2014 - 06:53 PM

Specs
All the red is 1/8 inch aluminum and the black except the priming bars is a plastic
Has 7" of draw on a full [k26]
Uses a rainbow catch
A 1.5 OD plunger tube and 1.375 ID


I'm not sure what the point of having side plates is doing for the blaster, to me it simply looks like you are adding work and material cost to something that has already been proven to work perfectly fine. Your end product is basically a rainbow pump with 5lbs of aluminum stuck on the side. Sure it looks kinda nice after you made only one pattern on the side plates but I still don't know why you have side plates to begin with. Also in you side plates dont have any of the geometry open to the outside because it is aesthetically unappealing. I'm not sure if you understand that side plates are meant for structural stability of a blaster with a thin plunger tube as well as a means to hold the catch both of which have been completely contradicted by your build. I just think that they are a useless addition raising the material cost and machine time of something that does not need them for function or structural integrity.
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#24 quertyman

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Posted 20 February 2014 - 09:27 PM

To be honest with you. I think you would be better off if you took some time to build a few and revise and perfect your design before you try to start selling them off to people. The reason roboman has been able to get so much attention is because he has the reputation of making some amazing things. Just because you have the tools doesn't mean you can pull off crazy designs. I would start by proving that you can make some quality things with those big expensive machines that you have access to. Just some friendly advise before you get stuck with 20 people bugging you about commissions and out 125$.

EDIT Also, 9000 people aren't a fan of your design and 9001 people think polls are dumb. :P

Edited by quertyman, 20 February 2014 - 09:28 PM.

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#25 kbk652

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Posted 20 February 2014 - 09:34 PM

To be honest with you. I think you would be better off if you took some time to build a few and revise and perfect your design before you try to start selling them off to people. The reason roboman has been able to get so much attention is because he has the reputation of making some amazing things. Just because you have the tools doesn't mean you can pull off crazy designs. I would start by proving that you can make some quality things with those big expensive machines that you have access to. Just some friendly advise before you get stuck with 20 people bugging you about commissions and out 125$.

EDIT Also, 9000 people aren't a fan of your design and 9001 people think polls are dumb. :P

In a few weeks me and my friend are going to go into the shop and make a few different ones. This was designed as to see what people thought I have already been changing around the design. I would make a different one with a finished product way before I sold any.
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