M249 advice

SiliconeSword said:

Not fusion360, but there's this new thing called Onshape that I'm learning right now, apparently it's better than 360 some say.
I don't have experience with either, but my school switched to this and the teacher likes it more for various reasons.
The cost is that your designs are public, unless you pay for it.

Click to expand...

I remember this. It was given as an alternative to Fusion/Solidworks for our coursework.
I didn't like it that much, mostly because it lagged a lot, since it was in browser, and at the time my internet was kind of broken. This is something to bear in mind. I mostly used fusion, however, the free version is kind of annoying, what with the limited number of models you can make. It doesn't really affect anything, but it is slightly fiddly.

The big problem with Onshape is that (as you said but also):

1. All your designs are public, unless you pay (as you said).
2. If you want to sell your design, you are not allowed unless you pay.
3. However, if somebody downloads your design, they can commercialise it. Basically, everybody but you can sell your design.
4. It is only CAD, Fusion also has CAE capability.
5. A paid plan is $1500 minimum. Cheapest fusion plan is €320 ish.

On a seperate note, if you are ex, reserve or active military, in the US and Canada, I'm pretty sure you can get Solidworks Student for $20 per year.

If you are skilled enough, you can go oonga boonga caveman brain and cast it in silica sand.

That depends on what you want.
If you want something free for 3d printing and CNC, it's probably going to be Fusion 360.
If you want to scuplt models for WH40K or whatever, its going to be ZBrush (paid).
If you don't mind paying it'll be Autodesk 3ds Max or Solidworks (student subscriptions for SolidWorks are available).
If you want to Animate, it will be Maya, Houdini, Cinema 4d or Blender (Maya is by far the better choice).

Personally, I use fusion, however, I can't really testify on how good it is, because I'm trash at modelling.
It's like with a tennis player. Give a poor tennis player a good racket or a bad racket and he can't tell the difference. You need to be good at something to tell if the tools are good.

The big detractor to things like Onshape and Fusion, is also their biggest advantage: they are cloud based. On the one hand, you can access your files from anywhere. On the other hand, Autodesk (or whoever runs onshape) can just up and change their licencing and screw you over, something that both of them have done before.

@Plazmaburn


This weekend I’ll be grading a lot of student projects along with doing lecture prep for next week…I may not get to it till mid or late next week, but I made a mock up free hand based on what the part appears to look like based on:
A&K Replacement M249 Feeding Unit
I have no clue what this part does, or how it interfaces with your gearbox…if it even is a gearbox part
But if you can give me the critical dimensions on how to make this item fit, I can attempt to make a 3d model of it for you.
I realize my freehand is a little sloppy, but hopefully you have some experience with drafting and can fill in the various values to make this draft suitable for your needs
I left the through gap (that can be seen in the front) out of the side view because there would have been too many hidden lines whereby making it confusing when you label them, if you fill it out correct on the front and top view, there is no reason that information needs to be repeated on the side view

the one thing that can be problematic is the notch seen in the side view, my hope is you have drafting experience and can correctly describe it so that it can be modeled appropriately, I feel as if that notch is very important for the fitment of this part

please...measurements in metric (.01mm precisions)

@AsianGuy

A hero has appeared!

It has nothing to do with the gearbox. All that piece is, is the feed tube from the magazine to the hopup unit. I'll take some photos of where it will mount and what not.

Orientation of the drawing, the right side is front of gun, and the long side on the bottom is actually the top. Its mounted in the mag well and the keyway interfaces with the lug on the bottom of the hopup unit.

Bullgear CNC Machined Hop-Up for A&K / Cybergun / Classic Army M249 Airsoft AEG, Accessories & Parts, AEG Internal Parts, Hop-Up, M249 Series Hop-Up - Evike.com Airsoft Superstore

It is mounted on an angle in the body of the 249. The cut out section with the feeding nub that is recessed, interfaces with normal m4 mags. Which should give you the approximant size of the unit.

Ok, based on what you shared, I think I got some rough idea of the dimensions, but ultimately I’d still need a lot of them measured by you via caliper in metric.

On the ‘right view’ that notch is where the hopup notch sits, so the angle, length, and depth of that measurement needs to be perfect or you will have feeding issues for sure. (other route is I don't make a notch, and you basically file it out yourself - however that would be a mess with thermoplastics...melting it would be a non-option cause you will warp the whole piece). I foresee this being the biggest of the alignment challenges.

On the ‘front view’ where it supposed to interface with a magazine… I think I can figure out the complementary dimensions based on my own m4 magazines. But I much rather you give me the dimensions (of our intended mag) so that I can make it a “snug” fit (I know m249 are notorious for having bad feeding issues). I am at a lost however at the through cut. Is that what is supposed to “push open” the release mechanism for the spring of the magazine? The way it isn’t angled is what is throwing me off on its purpose. Additionally, how dies the magazine lock into place? Is there another receiving piece I'm not seeing?

Other than that I think knowing the outer perimeter dimensions (front side image) and tapering it so it sits flush with the body is the last of the hurdles

Essentially this is just a magazine to hopup interface, that needs to bring everything into alignment in relationship to the external body

@Plazmaburn


I’m starting to see how it fits in
Are the two screw holes I see in picture 1 and 3 the screw holes on the part? Since it’s screwing in from the top, as you stated previously, the long edge is the “top” of the part

I need what you believe are the dimensions on location I shown in red for proper fitment below. They will be critical towards part fitment and interfacing. If they aren’t accurate, the part won’t fit and the part won’t flush correctly against the hopup, which will lead to sever feeding issues.

Fill in the length of all the red lines (in MS paint if that's easiest for you), I need what you believe are the actual needed length. They have to be shaped in that stairway shape for a reason. Which admittedly I can’t see at this point in time, cause your body does appear to be able to fit just a simple rectangle face base on your picture.

Additionally the hopup diameter (where it sits flush with the part on the right view) and angle between bb feed open and notch needs to be VERY accurate (or you’re going to be pushing bb into a non open face of the hopup)