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STL Design files-help needed

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TRFfan

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Hi,

These fin guides i got made by someone at shapeways, but it turns out they are the wrong dimensions, the OD of the body tube is 24.8 but its actually supposed to be 25.4 mm. Can someone help me out by redesigning it? Thanks,

View attachment 316016
 

timbucktoo

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Contact shapeways and tell them the fins they made aren't right!
 

TRFfan

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There is also a nose cone i need redesigned, length is 150mm but i need it to be 220mm, base diamiter is 24.8 but i need it to be 25.3 mm, wall thickness of shoulder is 1.5 mm but i need it to be 1mm (and the length of the shoulder has to be 15mm), wall thickness of nose cone is 2.5mm but i need it to be 2mm. If necessary you can charge me for it by design time.
 

TRFfan

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Contact shapeways and tell them the fins they made aren't right!
Well the guy who was making it for me messed up alot of times, i told him to make fin guides and he ended up making something completely different and he did this with alot of things. I told him about the fin guides and he ended up charging me money for his mistake. So i dont really want to do business with them again.
 

EXPjawa

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Everything that I've had done through Shapeways has been spot-on. What I have learned, though, is that an STL file is essentially unitless. So when it is imported into whatever print software is used, it doesn't come in at a fixed size. It is possible that needs to be scaled properly to print at the correct size. It could be that there was related error either on their end or when you created the file. I will attempt to import your file and see if I can spot the issue.
 

TRFfan

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Everything that I've had done through Shapeways has been spot-on. What I have learned, though, is that an STL file is essentially unitless. So when it is imported into whatever print software is used, it doesn't come in at a fixed size. It is possible that needs to be scaled properly to print at the correct size. It could be that there was related error either on their end or when you created the file. I will attempt to import your file and see if I can spot the issue.
It isnt shapeways that is the issue, i went to their designer directory and thats where i found that guy. I dont want to try again with them since i lost about 200$ USD in that transaction for files that werent even made properly.
 

EXPjawa

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I guess I'm confused how you went to Shapeways and the part was printed wrong, but it wasn't Shapeways that did it...
 

EXPjawa

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Gotcha. Unfortunately, I was able to import the STL into my CAD system, but can't actually do anything to it or put dimensions on it even. Can you give the basic specs (size, thickness, fin width, tube it fits)?
 

TRFfan

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Gotcha. Unfortunately, I was able to import the STL into my CAD system, but can't actually do anything to it or put dimensions on it even. Can you give the basic specs (size, thickness, fin width, tube it fits)?
Oh ok. The fin span is 20 mm, root chord is 60 mm, thickness is 1/32", tube diamiter is 25.3 mm.

Thanks!
 

EXPjawa

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What was the overall length and width of the fin guide as previously designed? I assume that by "fin span", you mean span from the tube (because an overall span of 20mm is smaller than the tube diameter), correct?
 

TRFfan

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Yeah fin span is the fin height (how high one fin is above from the tube). The origanal fin guides were square and about 75*75 mm.
 

EXPjawa

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OK, try this file. It isn't exactly the same, as I freestyled the X, Y & Z numbers of the basic plate, but the form within should be to your spec of 25.4mm diameter, accomodating four 20 x 0.79mm thick fins. No promises that it will be trouble free, but if the sizes need revising, let me know. FYI - it was drawn in inch units, which means it'll have to be uploaded to Shapeways in inches. If you select mm, it'll be 1/25.4 scale...

View attachment FINGUIDEFILE01.stl
 

TRFfan

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OK, try this file. It isn't exactly the same, as I freestyled the X, Y & Z numbers of the basic plate, but the form within should be to your spec of 25.4mm diameter, accomodating four 20 x 0.79mm thick fins. No promises that it will be trouble free, but if the sizes need revising, let me know. FYI - it was drawn in inch units, which means it'll have to be uploaded to Shapeways in inches. If you select mm, it'll be 1/25.4 scale...

View attachment 316021
ok thanks!
 

TRFfan

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There is also a nose cone i need redesigned, length is 150mm but i need it to be 220mm, base diamiter is 24.8 but i need it to be 25.3 mm, wall thickness of shoulder is 1.5 mm but i need it to be 1mm (and the length of the shoulder has to be 15mm), wall thickness of nose cone is 2.5mm but i need it to be 2mm. If necessary you can charge me for it by design time.

Thanks!
 

EXPjawa

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I may be able to do something this week at some point on my lunch when I'm at work, but there's not a lot I can do over the weekend... Since I can't open your STL from here, and I don't have OR to open your ORK, why don't you also state what shape the cone is to take (conical, ogive, elliptical, etc). Also, you'll need to specify the shoulder diameter, since you've only given its length and wall thickness.
 

DavidMcCann

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It isnt shapeways that is the issue, i went to their designer directory and thats where i found that guy. I dont want to try again with them since i lost about 200$ USD in that transaction for files that werent even made properly.
there's gotta be at least a half dozen guys here with printers who would have printed 20 of each part for that price...
 

dcullen

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there's gotta be at least a half dozen guys here with printers who would have printed 20 of each part for that price...
Amen to that. I'd do them cheap, but shipping to Canada is a pain. Check out 3dhubs.com for getting connected with printers in your area. Looks like there are more than a few in Canada. Prices should be much more reasonable. And is there a chance that there is a printer available for you to use, perhaps at school or a library? Sell the use as STEM/engineering related. Also checkout www.thingiverse.com for an excellent selection of model rocket parts, many of them are parametric - that means you can set the sizes and the customizer will create a model to your specs
 

dcullen

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There is also a nose cone i need redesigned, length is 150mm but i need it to be 220mm, base diamiter is 24.8 but i need it to be 25.3 mm, wall thickness of shoulder is 1.5 mm but i need it to be 1mm (and the length of the shoulder has to be 15mm), wall thickness of nose cone is 2.5mm but i need it to be 2mm. If necessary you can charge me for it by design time.

Thanks!
OK some questions and assumptions. 25.3 is an odd diameter for a body tube, I'll assume some heavywall bt50 or fiberglass or some other tubing. And then 23.3 mm diameter by 15mm for the shoulder. That is a very short sholder. Ogive shape 220 mm from shoulder to tip. Thats a greater than 10x1 ration. Do you need the internal thread?
 

dcullen

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Here's a first pass for the shape. Note that with a 220mm length + 15mm shoulder you're looking at a total length of 235mm, which is beyond my ability to print (currently, until the FT-5 kit arrives)View attachment Test Nosecone.stl
 

TRFfan

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I may be able to do something this week at some point on my lunch when I'm at work, but there's not a lot I can do over the weekend... Since I can't open your STL from here, and I don't have OR to open your ORK, why don't you also state what shape the cone is to take (conical, ogive, elliptical, etc). Also, you'll need to specify the shoulder diameter, since you've only given its length and wall thickness.
The shoulder diamiter is 24mm and the nose cone shape is von karman.

there's gotta be at least a half dozen guys here with printers who would have printed 20 of each part for that price...
I know that guy charged to much.

Amen to that. I'd do them cheap, but shipping to Canada is a pain. Check out 3dhubs.com for getting connected with printers in your area. Looks like there are more than a few in Canada. Prices should be much more reasonable. And is there a chance that there is a printer available for you to use, perhaps at school or a library? Sell the use as STEM/engineering related. Also checkout www.thingiverse.com for an excellent selection of model rocket parts, many of them are parametric - that means you can set the sizes and the customizer will create a model to your specs
OK some questions and assumptions. 25.3 is an odd diameter for a body tube, I'll assume some heavywall bt50 or fiberglass or some other tubing. And then 23.3 mm diameter by 15mm for the shoulder. That is a very short sholder. Ogive shape 220 mm from shoulder to tip. Thats a greater than 10x1 ration. Do you need the internal thread?
I dont need the internal thread but the only reason why my nosecone is so long is because i need to fit the telemini antenna. And the shoulder is not that long because i want to keep the body tube length down.
 

dcullen

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Assuming your intent is to pursue the G altitude record you may want to check this out

https://www.apogeerockets.com/Rocket_Books_Videos/Pamphlets_Reports/Tech_Pub_5

Maximum altitude is more complicated than putting the largest motor in the lightest rocket. There are optimum weights, diameter to length ratios, etc.

I also note that you indicate the tracker antenna passing through a tunsten slug, any metal in the area of the antenna will attenuate your signal.

Good luck
 
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