Open Source Spaceframe recumbent bike build

  • #1
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0

Main Question or Discussion Point

Okay, so I'm new to this forum, but I'm hoping I can get some help. I live in the United States, and I'm having trouble converting from metric to standard with the build plans given. I want to build the open source Spaceframe recumbent bike which the build plans can be found here http://www.n55.dk/manuals/spaceframevehicles/DIY.pdf The problem, the entire build plan is in metric, and I'm not sure about the best method to go about converting metric build plans to standard.

Specifically, the build plans ask for 25mm square aluminium tubing with 2mm material thickness. Can someone maybe point me in the right direction as to how I should go about this build? Can I buy these materials at say Home Depot that would be the same size?

Thanks for any help I receive. I have no degree in any kind of mechanical engineering, and I've only taken a beginners level physics course in college. I'm building this bike, because recumbent bikes are out of my price range to buy outright. This open source design is supposed to be strong, cheap, and effective.
 

Answers and Replies

  • #2
berkeman
Mentor
56,843
6,825
Okay, so I'm new to this forum, but I'm hoping I can get some help. I live in the United States, and I'm having trouble converting from metric to standard with the build plans given. I want to build the open source Spaceframe recumbent bike which the build plans can be found here http://www.n55.dk/manuals/spaceframevehicles/DIY.pdf The problem, the entire build plan is in metric, and I'm not sure about the best method to go about converting metric build plans to standard.

Specifically, the build plans ask for 25mm square aluminium tubing with 2mm material thickness. Can someone maybe point me in the right direction as to how I should go about this build? Can I buy these materials at say Home Depot that would be the same size?

Thanks for any help I receive. I have no degree in any kind of mechanical engineering, and I've only taken a beginners level physics course in college. I'm building this bike, because recumbent bikes are out of my price range to buy outright. This open source design is supposed to be strong, cheap, and effective.
Welcome to the PF.

I would think you should be able to get metal stock in metric sizes at most metal supply houses. Have you tried searching in your area for Metal Supply House or similar?
 
  • #3
Danger
Gold Member
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244
Keep in mind also that for a bike the tolerances aren't critical. If you just use a standard conversion chart and happen to be out by .01", nobody will notice. Anything where clearances are important such as hubs will be prebuilt to spec anyhow.
 
  • #4
Baluncore
Science Advisor
2019 Award
7,435
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You can use inch dimensioned material. As a guide, use the following translations.

Bolts;
For M6 use 1/4”
For M8 use 5/16”

Aluminium;
2mm is 0.08”
3mm is 1/8” (= 3.175mm)
3.5mm use 1/8” or 5/32”
4.0mm is 5/32”
22 mm is 7/8”
25 mm is 1”
30 mm is 1.25”
60 mm is 2.5”
 
  • #5
2
0
You can use inch dimensioned material. As a guide, use the following translations.

Bolts;
For M6 use 1/4”
For M8 use 5/16”

Aluminium;
2mm is 0.08”
3mm is 1/8” (= 3.175mm)
3.5mm use 1/8” or 5/32”
4.0mm is 5/32”
22 mm is 7/8”
25 mm is 1”
30 mm is 1.25”
60 mm is 2.5”
This is helpful, thanks. I managed to find a fairly cheap Aluminum square tubing on the Home Depot website which had similar dimensions. I'll keep this thread updated on the progress, and hopefully receive more help that will most likely be needed.
 
  • #6
Danger
Gold Member
9,607
244
Looking forward to it. I might not be of any assistance, but that's never stopped me from chirping up before and it won't now.
 

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