8020 Aluminum Recumbent Frame?

A place to discuss the repair, design, and customization of the bicycle itself, not the powertrain ( battery, controller, motor, etc ).
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wyojustin   1 µW

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8020 Aluminum Recumbent Frame?

Post by wyojustin » Apr 18 2021 8:10am

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Looking for feedback designing a frame for a recumnant e-scoot design. This design uses off the shelf parts wherever possible: headset, fork, wheels, seat, tiller steering, dropouts.

Here is a link https://bit.ly/2QDFdpR to the components used.

Any advice on the AL?

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spinningmagnets   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by spinningmagnets » Apr 18 2021 12:11pm

The two common Al alloys are 6061 and 7075

6061 is easy to TIG weld, 7075 very difficult to weld (6% zinc, 2.3% Magnesium, 1.4% copper)

7075 is stronger, similar to soft steel. 6061 is easier to bend without cracks (more ductile)

If you plan to drill and bolt (possibly bond with DP-420 epoxy), 7075 is stronger.

Soft metals like brass and 6061 aluminum actually drill easier with slightly dull bit. The sharp new bits dig-in too much.

(this post has been edited multiple times to correct bad info)

wyojustin   1 µW

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Re: 8020 Aluminum Recumbent Frame?

Post by wyojustin » Apr 18 2021 12:53pm

Thanks for the input.

John in CR   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by John in CR » Apr 23 2021 10:38am

Recommending use of a dull cutting tool is one of the strangest things I've heard on the forum. Yes aluminum and brass drill differently because they are softer and more ductile, so significantly higher rpm than used to drill steel is recommended.

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Chalo   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by Chalo » Apr 23 2021 12:03pm

John in CR wrote:
Apr 23 2021 10:38am
Recommending use of a dull cutting tool is one of the strangest things I've heard on the forum. Yes aluminum and brass drill differently because they are softer and more ductile, so significantly higher rpm than used to drill steel is recommended.
Sharp tools work best on aluminum (with adequate lubrication), but *slightly* dulled cutters work best on yellow brass. Very sharp drills are more prone to seizing up, and sharp endmills and reamers chatter and squeal more.

A drill with a rounded-off or burned cutting edge isn't good for any material.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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spinningmagnets   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by spinningmagnets » Apr 23 2021 12:19pm

All good info. When I said "slightly" dull, it's hard to quantify. I definitely agree that if its "too dull" that's bad.

Take two new drill bits of a bolt size that you plan to use (*1/4-inch, 6mm, etc), use one to drill a hole in 1/8th inch mild steel.

Then try both bits to drill one hole each in the type of aluminum you plan to use. If the newer bit works great, then no "dulling" needs to be done.

I am a huge fan of using "tap magic" fluid when drilling steel, and,...since the boss was paying for it, we also bought a can of tap magic that was specifically made for drilling in aluminum/brass/copper, etc. All the softer metals.

I have heard that in a pinch, a 50/50 mix of ATF and acetone works (transmission fluid, nail polish remover). I have not verified this on steel or aluminum yet.

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Chalo   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by Chalo » Apr 23 2021 2:07pm

I prefer Lubegard Bio-Tap cutting fluid to chlorinated oils like Tap Magic or A-9. Bio-Tap works great on all common metals and washes off quickly with water.

For aluminum, both Dawn dish detergent and WD40 work excellently, so there's little reason to spend extra in that case. Machining operations on yellow brass usually work great when dry.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

John in CR   100 GW

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Re: 8020 Aluminum Recumbent Frame?

Post by John in CR » Apr 23 2021 2:31pm

Chalo wrote:
Apr 23 2021 12:03pm
John in CR wrote:
Apr 23 2021 10:38am
Recommending use of a dull cutting tool is one of the strangest things I've heard on the forum. Yes aluminum and brass drill differently because they are softer and more ductile, so significantly higher rpm than used to drill steel is recommended.
Sharp tools work best on aluminum (with adequate lubrication), but *slightly* dulled cutters work best on yellow brass. Very sharp drills are more prone to seizing up, and sharp endmills and reamers chatter and squeal more.

A drill with a rounded-off or burned cutting edge isn't good for any material.
Thanks for the info on working with brass, since I regularly make bushings with it. I guess my buddy's carbide set of metric bits that I use are somewhat dull due to age as I've never had any issue with brass. I do use the lathe to hold the piece of stock in the chuck, so the bit doesn't spin on whatever that piece of the lathe is called, which holds a drill chuck or centering point). The thing that hold cutting tools is the chariot...I think.

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