8020 Aluminum Recumbent Frame?[UPDATE: It works!]

[wyojustin]

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?

 

[spinningmagnets]

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]

Thanks for the input.

 

[John in CR]

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.

 

[Chalo]

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.

 

[spinningmagnets]

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.

 

[Chalo]

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.

 

[John in CR]

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.

 

[wyojustin]

IT WORKS!!!!!!!!!!!!!!

Hey, here is an update on the "VeloRaptor". I built it, and it works great. I already have 300 miles on it commuting to work. Results:
Power: 1300W peak 1100 cruise
Battery: 20 AH 48V with 10AH reserve
Range: 30-50 miles + 10 Mile reserve (did 50 mile town ride on primary battery averaging 20 MPH, faster decreases range)
Max Speed: 35 MPH (up to 40 down hill)

Issues:
Slow start on inclines, prefer 1500W wheel (traditional front type wheel 29er) but having trouble finding it.

 

[ccihon]

That thing looks like a great, simple frame build. It's definitely a "high racer" design - makes me wonder how you mount that thing from a stop, or balance it for temporary stop (tippy toes")? Maybe you never stop! What is the function of the rectangular frame extension that drops straight down just under the seat?

 

[aluminumwelder]

no chain?
80/20 is just as heavy if not heavier than hollow steel tube. I used to use it a lot, but after doing weight analysis found out it is pretty worthless for making bikes out of. ocassional I use very short pieces of it.

 

[wyojustin]

That thing looks like a great, simple frame build. It's definitely a "high racer" design - makes me wonder how you mount that thing from a stop, or balance it for temporary stop (tippy toes")? Maybe you never stop! What is the function of the rectangular frame extension that drops straight down just under the seat?

Thanks @ccihon. I can touch the ground while seated... so problem solved. The rectangular frame houses a large 48V 20AH batttery.

 

[wyojustin]

no chain?
80/20 is just as heavy if not heavier than hollow steel tube. I used to use it a lot, but after doing weight analysis found out it is pretty worthless for making bikes out of. ocassional I use very short pieces of it.

No chain... too difficult to design in. I'm designing this to bolt together, and the aluminum extrussions are very ameanable to alterations. The bike is a bit heavy, but it always will be with a 1200W motor and 20AH battery. It's self powered anyway.

Thanks for checking it out.

 

[ccihon]

So big battery goes there.. Is the small blue box a small battery pack or a controller?

Chains are tough to route on these, long line, generally need idlers etc. Maybe could add front drive approach like this? The headset setup may make this harder. I'm ok if it's not a pedal bike at all!

 

[aluminumwelder]

I'm designing this to bolt together, and the aluminum extrussions are very ameanable to alterations.

True, but you wont' be changing it much once you settle on a final design. 1x3 T slot is 1.333 lbs/ft hollow aluminum tube of same dimension is 0.54 lbs/ft. it's like 2.5x heavier. if you want to save 10 lbs at least change the 2 main long pieces to hollow tube.

 

[wyojustin]

So big battery goes there.. Is the small blue box a small battery pack or a controller?

Just one blue box is all battery. The contoller is about 12" in front of the battery.

Chains are tough to route on these, long line, generally need idlers etc. Maybe could add front drive approach like this? The headset setup may make this harder. I'm ok if it's not a pedal bike at all!

I like that routing.

 

[wyojustin]

Interesting. I think I'd be on board if I knew how to weld. One of these days....