Off-road ebike swing arm setups

I am going to build a similar bike to the stealth bomber out of aluminium. Has anyone built a homemade aluminium stealth bomber ebike yet?

I can't decide on how to make the bottom bracket. Can you please post your pictures of your bottom bracket/rear swing arm setup's.

Thanks in advance.

Did you only mean for those who own stealth bomber's or anybody with a full suspension e-bike?

Don't use welded aluminum for structural pieces unless you already know about and are prepared to do post weld treatment otherwise you will have to overbuild for required toughness and reliability. Especially if you're posting a thread like this, which implies you are totally unprepared and starting on a whim and can't even formulate a meaningful query.

I know someone who fabricated a Bomber clone from welded aluminum.

If you use the correct alloy there is no heat treat necessary. 7005 comes to mind. 7005 is an aluminium alloy used bicycle frames, due to its relative ease of welding it does not require expensive heat treating - it is however harder to form making manufacture more challenging. Easy weld with skill, good machine, enough gas. 5356 filler. I also like to braze aluminum, very easy.

My entire bike is 7005 and weighs a total of 17lb frame. I have run a violent tire smoking 8000w. I built it on a whim, and it has lasted almost 1000mi by now.

Bicycle building is an art. There are many tools and jigs you may need to do good. One instance is the threads on the inside of the BB. I personally would find a good 7005 donor to build with, cut up and reweld... rather than try to cut the threads on the lathe on the ID of a pipe to fab the bracket.

flat tire said:

Don't use welded aluminum for structural pieces unless you already know about and are prepared to do post weld treatment otherwise you will have to overbuild for required toughness and reliability.

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This.

serious_sam said:

flat tire said:

Don't use welded aluminum for structural pieces unless you already know about and are prepared to do post weld treatment otherwise you will have to overbuild for required toughness and reliability.

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This.

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Lol That^^^. Bah. Whuddevar. Many frames are 7005 I have found.

7005 aluminium alloy
From Wikipedia, the free encyclopedia
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7005 is an aluminium alloy used bicycle frames, due to its relative ease of welding it does not require expensive heat treating - it is however harder to form making manufacture more challenging.
It has an Ultimate Tensile Strength of 350MPa, a Fatigue Strength of 150MPa and a density of 2.78g/cm³ [1] compared to a Ultimate Tensile Strength of 310MPa and Fatigue Strength of 96.5 MPa and a density of 2.70g/cm³ for 6061 aluminium alloy. [2]
It does not need to be precipitation hardened, unlike 6061, but can be cooled in air.[3]
Specific forms of AL 7005 include:
7005-O
7005-T5
7005-T53
7005-T6
[4]



Weld much Sam? Many frames? Evidence of your statements, ...? Perhaps you just did not know the aluminum you were working with, the grade. I empirically know exactly what alloy I weld before I even screw the regulator on and plug the machine in. Exactly. Dont weld Aluminum if you dont know what it is, that would be a novice weldors mistake.

Evidence, perhaps a pic of a frame in 7005 that you have beat on, post weld, with no (0) hardening treatment?
Like say 8000w or more of Tq, speed, and impact loading?

I can. On video if you would like.....


Even gets harder over time lol.. on its own.... 7005 is an awesome metal. Do not fear welding it.

I hate it when someone says " You cant".... esp., if, with some skill, and knowledge, you can.



https://en.wikipedia.org/wiki/7005_aluminium_alloy

My 2c.

The important number is the post weld YIELD strength (not tensile strength, since a relevant goal is presumably to prevent the frame from permanently deforming under use) of the actual welded area since it will be degraded significantly from the yield strength of the base materials, pre weld. The value is usually cut in half if not more.

If you want to really optimize a design and save weight you need to know about the above or things will start breaking before you think.

The problem is that you end up with a sharp gradient of change in temper (strength gradient) across the weld HAZ. It's the equivalent of putting a notch or drilling a hole at that location. And often the welds are in areas of high stress. So you've got high stress, at a stress concentration, through the lowest strength temper. And it's the fatigue strength that really matters. It might not break straight away, but it won't have anywhere near the same cycle life as a properly heat treated part.

If you overbuild in those areas, or if it's in areas of low stress, then fine. Don't worry about it. Overbuild a heavy frame.

DogDipstick said:

From Wikipedia, the free encyclopedia

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Oh yeah, that Wiki page is fully reliable, 100% true. I always reference only a single wiki page whenever I need to justify my existence.

DogDipstick said:

I can. On video if you would like.....

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You keep making this threat, but never follow through.

DogDipstick said:

I hate it when someone says " You cant".... esp., if, with some skill, and knowledge, you can.

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Learn to read. Nobody said "you can't". You missed the salient point of flat tire's post, which I then italicized for emphasis:

flat tire said:

otherwise you will have to overbuild for required toughness and reliability.

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DogDipstick said:

I have run a violent tire smoking 8000w

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Violent :lol:

serious_sam said:

Violent :lol:

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I hear you guys. Is the first bike I fixxed like this but not the first aluminum Ive welded.

Thats it I'm finding a cameraman. F'in still doesnt cease to amaze me what 8Kw and 100?~ ftlbs feels like on an 85 lb bike. Before I break it, right? lol. We will see.

"Ah dont make trets, Ah make promises. " Lol.

Don't let anyone tell you what material to make frames out of. Absolutely meaningless if it is designed correctly. One of the most notably fast and nimble fighter jets of the last half century used plywood as the main structural member holding the wings with near zero issues. As long as you keep flex in check, you will most likely have a long living machine. BTW, 7005 is great stuff.

speedmd said:

Don't let anyone tell you what material to make frames out of. .................used plywood as the main structural member h (F) olding the wings with near zero issues. .........

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The Marines’ Plywood Supply Drone Is Undergoing Flight Tests

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[youtube]RlTNlLjw0gY[/youtube]

Heres some quickies. See me beating on this thing at the end of my driveway...

Welded by an amateur. 750 miles of this so far. Someday I'll do some jumps too and more beating when I get the time and helmet. Lol.

More burnouts and linelocks.
https://www.youtube.com/watch?v=dsCfXrr3jxw
...name's Midnight.
https://www.youtube.com/watch?v=nfGR0mPanvM
... name's Mud.
https://www.youtube.com/watch?v=6i-XzroRRcM
Also named Mud.
https://www.youtube.com/watch?v=TbELX3rOJS4

Playing at the end of the driveway.... (kinda boring).

Doofballin' like a pro on an Ebike.
( please make fun of whatever you want .. Except my lisp, pls. )
https://www.youtube.com/watch?v=ntqyOfnowdg



Long one.. Here im doing burnouts like a kid with a smile ear to ear. This frame is like seriously light as can be for an aluminum bike. Its like a few min long and kinda boring me riding back and forth but someday maybe I'll get all motivated to make a real cool video. ...

I took a long broken frame, made two 20 gram peices of aluminum, welded and braced 10X stronger than the OEM frame that was known for failure at this point.. So much so that Ironhorse decided to redesign the linkage for the rebound cracking was destroying too many Hollowpoint Experts... and solt the modified frame then.

I got a broken one, made two welds and two brazes, used 1/4 x 1/2 x 3" of 7005 attatched with 5653... and...

and proceeded put 20X the human power and 2x the weight on it and 10 hp peaks through the hub. For 750 miles so far.

Cant weld frame? Sure. Especially if you start with new metal it is easy to make enough solid welds.

I'll buy any aluminum frame that I can know the metal and see the fix.. some crack at the bottom bracket and that sucks.. There is no recutting threads on a BB that is on the bike.. and I had to re-mill the bosses for my swingarm. .... when you have to re-machine things in.. that is time consuming.. but adding brazed reinforcement and fixing cracks with filler and 7005 is a possibility for the garage mech.

serious_sam said:

flat tire said:

Don't use welded aluminum for structural pieces unless you already know about and are prepared to do post weld treatment otherwise you will have to overbuild for required toughness and reliability.

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This.

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My bike needs, ZERO (0) post weld treatment. Is strong, stronger than. Is a very strong design.

...about 20 grams of metal per side. Yield and tensile are very intertwined and aluminum was made for that.. and is lightweight. I can do this following all the hobby techniques and being somewhat experienced in welding this and that, learning and reading and practicing.

Lil down the road, lil up the road. I am honestly a lil scared of flipping it anymore like on the two lil wheelies at the end. Its not like a big bike with a clutch. Hey, aluminum bike on a 3.3Kw Kelly has proven to be a whole lot of fun for me, along with being a viable commuter when limited for range.

Qs V1 35H
https://www.youtube.com/watch?v=HMV5SlFN1y4