Aluminum Frames?

[RocketeerRat]

Hey guys, theres a ton of ideas floating around in my head right now... I've got a stack of sketches with a vague direction in mind. The critical factor in my current favorite design is the use of aluminum in the frame. I am positive the structure can hold the weight and stress. (I have a aeronautical engineer in the family that I fully intend to annoy) The big question is if I use aluminum for the neck tube and bottom bracket, how obnoxiously thick do I have to use to hold the stresses? The other thought I had was to use a premade steel part but sleeve them inside an aluminum tube as camoflage. I know the old Monark aluminum frames have cracking issues that I would like to avoid, but maybe that was from the casting? If you guys have any thoughts on the subject I'd really appreciate an assist on this. It will be my first scratch frame so I'd love all the help I can get. I'll get some sketches up when I get home tonight.
btw, I want to do an aluminum frame because I'm an aircraft mechanic so I enjoy working with aluminum much more so than steel, and I've rarely seen frames done in aluminum so it might be fun to try something unusual.

 

[JLarkin]

Remember you will be using steel bearing cups in both the headtube and the BB. That in itself will provide stability to the aluminum tubing provided you find the correct size tubing. As for the Monarks, that was 70 year old metallurgy; much more better stuff nowadays. I would guess you will be gusseting all tubing intersections quite well. That will likely be the strength-adder you'll need.

You might want to poke around here. A friend of mine has used this place with good results:

http://www.cycle-frames.com/bicycle-frame-tubing/

 

[karfer67]

the silver kings had issues because the aluminum from what i am to understand was not hardened at all. like now a days when you see aluminum frames they have series of aluminum tubing like 7005.

 

[RocketeerRat]

Remember you will be using steel bearing cups in both the headtube and the BB.

Ah yes, I totally blanked on those! That will certainly help things, this is starting to look possible which I'm actually getting excited about :shock:

Here are a few of my very preliminary extremely rough sketches which are hopefully good enough to give you guys a feel for what I'm after. The first one shows a steel frame that I might have seen somewhere before, but it looks cool, so I drew it. Below that is the sketch that spawned my aluminum idea with the fancy gusset on the headtube. The third is basically a blow up and expansion of that gusset. Lastly is the rear half of the frame detailing how the "tubes" interface with the seat post and BB. I still need to decipher the dropouts and figure out all the actual geometry before jumping into final design. I've heard the 60's AMF that I just picked up has good geometry, and I like it too, so I'm going to steal alot of the layout from that. So far the only actual tubes on the bike are the headtube, BB, and seat post. The rest will be folded and riveted sheets ...can you see my aviation background showing? :lol:
Please let me know what you think, I love getting feedback! Thanks

 

[user 135]

This should be fun to watch.

 

[Dr. Tankenstein]

Agreed.

 

[socal_jack]

Might want to check this out from Ahrens, general aluminum frame building ( e.g 6061 versus 7005 etc) easy to read, big powerpoint type font presentation 18 pages or so. Bottom line you need to heat treat after welding is done.

http://www.ahrensbicycles.com/Aluminum Seminar 2008 NAHBS.pdf

Plus one of the more useful bike accessories ever.

http://www.ahrensbicycles.com/Bottle-Opener.htm

 

[ftwelder]

Hi, I make aluminum bike frames. You will want to construct it from 6061. 7005 is only available in a few different profiles and almost no bar or rounds. If you are planning on welding the frame at all you should heat treat it back up to T6 condition.

I think the last time I made aluminum BB shells in American size (2.062" inside diameter) I think i used 2-1/4X .120 wall. I have a reamer that offers about .005-.010" interference. If you don't ream it or bore it to the correct size, the shell will split.

For the headtube, I would go a minimum of .160" wall. The standard American headtube is slightly smaller than a modern 1-1/8. I don't have any information on the American head tube standard. I would measure the cup and add a 1/4 inch, then go up to the next size. I am guessing you will end up with 1-1/2" X .25 wall, may be .188 wall if you are lucky.