Bought a used homemade recumbent, am told it is aluminum, got it home,rode for awhile. Noticed creaking coming from crank area,looked and found crack
where crank connects to frame (see pic). Did not notice when I bought it! Can this be repaired or am I stuck with it?
Already have 325.00 into bike. Seller can not be found!

Looks like a typical weld bead edge crack. You say the bike is home made. Any idea as to the grade of Alu or construction process done (like heat treating)? As to the repairability- first you'd want to know the Alu series used so the after welding concerns could be evaluated. Then a "qualified" fabricator could weld on to the main frame tube a new BB/stand off, and then do any heat treating/aging needed. The skill of the welder is the big issue.

But I'll add a few coments- First is that the joing that failed is not the highest stressed one on the bike, or the most catastrophic results, in failure, one. The frame shows a classic recumbent frame design lack of triangulation. The main frame tube to chain stay area is a big question in my eyes. The section from the cracked joint to the head tube is also a concern. Given the failure of the weld at the BB stand off/main frame tube I'd wonder about the other joints.

Really try to chase down the seller. Besides the info he might be able to tell you about the construction he should have some skin in the deal too. If he were to tell you who welded the bike and that you should go to that guy for the fix... head the other direction fast. At only $325 in the bike, the leason is not too expensive for now. The parts are still good (I assume) for transfer to some other bike. I'd strongly consider moving on to something else. Andy.

I see rust. Does a magnet stick to it?

Kinda surprised that weld above the front derailleur hasn't exploded yet, to be perfectly honest

Holy Cantilevered design! That thing looks like it'd fall apart under anyone north of 70 lbs...

I don't know- it looks like steel to me. Take a magnet to it. If the joint that cracked was not welded any better than the one above it, it's no wonder it's broken. The design is not good and you'll be fixin' that thing for most of it's "short" life. To bad you can't hunt down the seller if for no other reason than to tel him he shouldn't be selling stuff like that.

yea, wish i could find him! A magnet sticks to it!

Fully agree with Andrew's comments. Also noting the rather ragged looking weld on the joint just above the cracked one. Looks like the entire effort would best be hidden away to protect the guilty. Recommend cutting it into about 3-4 parts and put in recycle bin. If not cut up someone will pull it out, built in up and be put at risk. At least there are a lot of parts to reuse as suggested.

I should have seen the small weld bead and the braze on as well to figure out it is steel. (It is so easy to read into a situation what you've been prepped to see). But my advice doesn't change much except the reference to heat treating the "ALU" after welding. Being steel it does open up the range of possible repair methods (brazing or welding). Still not sure if it's worth that though. Andy.

bike is gone...thanks for all the input and info......