Frame Hole Drilling...

[markz]

Chalo, sir, you mean the world is better off without Walmart!

The bright side is, if this modification scraps the frame, it's only a Wal-bike and the world is better off without it.

 

[docw009]

They often weld an unbraced, open-sided controller box to the bottom bracket shell, and then weld the chainstays to the box instead of to the BB shell. This is one of the highest stress points in a bicycle frame, and they completely screw it up.

E-bike manufacturers do usually have the good sense to make their frames extra heavy, which makes the frames slightly more fault tolerant.

Eek. And I worry about two holes for a bottle carrier. Well, there must be tens of thousands of bikes like this in Chiner.

 

[classicalgas]

The above is actually a pretty good chainstay to BB connection...lots of weld area, plenty of torsional stiffness in th e box for a bike that's never going to see a fit rider torque on the pedals. With bolted on side plates, as shown,it's a far better joint, strength wise, than the typical high end steel road frame. Far heavier. obviously, but it's not likely to fail.

 

[Chalo]

The above is actually a pretty good chainstay to BB connection...lots of weld area, plenty of torsional stiffness in th e box for a bike that's never going to see a fit rider torque on the pedals. With bolted on side plates, as shown,it's a far better joint, strength wise, than the typical high end steel road frame. Far heavier. obviously, but it's not likely to fail.

The side covers are attached with rinkydink little screws that have no structural role to play. So structurally, that box is two parallel plates of aluminum. Not what I'd pick to keep the front and rear halves of my bike working as a unit.

You are right that in practice it probably works acceptably because people who buy these things mostly don't pedal.

 

[PlanetDad]

Well 6 holes drilled and riveted. Didnt get struck by lightning or anything!! :lol:

Blind Rivets are the way to go on the frame. And there were a few things I didn't consider; Support VS Covers. How unforgiving sheet metal is in holding shape.

50 miles and no cracks, or issues. Have a daily max range commute this week that will be the ultimate test, But feel on this frame it will be fine. Wasn't going to post pics, its not pretty at the moment having limited time to design without a toddler 'helping' but see what you guys think so far.


https://drive.google.com/open?id=1giM0NFHMtX9jubjBmZFk6ja0yaXLLk6w


https://drive.google.com/open?id=1AHgjmIYxOI4he8LSa9czaB09789RFgOy

 

[wturber]

Have a daily max range commute this week that will be the ultimate test, But feel on this frame it will be fine.

No, that won't be the ultimate test. That test is putting a few thousand or more miles on the frame.

 

[bergerandfries]

No, that won't be the ultimate test. That test is putting a few thousand or more miles on the frame.

I go through steel Bianchi frames regularly. Just after 10k miles, the Volpe drive side chain stay breaks. I've done it 3 times. And for those whole would comment, yes I use a freehub, not a freewheel, yes I have replaced the rear wheel and drivetrain with each new frame.

I would check the frame monthly. The nice thing about steel that I've noticed, is that when it fails, a crack shows LONG before failure. Frankly, everyone should be checking their frames monthly, no matter the material or if you drilled holes or not.

 

[PlanetDad]

Have a daily max range commute this week that will be the ultimate test, But feel on this frame it will be fine.

No, that won't be the ultimate test. That test is putting a few thousand or more miles on the frame.

Few thousand miles off a $1k, just fine IMO.

Question is how, and when failure happens.

 

[PlanetDad]

Have a daily max range commute this week that will be the ultimate test, But feel on this frame it will be fine.

No, that won't be the ultimate test. That test is putting a few thousand or more miles on the frame.

Few thousand miles off a $1k build, just fine IMO.

Question is how, and when failure happens.

 

[classicalgas]

"The side covers are attached with rinkydink little screws that have no structural role to play. So structurally, that box is two parallel plates of aluminum. Not what I'd pick to keep the front and rear halves of my bike working as a unit."

Those are, at minimum, 5mm screws. Even cheesy Chinese no grades will allow torque high enough to shift the sheer loads off the screws and into friction between side plates and box . Any realistic load (chain tension under pedaling) will be primarily compression/tension across the long sides of the box, anyway, not torsional loads. You really think that box is less strong/reliable than the hinge of a folding bike? More prone to failure than the high end steel frame mentioned earlier?

 

[docw009]

The side covers are attached with rinkydink little screws that have no structural role to play. So structurally, that box is two parallel plates of aluminum. Not what I'd pick to keep the front and rear halves of my bike working as a unit.

It's cast as a 5 sided box, with one side open. I suppose the 4 tapped holes in the four corners for the cover are going to create stress points, but the box is more than two parallel plates. It's also a folding bike so there will be a lot of things to flex. Frame hinge. Stem hinge.

 

[Chalo]

The side covers are attached with rinkydink little screws that have no structural role to play. So structurally, that box is two parallel plates of aluminum.

It's cast as a 5 sided box, with one side open. I suppose the 4 tapped holes in the four corners for the cover are going to create stress points, but the box is more than two parallel plates.

The one of those bikes I de-electrified had an insubstantial side plate on both sides. The welded-in part appeared to be a chunk of extrusion, open on both ends.

It would have been better, structurally speaking, to have one closed end, but that wasn't the case.