Pay it forward.

[Shield Arc]

A friend of my wife ask me if I would help her son-n-law with a project. He is in his senior year to be a mechanical engineer. This is his senior year project. Make a collapsible bicycle frame out of aluminum pipe. This is all we got done so far. Personally I don't think it will telescope in with out pivot points. But who am I? I can't even spell engineer.

 

[davesl708]

I agree. The front top bar and bottom angle bar have no place to go unless disassembled. I hope that is aircraft grade tubing. There are eight load points on that frame not counting the telescoping sections.

Good luck.

Nice welding by the way. That part looks good.

 

[bcp]

A triangle with rigid angles will telescope using 3 sides at the same time. Just 2 sides telescoping won't work. The 3rd side has to get shorter, too.

Bruce

 

[Shield Arc]

He has made a few miscalculation so far. He said the first cope he made by hand took him 45-minutes. I showed him how to do it with a hole saw. He about fell over! :laughing:

 

[bcp]

Things would be much easier if more engineers got involved with the construction or maintenance of what they design.

Bruce

 

[Shield Arc]

I get the biggest kick out of these kids. Things we take for granted, they think is the coolest thing ever.:laughing:
This kid has no idea how to hands on build anything.

 

[aczlan]

A triangle with rigid angles will telescope using 3 sides at the same time. Just 2 sides telescoping won't work. The 3rd side has to get shorter, too.

Looks like that is being done for the front triangle, the seatpost and the other two bars all telescope...

Aaron Z

 

[davesl708]

Looks like that is being done for the front triangle, the seatpost and the other two bars all telescope...

Aaron Z

That is correct but there needs to be two pivot point at the front fork tube for this design to work. Top and bottom tubes will need to pivot.

 

[bcp]

There are many versions of a logo with a 3 gear train symbolizing working together, etc. I'm hoping it is an artist's goof, not an engineer's.



Bruce

 

[Shield Arc]

That is correct but there needs to be two pivot point at the front fork tube for this design to work. Top and bottom tubes will need to pivot.

That's the way I see it too. But I'm just a rigger, sometimes weldor.

 

[chad22]

That's an interesting project.

 

[RedNeckGeek]

Personally I don't think it will telescope in with out pivot points.

At first glance I thought the same thing. But once I was able to open the first two images side by side, it seems like it should work if all three tubes can be made to collapse simultaneously. The finish on the ID and OD better be pretty good to do that, because if the tolerances between the ID and OD are made large to let them slide against each other, there'll be so much slop the frame will lose rigidity.

I'd be more concerned with the direction of the front hinge in the chain stays. It will tend to open under load, so it better have a strong locking mechanism.

When I was going to school, I held summer and part time jobs in a state highway materials testing lab, at a nondestructive testing company, as a welder in a truck body shop, and stocking shelves at K-Mart. Guess which ones made it onto the resume I sent out at graduation time?

I also took all the shop classes that were available in junior and high school, as well as a night time welding class at a local vocational college. By the time I landed my first engineering job with GE, I could read mechanical drawings (including weld symbols) and electrical schematics, run a lathe and mill, weld with GMAW, GTAW, and SMAW, and write a decent technical paper. In later years, the vast majority of new engineers we hired had NO hands on experience because by the time they hit junior and high school, all the shop classes had been fazed out (too expensive) and all the engineering classes taught only theory. The hazing that resulted on the shop floor made for many amusing moments, but the screw ups in the design department were no laughing matter.

I'm sure you've seen the same in your career, and know what you're doing for this young man is as valuable as anything he's been taught so far, and probably more. Looks like you're doing the welding (it's beautiful BTW), but I hope he gets a chance to try his hand with the torch as well as the cranks before he's done with his project.

Please keep us posted on progress. I'm curious to see how it turns out!

 

[aczlan]

That is correct but there needs to be two pivot point at the front fork tube for this design to work. Top and bottom tubes will need to pivot.

As I see it, the angles for all three corners can stay the same as long as all three sides of the triangle can shorten in unison (which it looks like they can per http://www.tractorbynet.com/forums/files/welding/414321d1425159143-pay-forward-frame-2-jpg).

Here are 3 nested triangles, the outer one is has 3.5" sides for the top sides, the middle one has 2" sides and the inner one has 1" sides, the angles between the lines are the same on all three triangles:


Aaron Z

 

[Shield Arc]

I hope he gets a chance to try his hand with the torch as well as the cranks before he's done with his project.

Yeah, I want to get him behind the hood and welding before this is completed. I can tell this kid is a sponge, he is just amazed at how I'm building this frame. It's easy to see he has never got his hands dirty before. I think this is a real good experience for him.

 

[cormier]

Things would be much easier if more engineers got involved with the construction or maintenance of what they design.

Bruce

I agree with you 100% everything always looks good on a drawing but put it to practice???? Us bottom feeders Millwrights at our plant have to fix their miscalculations and they still get the credit for the whole job haha the way things work.

 

[Arc weld]

Yeah, I want to get him behind the hood and welding before this is completed. I can tell this kid is a sponge, he is just amazed at how I'm building this frame. It's easy to see he has never got his hands dirty before. I think this is a real good experience for him.

And you're just hating doing it aren't you.:laughing:

 

[Shield Arc]

I agree with you 100% everything always looks good on a drawing but put it to practice???? Us bottom feeders Millwrights at our plant have to fix their miscalculations and they still get the credit for the whole job haha the way things work.

He has made some miscalculation, he didn't allow enough room for the wall thickness of these couplings. I tried to shave the wall thickness out of the aluminum pipe. But got afraid I was going to cut through. So we had to add more pipe, so the couplings would clear each other.

And you're just hating doing it aren't you.:laughing:

Arc weld I love the look on his face, like Christmas morning! :laughing:

 

[s219]

I get the biggest kick out of these kids. Things we take for granted, they think is the coolest thing ever.:laughing:
This kid has no idea how to hands on build anything.

That's a bit scary for an ME, but very common. During freshman year in college, I was horrified to find that a large percentage of my ME classmates were not mechanically inclined in the least. Many of them made good engineers after all, but the best ones (by far) were kids who had hands-on ability or some sort of existing mechanical talent.

I remember the first time I saw a lab in the machine shop, where I worked part time. It was downright scary how little skill most students had, and by scary I mean dangerous. I remember one kid launching pieces of bar stock out of a milling machine vise -- thought he could machine several pieces at once by clamping them together, but of course as soon as the cutting tool hit the metal, the middle pieces shot out like missiles. That kid got dragged out of the shop by his earlobe.

 

[murphy1244]

That's a bit scary for an ME, but very common. During freshman year in college, I was horrified to find that a large percentage of my ME classmates were not mechanically inclined in the least. Many of them made good engineers after all, but the best ones (by far) were kids who had hands-on ability or some sort of existing mechanical talent.

I remember the first time I saw a lab in the machine shop, where I worked part time. It was downright scary how little skill most students had, and by scary I mean dangerous. I remember one kid launching pieces of bar stock out of a milling machine vise -- thought he could machine several pieces at once by clamping them together, but of course as soon as the cutting tool hit the metal, the middle pieces shot out like missiles. That kid got dragged out of the shop by his earlobe.

I seen a guy cutting or trying to on the wrong side of a band saw. He quit months later.

 

[Shield Arc]

Welp, I was wrong! It does collapse. He had to get back over the mountains for class tomorrow morning. So we'll finish it off next week end. I sent him home with some 100, and 320-grit emery cloth to clean the pipe up better. Along with a round, and flat mill file to take care of any burrs.


Did get him to play with the Dynasty a little bit. Pretty quick learner.