Options to reinforce frame drop outs?

D

Darth Yoda

New Member
Hi. My brother got a little hastened by getting into our garage for the first time and amongst other things dropped my aluminum frame by the drop outs on the concrete floor. There is no visible damage but the whole thing got me thinking about options to reinforce the dropouts, partly becouse of the hit but also in general. My drop outs are part of the frame. What are the options here?
 
Generally, we advise a steel frame.
Common news from the aircraft industry is catastrophic failure of aluminum parts due to metal fatigue causing stress cracks and failure, with no warning.
Good luck!
rc

and I know that's a big negative... sry.
 
I used to feel that way to rusty, however I have had builds using carbon fiber mountain bike frames and and also aluminum mountain bike frames, cruisers aluminum makes me nervous because they are not built for abuse. however the better mountain bikes are made to take a beating. I actually think they take a heck of a harder beating riding trails and stuff then we ever give them on our motorized bicycles. my electric mountain bike I beat the piss out of it. taking jumps everything however my aluminum cruiser I even slow down for speed bumps on the road, it is longer then a mountain bike frame and I do not think it is made for any abuse
 
I wouldn't doubt that for a minute, Paul ! lol

I suppose I should hedge a bit and make a provisional retraction...

I'm sure some are made for abuse and will hold up for a long time with considered use...

However, unlike steel frames which will most likely crack and bend before total failure, aluminum and carbon fiber will possibly give no warning when they fail.

How's that?
:-)
rc
 
i agree 100%. sad thing is i do not know of any quality steel bikes being made now. the older ones are like tanks though
 
paul said:
i agree 100%. sad thing is i do not know of any quality steel bikes being made now. the older ones are like tanks though
Click to expand...
Really? Felt steel framed cruisers are great quality. Look at scotto's unmodified $250 Felt Bixby which is powered by a 20 HP 212cc motor and raced hard.
Just got back from the PO on my pedal Felt V12 coaster brake bike that will get a motor. It is rock solid.

There are other inexpensive steel framed cruiser bikes out there that are plently strong and will take a gas motor just fine.
The Target Schwinn Jaguar is a good example of a cheap strong steel framed bike. Just look at 2doors bikes.
 
rustycase said:
Generally, we advise a steel frame.
Common news from the aircraft industry is catastrophic failure of aluminum parts due to metal fatigue causing stress cracks and failure, with no warning.
Good luck!
rc

and I know that's a big negative... sry.
Click to expand...

"We"? o.O

As has been mentioned previously, it isn't so much the material but rather the quality of construction - "steel" won't save you from shoddy welds and substandard parts.

For every report of aluminum failure there's at least ten times that regarding steel - does that make steel hazardous? Of course not, rather steel is simply the more commonly used material in the cheapest of bicycles.

Every material has it's advantages and disadvantages, aluminum no exception - but I must say referencing the extreme duress of aviation would serve as a recommendation rather than a caution against, a failure to inspect doesn't constitute a "no warning" scenario and the "fatigue" experienced is caused by conditions so far in excess of anything possibly applicable to our bicycles that the very fact they continue to use it is good enough for me.
 
It has been proven that aluminum can be every bit as tough and strong as steel IF DESIGNED for the application.
Steel frames have a better safety margin when subjected to the extreme vibration a motor causes than aluminum frames.
The high frequency of two stroke vibes seems to affect aluminum more than four strokes, and can cause failures that pedal use would never cause.
Just my two cents, but I prefer steel for ht builds.
I would use aluminum for a four stroke with no worries aside from normal vigilance.
 
as far as reinforcing drop outs you may wish to use a technique used by frame builders to strengthen / stiffen rear stays where disk brakes are used:

Disc%2Bbrake%2Bmount.jpg


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carbon example (looks like a pretty dope carbon cross bike :P)

IMG_8903.jpg


you could do this to both sides of the frame - adding triangulation makes a frame MUCH stronger.
 
It's also the grade (quality) and source of the metal that makes a difference between a good frame and a not so good frame.

As far as aluminum, I am sure the more expensive mountain bikes use a different grade of aluminum than the aluminum cruiser bikes.

Most of the older steel frames are good for motorized bicycle. Just be aware that some older frames, like Huffy, had pressed fitted and spot welded chainstays. I don't think I'd take a chance without having some brazing or welding done on the chainstays.

Reinforcing the dropouts on aluminum? You could probably find someone to weld, but without heat treatment, you'll probably have more problems down the line.

Go with steel and you should have no problems with having the chainstays reinforced.

Chris
AKA: BigBlue
 
BigBlue said:
It's also the grade (quality) and source of the metal that makes a difference between a good frame and a not so good frame.

As far as aluminum, I am sure the more expensive mountain bikes use a different grade of aluminum than the aluminum cruiser bikes.

Most of the older steel frames are good for motorized bicycle. Just be aware that some older frames, like Huffy, had pressed fitted and spot welded chainstays. I don't think I'd take a chance without having some brazing or welding done on the chainstays.

Reinforcing the dropouts on aluminum? You could probably find someone to weld, but without heat treatment, you'll probably have more problems down the line.

Go with steel and you should have no problems with having the chainstays reinforced.

Chris
AKA: BigBlue
Click to expand...

Heat treating is everything with aluminum. You should NEVER weld on aluminum bike frames unless you KNOW the alloy used and how welding heat will affect strength.
Adding gussets to aluminum frames can weaken them more than it reinforces unless done correctly by an experienced welder.
Just my opinion from 30+ years welding.
 
But i remember seeing some kind of safety a while ago on the net, on a fork it should be said, that had either a joint or a spring in it's desgin. Does this ring any bells?

I will have an electric motor by the way, maybe that takes away most if not all of the vibrations on the frame?
 
Okey i found it now, they're called Torque Arms. Does anyone know if they can be used on the rear in some way, or another solution?

Thanks.
 
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