Aluminum Frame or Steel Frame?

Discussion in 'Motorized Bicycle General Discussion' started by Patr1ck, May 25, 2010.

?

Which do you like better?

Poll closed Jun 4, 2010.
  1. Aluminum Frame

    4 vote(s)
    26.7%
  2. Steel Frame

    11 vote(s)
    73.3%
  1. taddthewadd

    taddthewadd New Member

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    I thought I should mention this about aluminum and weight. A cheap walmart or target aluminum frame usually weighs more than a good steel frame. On those cheap aluminum frames they use a cheap (heavy) alloy which requires thicker tubes and huge down tubes. Only when you get into 1,300 and up aluminum bikes do you get a lighter/stronger frame. So if you think you are saving weight and that is the deciding factor on going aluminum don't go cheap. You will be much better off with a chromoly frame off of craigslist. The kit will fit better, it is stronger, and absorbs vibrations better.
     
  2. wildemere

    wildemere New Member

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    Damn Straight, Tad, At this time Chrome Moly Steel is the best for me.

    Even the best quality aluminium frames have high failure rates under heavy duty use.

    A Titanium frame would be nice to experience though.

    One day maybe...
     
    #22 wildemere, May 26, 2010
    Last edited: May 26, 2010
  3. kicking

    kicking New Member

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    I went on an tour at Reynolds aluminum years ago. And I saw an race car that was awesome ! It was an Shelby I think. I don’t think aluminum is not a very good engine. But I will say the quality of things we buy now are ‘junky’ and poorly made. When we drink water from our tap’s we have either copper or pex . I have pex and love it! don’t worry so much about winter freeze up and soldering . I bet they slip tin in the mix of copper since it is scarce. I have an cage around my out door central air so my copper wont get ripped off , sad huh? But I love my ‘ next: bicycle and would take nothing else , for this wally world bike ! It is Premiere 6061 aluminum. A word of caution about wall mart bikes. They are nice for the poor folks and are nice. But a lot of the rims are either bent or warped or something : ‘do I have an witness‘?
     
  4. Technocyclist

    Technocyclist Motorized Bicycle Senior Technologist

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    Steel frames... it'll lasts longer... I've seen aluminum frames break up in so many different places. Seat Stays, down tube, and Head tube.... Aluminum tends to crack due to extreme vibrations...
     
  5. BarelyAWake

    BarelyAWake New Member

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    While I'll agree on the weakness of the cheesy rims, aluminum bikes - even wallyworld ones can be fine for motorizing. The key is to use a careful eye when picking out the bike to be motorized while remembering that motorizing it will put far more stress on the frame than it was initially designed for - which is equally as true for steel as any other material.

    As an example I suspect any featherweight road bike would get shredded around here regardless of composition were it subject to a sustained 30mph with our roads, even without an engine lol, whereas my gusseted aluminum motorized mountain bike shows no signs of damage or fatigue after over 5000 miles of outright abuse despite the fact it's a wallyworld bike...

    It's just not the cheapest one they sell & it was chosen specifically for it's beefy yet lightweight frame ;)
     
  6. charles.paskell

    charles.paskell New Member

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    I have a steel frame i like it cause steel will bend under a lot of pressure and aluminum will just snap under pressure Id rather bend something than snapping it(causing catastrophic failure) I guess to each there own .
     
  7. Happy Jack

    Happy Jack New Member

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    Aluminum versus Steel (alloys) frames on a motorbike?

    IMHO : They are both practically equal in basic material pros and cons for the average bicycle.

    I have seen many changes over the years in bicycle frames.
    The basic Al versus Fe (Chromoly included) debate still boils down to the effect on the bikes overall weight, and overall frame strength per weight.

    More important than a bike being Aluminum or Ferrous Alloy (aka steels) is the joinery, the geometry, the metal gauge thickness.

    In other words, it is how good the "welds" or joining of the tubes are {butting-epoxying, gauge thickness, etc}; and how well those tubes are designed to work as intended on the bike.
    The Aluminum's can match or better the specs needed for your MB ride because of the old "power to weight" thing about pedaling (or motoring).
    BUT the design FASHION in bike makers seem to make a bike on what the public thinks they need. Currently lightweight aluminum for Dick and Jane riders is the flavor that balances manufacturing cost, and what the Maomart shoppers will pay. Rust prone steels fall out of favor, Cromoly has a price that is often above aluminum to manufacture.

    My vote is not on the material, but how it is put together, and how well it is designed to do the job.

    I currently rig an electrified cross-bike, I watch the welds every time I ride cause that is where I think I need to check.

    Summary: for most average bikes, my opinion is too LQQK closely at the joints/welds, look at the frames overall geometry (tube placements, thickness), see how the bike maker thinks that frames -front forks-rear bars are planned to work while you ride.

    For instance: some of you know , but others may be entertained to know: that a girls bike frame is historically weaker than the frame on a mans bike. Easier to swing a skirt thru that open area, but weak basic "U" design compared to the mens' historical diamond shape. BUT that was way back when womenfolk's were normally lighter in weight than the males.
    But then again? http://piratesofthecaribbean.me/images/fat_bottomed_girls.jpg
     
    #27 Happy Jack, May 27, 2010
    Last edited: Jun 7, 2010
  8. kicking

    kicking New Member

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  9. Kiwegapawa

    Kiwegapawa New Member

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    ... Ok, so here comes a dump question.. 1st, I understand the point of the out of round structual qualities of Aluminum vs steel compressing down on it with a different shape. But as in the picture of the nieghbor who knocked the structual integrity out of his frame [below]. These two reinforced female threaded holes shown in the picture. I'll bet just like my 4300 Trek, it has two more reinforced female threaded holes in the seat tube relevantly level with the first two shown in the picrure.

    ... Wouldn't it be a more structually sound to use these 4 point to create the fore and aft motor mounts? To add to this wouldn't it also be advantagous to create these front and rear mounts as a rubber sandwich both in fore and aft to subdue vibration problems? scratg

    ... There is no reason why Aluminum can't be structually sound. The lightest of these materials we trust all the time to makes our longest points in travel. As these mountain bikes we are speaking of are indeed created in aircraft aluminum. I would even further go to ask how thick is this point of reinforced female threaded holes? Enough so to say, tap out a larger size threaded hole? Without loosing integrity?

    ... Just things that keep poping in there of passing thought's. These while scanning through Stock Drive Products-Sterling Instrument in attempting to find a high quality formulation of the point.

    [​IMG]
     
  10. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    OK, just to shed a little light on the reinforced threaded holes, on an aluminum frame, those are threaded inserts that are installed with a tool that fastens them to the frame just like a pop rivet in effect. They are not reinforced at all and unless installed with a dab of epoxy tend too loosen up over time and eventually fall out. Then you can reinstall another one in its place usually.

    On steel and chromoly frames they are usually brazed-on little threaded lugs, quite a bit sturdier but for all intents and purposes just installed for carrying a water bottle and not much more.

    And a little side note on titanium frames, they are the frames you want too pay special attention for cracks and frame failure as titanium is very hard and brittle.

    Any frame can crack or break but I've witnessed more Ti frames break, than all the others put together. Doesn't stop me from loving Ti frames :D

    dnut

     
  11. 42blue15

    42blue15 New Member

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    Aluminum bicycle frames are almost always greatly stiffer than steel. They need to be, because aluminum suffers fatigue (stress cracking from repeated bending) much easier than steel does. This is why aluminum bike frames almost always have fatter tubes than steel bike frames do.
    ,,,,,,
    The problem with overloading or modifying a bike frame made of aluminum is that aluminum alloys owe a lot of their stiffness to the final heat-treating applied, where they are heated up to ~1000F and then cooled very slowly in an oven. If an aluminum frame cracks, the heat involved in brazing or welding it (with any welding method you use) is hot enough to also ruin the heat-treating around the repaired area, making it even less stiff than before. So to fix any aluminum bicycle frame, you need to weld it up, and then have the whole frame re-heat-treated. There's no other way to do it right.



    Steel (non-stainless) is the better choice if you want to modify the frame, build a frame from scratch or want to fix it yourself if it cracks. The fatigue resistance is higher than aluminum. It can be brass-brazed with a cheap MAPP/propylene torch. The names "mild steel", "hi-tensile" and "cro-mo" don't really mean much since they don't tell you the particular alloy. Mild steel is cheap but is softer than typical structural-grade steels.
    ,,,,,,,
    If you are buying steel tubing for a bike frame (in the USA) and don't know what kind of steel to get, ask for 4130 steel. This will be thin-wall, extruded, seamless, "cromoly", structural-grade tubing that works well with all welding methods. It's what you want.


    If you ever happen to find a stainless-steel bicycle frame (one that is unpainted yet has no rust, and that a magnet sticks to at least a little bit) don't do anything to it until you identify it. Don't even rub it with steel wool or scotchbrite to "clean" it, because you can scuff the surface finish that way. Stainless-steel bicycle frames from ANY time period are rare and pretty much all of them are collectible,,,,, $$$.



    Titanium is nifty and all, but it costs about 10X what typical steel or aluminum does and it must be TIG welded. As far as bicycles go--titanium parts are light, but also very flexy in use. Titanium has a very high fatigue resistance, and so to make the parts lighter, they are made very thin on purpose to save weight.
     
  12. Kiwegapawa

    Kiwegapawa New Member

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    ... Thank you for the heads up. I have a Trek 4300, it has Alpha Superlight Aluminum Frame. As Trek calls it. I was thinking about buying another to motorize. Wasn't sure at all before I asked. But now that I have a better picture of the materal aluminum. I'm going to pass. Heli Arc isn't cheap, Let alone getting into retempering the Aluminum. And as far as the 3/16" X 9/16" thread holes I spoke of, there is no way you can. As it is, it appears to me now, these riveted in place theaded holes, are a weak spot in the structure of the aluminum. I've used electric Arc and brazed many years. Only ever watched someone else with Tig err Heli Arc.

    ... Steel it is ~~~
    .weld
     
  13. happyvalley

    happyvalley New Member

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    Steel is real but aluminum is light and can be used effectively if you are not bolting into or clamping directly onto tubes. I've had good luck with some rack mounts.
     
  14. Kiwegapawa

    Kiwegapawa New Member

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    ... Though the point of Aluminum is light, which is great for those like myself that make it into the mountains and rough terrian. But the balance in these situations is indeed key in these highly active charges across these terrians. But like myself for those who have a high amount of experience and rode both materials, know of the point of rear wheel shift. Where and when the rear tire becomes air borne and shifts to the right or left. Sometimes even when heavily pumping on a flat surface in a hard drive. The bounce of the rear tire can do the same again here. At these moments the rider knows he's top heavy with the balance of the bike. The rider can feel and self balance easily to bring the rear wheel back down to the ground.

    ... This getting into a personal preference. I don't believe I wish to experience this shift, with an additional 20 lbs up over the rear wheel. This additional wieght over the rear wheel cutting into the correction time and muscling the shift needed to correct from this left or right shift. But here in why I am looking towards the more traditonal balanced placement of the motor.

    ... I've rode steel frame 30 years, up till 2003 when I bought my first Trek 4300. The difference in riding between the two are quite noticable. That 4300 was stolen. But enjoying the quality of the Trek had me immediately replacing it with another 4300 in 2006. My expectations of what I would be able to accomplish and maintain by motorizing one has become deminished. Steel will leave me with many more options in what the future could deal my way. Plus, I don't want to loose the point of being out there mingling with the spirits of the wild.
     
  15. happyvalley

    happyvalley New Member

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    That's a bit heavy for what I use and keep the weight between 12 and 14 lbs max. 6 lbs probably wouldn't be a lot of weight to many but you sound like someone who can recognize that difference. For me, how the bike handles ultimately has a lot to do with it's overall weight and so I'm also working to keep that under 50 lbs. Of the 6 MBs I have only 2 are aluminum but full suspension and the rack weight seems to get nicely balanced against the weight of the front forks.

    Overall I agree though, steel is real lol, and love the old Stumpjumper, Bridgestone MB1 and Dback Ridge Runner I have.
     
  16. Son of the sirens

    Son of the sirens New Member

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    Stolen? That sucks. My record for stolen was just 15 minutes after building it. Welcome to miami
     
  17. kevinkrg6

    kevinkrg6 New Member

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    It's obvious. Bamboo.
    [​IMG]
     

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