mjbalogh's Chopper/Bobber '81 GS750LX

[Ironriot]

Another quality with aluminum that would probably deter someone from building a frame of it is that aluminum, unlike steel, has a finite number of vibrations/bends in its lifespan before it breaks. Now that may be in the billions in certain situations, but it would really suck to suddenly have your frame snap under you should you hit a good jolter on a rigid frame like a chopper/bobber generally has.

Brutal ok this I DIDN'T know. Yeah this would be a deal breaker for me

As for the titanium frame that would be badass as hell. I wouldn't know where to begin working with it though. And isn't titanium brittle? Where as steel and aluminum have a good amount of give and bend before they break

[TheCafeKid]

I dunno...i think (and this is total guess) titanium is definately LIGHTER than steel and possibly more maleable (sp?) but probably doesnt have the tinsile strength of steel. not sure tho im no metalurgist.

[Ironriot]

Titanium is lighter and in fact is supposed to be stronger or atleast as strong AS steel but I remember reading that it had properties like cast iron where when it is put under enough pressure it would break instead of bending like steel does. which brings us right back to the frame snapping. but i'm no metalurgist either maybe there are different alloys of titanium nowadays my information is a few years dated

[Commodus]

Typical titanium alloys are actually heavier than steel, but they are much much stronger - so you can use much less material and thus end up with a lighter construct.

Ti alloys can also be quite flexy so they are an excellent materal for frame construction, especially in a rigid configuration. Lots of high-end bicycles are ti. Well OK not lots but it's not uncommon.

[Mark M]

Typical titanium alloys are actually heavier than steel, but they are much much stronger - so you can use much less material and thus end up with a lighter construct.

Ti alloys can also be quite flexy so they are an excellent materal for frame construction, especially in a rigid configuration. Lots of high-end bicycles are ti. Well OK not lots but it's not uncommon.

Ti alloys weigh about 60% of steel, have very high strength and no fatigue endurance limits. Ti is also about 60% as stiff as steel, so it will give more deflection for the same load. This does lend it to bicycle frames and it is an excellent material for that purpose. Pure Ti is not that useful, but a number of alloys are around that give good toughness, strength and workability.

Just for the record, steel also has endurance limits the same as aluminum, but they are harder to find and steel is generally more forgiving in it's failure modes. Aluminum can cause issues with cracking, especially due to engine vibrations.

Our frames are almost never that highly stressed, they are designed with rigidity as the main criteria and almost any frame that is stiff enough is also more than strong enough for typical operational loads. Crashing is not included in typical loads, however. And local cracking issues around engine mounts and such can be a real headache for all frame types, regardless of how strong they may be overall.

Mark

[TheCafeKid]

Nice! We have a metalugist here to teach us the ways of the force!!! And i just realized, and appologise for the fact, but we totally jacked this thread with our talk of metals and what not...Sorry man

[Mark M]

Nice! We have a metalugist here to teach us the ways of the force!!! And i just realized, and appologise for the fact, but we totally jacked this thread with our talk of metals and what not...Sorry man

Actually, mechanical engineer. But I have spent enough time pondering cool bike stuff at work that I have come across lots of useful info.

I noticed the hijacking in progress, but I figured it was semi on topic since we were discussing frame mods and changes.

Back to the cool GS of the original post,
Mark

[klhilberg]

I yuo decide to go full rigid with your fram you should check out Black Widow Choppers. They will take your frame and do the rigid conversion for a pretty fair price. My buddy sent them his Yam XS650 frame and they did it for less than 300 buck with a 3inch stretch. The rigid conversion gave it about 35 degrees of rake w/o changing the neck.

[mjbalogh]

No worries about the thread derailment. It was still related to the thread, and I learned some new stuff. Always cool. Please, keep it up guys.

I've looked at Black Widow Choppers before. ~$300 to hard-tail the frame isn't a bad price at all. I just have a hard time handing things off that I used to do myself.

ETA: As far as progress goes, I've had some new parts come in. Nothing major, and not the tank that I have been waiting on for a week already. It's getting to the point where I'm just going to spot weld or braise the holes in the existing tank just so I can get the bike on the road before the snow falls. Plans for this weekend include fabbing the seat mounts, and a mounting bracket for the tail light to turn the existing light/plate combo into a side-mount. If everything works out, I'll post updated pics.

[Commodus]

Ti alloys weigh about 60% of steel, have very high strength and no fatigue endurance limits. Ti is also about 60% as stiff as steel, so it will give more deflection for the same load. This does lend it to bicycle frames and it is an excellent material for that purpose. Pure Ti is not that useful, but a number of alloys are around that give good toughness, strength and workability.

Just for the record, steel also has endurance limits the same as aluminum, but they are harder to find and steel is generally more forgiving in it's failure modes. Aluminum can cause issues with cracking, especially due to engine vibrations.

Our frames are almost never that highly stressed, they are designed with rigidity as the main criteria and almost any frame that is stiff enough is also more than strong enough for typical operational loads. Crashing is not included in typical loads, however. And local cracking issues around engine mounts and such can be a real headache for all frame types, regardless of how strong they may be overall.

Mark

Learning is good

Thank you.

[Zooks]

All of the bikes in the pics are ridden by myself or family during our weekend rides, so it would be a bad idea for one to find a new home. Sorry.

Dude, that's a lot of bikes. Are you a member of the Partridge Family??

LOL

PS: I am surprised that no one has mentioned chrome-moly. It is the perfect material for making frames isn't it?? I was always lead to believe that it was super strong and had a higher corrosion resistance than steel (due to the chrome content). They make sprintcar chassis' out if it and NASA uses it in the framework of various projects.

[Mark M]

PS: I am surprised that no one has mentioned chrome-moly. It is the perfect material for making frames isn't it?? I was always lead to believe that it was super strong and had a higher corrosion resistance than steel (due to the chrome content). They make sprintcar chassis' out if it and NASA uses it in the framework of various projects.

It is suitable, but no really no improvement over mild steel because our frames are designed for stiffness and not strength. For off-road use, CrMo is better because it is more dent resistant due to the higher strength material. It is also more difficult to weld properly, more subsceptible to fatigue cracking , more sensitive to corrosion (generally, the higher the strength, the more corrosion becomes an issue) and much harder to bend.

On the plus side, you can usually build a lighter chassis with CrMo, but it will often have a limited life span as well. Lots of airframes have been made from it as well as chassis for many kinds of vehicles and it does work very well if you understand it's characteristics and use them appropriately.

Mark

[Mark M]

OK. I finally had some time to grab pics of the old girl. Keep in mind that she's still a major work in progress (and, let's be honest... she will be as long as I own her).

Michael

Any more pics or progress? I love the bobber look and I can't wait to see how it all turns out.

Mark

[PAULYBOY]

I just found this thread while doing a search for forward controls. Christmas day, my 20 year old and I took an old gs850 frame and , without having seen this thread at all, came up with this.

[ron bayless]

OK. I finally had some time to grab pics of the old girl. Keep in mind that she's still a major work in progress (and, let's be honest... she will be as long as I own her). I was working on stripping the tank, so there's some residue left (I wanted to see if it would be worth it to have the holes welded/braised). The tank, seat, and rear fender are just resting on the bike, and not in their final bolt-on positions and I need to finish bobbing the rear fender before I mount it.

But... without further adieu... pics:


Also, I've been doing some digging about the ceramic coatings, and I understand ceramic coating the pipes to trap and channel the heat, but I've also seen some of the spendier high-temp engine enamels that use ceramic to help release the heat. That said, I have a lot more digging before I finally sit down to tearing her all apart to coat/paint the engine and powdercoat the frame.

--
Michael

hAVENT BEEN TO THIS SITE FOR AWHILE.this is crusierlover.I only gave you minimal instructions for the forward controls.My effentosh crashed after i had written you a long detailed message.I will pm you more instructions if you still need them.I have a real computer now.Basically anyone can do the left shifter side, its the brake side thats the challenge.The old brake pedal can be hated and bent out and down enough to clear all the cases,just takes some patientce and a lot of heat.It looks like casted steel, but it isnt.That way you retain the splined coupler to fit over the splined brake shaft.Sorry about caps,had to unlock the key.my home email is crusierlover02@aol.com.Your bike is gonna be cool.I see Honda is coming out with a retro styled bike,if they sell,suzuki might do the same thing,but with their gixxers probably not.Gixxers as you know came from our gs engines.One of the coolest engines ever built and one of the easiest ones to work on.Ron B.