I need a Pro's Help

[Dn0rk]

http://www.re-cycle.com/ImageFetch.ashx?picNum=1&Size=2&ImageID=4289
Recently bought a 2 stroke kit from gasbikes.net, this is the bike i have to work with, can it be done?

 

[HeadSmess]

no.

well yes, it can... but dont say you werent warned when the seat stays break and the frame collapses at 45... mph or kmh , it still hurts


been there, done that

 

[Dn0rk]

no.

well yes, it can... but dont say you werent warned when the seat stays break and the frame collapses at 45... mph or kmh , it still hurts


been there, done that

umm... what seperates that problem from any other frame, its made of chromoly thats the best frame on the market bub

 

[HeadSmess]

look at the ends of the seat stays...if that is the exact bike youre planning on using.

youll note the ends arent butted up against (behind)the seat tube, but are merely brazed on either side... this places a shearing effect on the joint, a tensional force rather than a simple compression... then whack on a two stroke engine, that at 6grand produces a strong 200Hz vibration. this will result in failure. even just selecting a racer with lugged seat stays would gain my approval. these seat stays...dont!

even the strongest tig welded heat treated cro mo frame will snap when fatigued... an MTB is designed to take a fair beating before failing...a racer is designed to be light. minimal strength.

thats all as i said, been there done that, but if you think chicks dig scars...

yours sincerely, bub

 

[Dn0rk]

And to correct you the frame uses triple butting, research triple butting and you will learn that your frame is probably inferior to mine. sorry to correct ya, no hard feelings bub

 

[Dn0rk]

...

 

[HeadSmess]

oooooh, so inferior....

of course it was! it was a bleeding racer! much the same as yours except it was a porsche... and its not the only frame ive seen fail in this spot...

do you know what triple butting is? it has little bearing on JOINT STRENGTH. well, ok, it has some, cause a joint using the butted section wall thickness would fail hella quick. its thickened at the ends for a reason. dont go shooting your mouth off without really understanding what it means...

and, as i said, the seat stays on these frames are NOT reinforced, gusseted, lugged, socketed, whatever... no amount of butted tubing is going to cure that!

you will note that (if you look at the pic)...the TOP TUBE is socketed/lugged to the SEAT TUBE and STEERER TUBE. the DOWN tube is lugged to the STEERER TUBE and the BB. the SEAT TUBE is lugged to the BB. the CHAIN STAYS will be invariably lugged to the BB (cant see behind the crankset, but it is) but there the lugs end....


all you have to do is open your eyes.... look! use your head! that is the one critical joint! the seat tube to seat stays! and compare it to most other bike frames... i say most. not all. most.


i wouldnt open my trap if i didnt know about these things. you want a pros help yet cant take the advice they give you that is sensible, and based on practical experience, all im doing is saving you some future frustration and possibly hospitalisation, but if you want to act like a lil kid, go for it why ask for help if youre minds made up?

the easiest fix is to gusset the frame there(other than using another frame)... gee, if i hadnt thrown out that frame, a pic now would make all the difference...


yours forever and a day, bub

 

[GearNut]

With all due respect to you, DnOrk, most road bike frames are not in any way up to the task of dealing with the vibration, stresses and strains that a 2-stroke in frame engine kit puts them through.
While I cannot speak for everyone here, most all of us here are very safety conscious when it comes to flying down the road at 30 MPH or faster on a bicycle. Whenever possible we try to share our hard and sometimes painful lessons learned over the years when dealing with or recommending frame designs suitable to use.
Most road bike frames are very well suited to rack mounted friction drive kits or axle mounted chain drive kits. None the less one may find rather quickly that road bike tires are too skinny to provide well mannered handling when an engine is propelling you at speeds faster than most all road bikes naturally travel at.

Please re-consider your choice of bicycle. No one here wants you to get hurt.
Your may get lucky with that particular frame, but do you really want to find out how lucky or not at 30 plus MPH?

 

[Dn0rk]

Thanks,
I understand that it hasn't been done yet, but i do enjoy the skinny tires and the bike coasts like a dream, 3 pedals and im down the block. I'm an experienced rider, not saying that 30 mph isn't fast, but i believe i will be able to manage maneuverability. As far as the frame goes, its my understanding that the tubes are welded together first, then a sheet of metal is applied around the tube joint for extra support.
If i were to participate in a race on bikes, pedal driven or motor, i would choose the more agile shapes of a road bike, over a beach cruiser, since beach cruisers are sloppier for turning, and slight movements.
In all honesty do you really think the joint near the seat stays is going to shear? there is a 2 inch long sheet of metal on both the top and bottom of the top tube where it meats the joint. I think that should help. The fram also boasts a japanes lifetime warranty, not sure if its void after slapping an engine on though...

 

[motorpsycho]

just because a bike coasts fast doesn't mean that the frame will hold up top the vibrations of a 2 stroke strapped to it.
like it's been said before...race bikes are made to be light and agile, not for superior strength.

if you know how to set up wheel bearings, use the right grease and have perfectly trued rims you can make ANY bike coast fast. as soon as you bolt your rear sprocket onto that back rim, it will probably not be perfectly true anymore. I also would not trust those skinny tires at anything over 20 mph (just my opinion) even tho they are designed for racing.
i've been doing this motored bike thing for awhile now and i personally would not use a lugged frame to put a motor on.
those seat stays as headsmess mentioned, don't look very strong to me at all. in fact, the entire frame looks weak at every joint.
If it were me, i wouldn't use that frame for anything.
I'm not a fan of mountain bikes or cruisers (unless they are done up like a board track racer) because it seems like every time you see a motorized bike, that's the platform that the majority of people use.
if you've seen one, you've seen them all.
I can totally relate to you wanting to do something different than what everyone else is doing, but that frame is not the way to do it in my opinion.