You're doing what? That must be dumbest thing ever.

[Spankyfart]

Right, so here goes.

I've got a few bikes, and then my g/f has a few. So that's almost a million bikes and I don't have the room.
I've been looking for a steel GT frame in my size since 1978 so that's not going to happen anytime soon.
What I do have is these bikes, and the GT frame was to be rebuild with the Cannondale bits.



Now the Koga is Carbon, it's 33 year old carbon at that.
While I am currently building it up with XT bits (they came in full DX) it is a bike I'm keeping.

I understand it's sacrilege, so I understand your anger and sadness but has all the things I want in an ebike conversion.
Has all the eyelets and screw in bits on the front and the rear end, it will fit a QR Rohloff which I'm getting in month and is in the height I need.

I have the white Magura's that will be mounted upside down on the U-Brake, I'll have bosses made exactly for them although I have enough spare Magura bit's to DIY it myself e.g. file of some of the mounting brackets.
That all isn't the hard part.




What might be a good question to ask, will this frame hold all the up and down, left and right torque from the Tongsheng motor.
It is a "normal" 25km/h motor but I disabled the limiter, on the Cannondale I do about 30-35km/h with it nothing crazy.
And most of the time slower as I ain't in a rush to get anywhere quick.
I'm not going to ride it as a mountain bike through the mud and up and down unpaved hills, it's just for transport.

Will this frame be tested in a way that it is going to fail miserably?
The consensus on the mighty interwebz where everything is true seems to say so.
What are your thoughts, dumbest thing ever?

 

[Guinessisgoodforyou]

No idea mate, ride it like you stole it and enjoy. Cool bikes.

 

[Spankyfart]

Yes Sir, but I won't find another Carbolite in this state.
Then again, they are "just" bikes. Or are they? Hmm..

 

[grantoury]

Those old Kogas were pretty solid builds, I think the carbon was reinforced with aluminium if I am not mistaken. Not silly light, right? Also, it is a Koga so well made. And you have decent brakes...

 

[Spankyfart]

 

[hamster]

I think the bit to consider is where the motor torque forces are applied. If any are to the middle of a tube then think about how to spread loads. Otherwise I wouldn't worry too much. 100kg of rider hoofing down on a stationary 175mm crank through a 22T chainring to a 34T rear is the largest torque load. It's something like 300kgf / 3000N of tension in the chain. No wonder chainstays flex!

 

[Spankyfart]

This is from my Carbolite 700C frame specs, they tubes are called Carbolite - 4.
The ones from the MTB are Carbolite - 3 tubing.
I might be able to find out it if they are the same, they were both built in '91 so it makes sense the tubes are "the same"

I wouldn't worry too much. 100kg of rider hoofing down on a stationary 175mm crank through a 22T chainring to a 34T rear is the largest torque load. It's something like 300kgf / 3000N of tension in the chain. No wonder chainstays flex!

I'm as dumb as they come when mathematics are involved, other then that I'm a pretty clever lad is there a way to calculate this and what do we need.
Tensile /torque strength of the carbon tubes? I'd have no idea where to get that.
I guess it's just a question of do it and find out?
As @grantoury said, it's not "just" carbon (see picture above).

hmm.. ponders..

 

[Ren Rawbor]

What exactly IS your size? Those frames look fairly lofty & I might have just the steel GT frame for you, if you're happy to cover postage/packing?

It's a lowly 96-ish Palomar, but it is (I think) about a 22" frame, can measure if you're interested & being a lower end frame no big deal for the puritans if it becomes an E-hack.

But yeh, as above they're your bikes to do with as you wish

 

[Spankyfart]

I'm 190, so anything from 58-61, that Cannondale is an XL so it's 56cm.
The Koga you see in the picture is a 57cm, but it has a really tall headtube so it rides differently and makes up for the height.
How that works, I just ride them but smarter people then me can explain that.

A real 22" measured GT would be too big, and I do have a few wishes when it comes to the frames (read - models)
So I'll pass and thank you for your offer but it needs to be specific frames for reason only scholars can fathom.
I'm a dude, I think I know what I want and then set my mind to it. Weird how that works.

 

[Ren Rawbor]

Just nipped out and measured said frame, it's 22 1/2" C to C and a whopping 24" Centre to top so effectively 61cm!

No problem, just thought I'd offer it up as I knew we saved it from the tip for something... Maybe one day the BFG will need a new bike lol