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View Full Version : Juice Cafe - Time to trim the fat....or do we?



EVcycle
08 January 2011, 1355
Here is one for the Structural engineers...and everyone else too!

The frame looks to be extremely over engineered for this application.

The 250+ lb motor, 10 Lb Tank,etc is now being replaced by 100 Lbs of battery and motor.

Would it be that much of a stress issue if I removed the areas cut by the pretty purple lines? Most every motorcycle (cruiser) I have used including the Orange Juiced bike has a single
pipe down the center and not nearly the front support like this one has on the front.

http://www.elmoto.net/attachment.php?attachmentid=717&d=1294519332

http://www.elmoto.net/attachment.php?attachmentid=719&d=1294519335

http://www.elmoto.net/attachment.php?attachmentid=720&d=1294519337

http://www.elmoto.net/attachment.php?attachmentid=721&d=1294520023

teddillard
08 January 2011, 1401
Well, you know I'm no engineer, but I think you have to ask just how much weight you're trimming. If you're just removing two sections of tubing, about 24", of what looks like 1 1/2" steel, well, what does that weigh? Maybe 5lbs, I'm guessing? For that, I'm not sure it's worth it, from a weight standpoint. Maybe it's worth it from a space-to-fit-batteries perspective... From an aesthetic standpoint, well, that's another matter entirely. :D

EVcycle
08 January 2011, 1412
Hey Ted.

It is entirely for the space-to-fit-batteries perspective. It will not be seen as the Fiberglass tank/cover will hide it all.



:)

DaveAK
08 January 2011, 1602
If I were to do something like that I'd probably look at extra gusseting where the center tube meets the two outer tubes. I'd also feel that the diameter of the center tube might not be sufficient on it's own, and so maybe weld some angle top (and bottom if space allows).

Now I'm no engineer, so this is nothing more than gut feeling. And that feeling could actually be gas.

EVcycle
08 January 2011, 1624
Hey Dave,

I was thinking the same thing. Maybe even a piece of angle iron the full length
of the top bar to the back support where the seat/tank are mounted.

DaveAK
08 January 2011, 1639
Looking at it again it looks like straight tube, so if you could run a piece all the way down I can't see how it could hurt.

chdfarl
08 January 2011, 1835
Those tubes are there less for the weight of the bike as they are bracing the lower steering neck ( At least thats the way it looks to me ). Picture the stress at that point during braking and while leaned over. When the neck flexes to one side the stress travels down that tube to the rest of the frame and dissipates. That lessens the shaky feel. NO I'm not an engineer either!

ZoomSmith
08 January 2011, 2139
Once upon a time, I got a degree in Mechanical Engineering, not that it means anything since I've never designed a motorcycle frame.
I'm with Chdfarl & Ted on this. Without those pieces your steering head is going twist like a rubber band. It may not be catastrophic at surface street speeds, but it would make a pretty poor handling Cafe Racer.
Why risk it for saving a few pounds?

teddillard
09 January 2011, 0400
That's kind of what I was guessing, too. Here's my R5 frame, it seems like every frame I can remember seeing of that vintage and construction has those tubes and that triangular arrangement.

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1388.snc4/164041_1799470186042_1218396040_32104003_7932732_n .jpg

EVcycle
09 January 2011, 0719
Thank you everyone for the input.

A few more points to consider.
The bike will not be slinging around the weigh of the original motor.
There will be a "sub frame" added with the cross members of the battery supports.
This is not for weight savings, this is for battery clearance if I decide to add a 5th box of Lifpo4s.
Here is a look at the whole frame. With all the gusseting at the front, I would be am surprised anything would move.

http://www.elmoto.net/attachment.php?attachmentid=722&d=1294582003

Richard230
09 January 2011, 0817
If you cut those tubes I think you will have a folding motorcycle. I wouldn't do it unless you have a plan to replace them in some way. I am sure Honda didn't put those tubes there just for fun.

Square Wave
09 January 2011, 0944
Please don't. The shapes defined by those tubes are important. If you have to for clearance, you could replace them with tubes that bend around your intruding hardware, but even that is undesirable.

DaveAK
09 January 2011, 1207
I'm not so convinced it would be as disastrous as some might suggest, although personally I wouldn't take anything away without adding something back. It might be more hassle than it's worth, or it might be a challenge you can't resist. :)

EVcycle
09 January 2011, 1225
I'm not so convinced it would be as disastrous as some might suggest, although personally I wouldn't take anything away without adding something back. It might be more hassle than it's worth, or it might be a challenge you can't resist. :)

Most of the other cafe bikes I have had were single center post. I agree that it will require at least an addition of ...something if the other tubes are removed.
For testing purposes, I may do a cut single center cut of the two out side pipes, stick my race camera on it, do some maneuvers and see if there is any flex.
It can be easily re-welded if I do not like the results. That is the nice thing about a non ICE bike....no tank!!!


If nothing else, a triple wrap of duct tape around the center pipe should stiffen it up??? :O

chdfarl
09 January 2011, 1314
Why not cut out the middle tube then put two straight tubes to the ones you plan to cut. Then put a box where the tank went.

billmi
09 January 2011, 1315
If nothing else, a triple wrap of duct tape around the center pipe should stiffen it up??? :O

Not duct tape alone, but duct tape 3 or 4 chopsticks to it around the spot you're concerned with flexing, and you're good to go!

:-)

EVcycle
09 January 2011, 1335
Why not cut out the middle tube then put two straight tubes to the ones you plan to cut. Then put a box where the tank went.

An interesting idea. Measurements will be made once the fiberglass tank arrives. I will NOT be cutting anything unless I run out of options.

"Measure twice. Cut...if you have to" :)

EVcycle
09 January 2011, 1337
Not duct tape alone, but duct tape 3 or 4 chopsticks to it around the spot you're concerned with flexing, and you're good to go!

:-)

You are right, I forgot the chop sticks!!!!! :O