Topic: Getting ready to build a frame, opinions?

[tourmax]

I’ve just about collected up the steel I need to build a custom frame for my 82 cb650.

I’m back and forth on what type to build though.

The front end is off an RZV500, the swingarm/suspension is cbr600 and the front and rear wheels are from an r6.

I’m trying to decide between a perimeter trellis frame:



(Thats just a rough photochop)

Or a Moto Martin style frame:







Either one is within my wheelhouse to build, I’m just back and forth on which way to go. I’ve built frames before, but never a trellis frame, which is part of the reason I want to try one now. 

The Martin is “more or less” a proven design, my trellis frame will require more work and calculations.

The trellis looks to be “stiffer” than the Martin, but adding a little more triangulation to the Martin might compensate for that.

So, what do you think? Custom trellis perimeter frame or a Moto Martin “clone”? The Martin is also more or less a perimeter frame, its just not a full trellis from head to swingarm pivot.

This is just a street bike that will get the occasional spirited Sunday ride, so no class rules or such to worry about. I’m free to indulge my creative spirit as much as I want.

[RAFster122s]

Surprised no one bit on your invitation to venture a vote.

I personally would consider which one allows me to maintain and/or do the periodic or other maintenance without needing to have tiny hands which I do not.

You can always revisit it later if you build it with a trellis frame and then decide you want it with the Moto Martin designed frame… just means a new frame build… Yeah, I know, something you would rather not do…hack it up a second time.
What better way though to have a decision of being able to compare them to see which you liked would be to have both.

David

[MauiK3]

Ive never been a perimeter frame fan since most of the time it tends to hide the motor more. The Martin type seems to be more minimalist, might look better

[jgger]

I agree with MauiK3, I like the looks of the Martin.

[Don R]

  I like the Martin, I'd mimic something that is known to work well.

  (Old guy story alert)
    In our rear engine dragster, I paid for a shop to do a "pro"-built rear half chassis with 4 link suspension that lasted 2.5 seasons before chassis tube failure and required constant maintenance.  We cut that off and copied a well-known sportsman door car chassis design but made it narrower. Since then, it works great, we've had no repairs needed and it's been seven years. 

[Rick4004]

One frame design is not necessarily "stiffer" than the other, it comes down to details of the design. There is also different types of stiffness, for instance torsional, lateral, and braking stiffness.
In a broad view, the advantage of the trellis is a more direct connection of the steering head to the swingarm pivot. The advantage of the Martin style is the wide triangulation that can be achieved.
One suggestion, maybe rethink the CBR600RR swingarm. It is really long and works best with a short engine. You are likely to end up with a bit of a long wheelbase with that swingarm.

Rick Denoon

[david 750f]

I'm glad that Rick commented, check out his website.

http://www.denoonsp.com/frame-study.htm

[Don R]

 A friend built a few drag cars, his intention was make them as stiff as possible. He did fix many flex points but they didn't work as well as his old flexible chassis. When the light bulb lit up and he realized he overdid it, he took a sawzall and cut out a bunch of engine mount re-enforcing. The car worked well after that and they changed the design.

[MJL]

I've always liked the Martin frame.

[BomberMann650]

The martin style may work out better in the long run.

The cb's love top end maintenance - and the frame loops lend themselves to keeping stress off the old block.

[MauiK3]

What material would be used?