Topic: monoshock 750

[sander]

Hi all! I'm Sander from the Netherlands, new to this forums.

As my wheels were all wobbly, i thought i might as well put some modern wheels on my bike. Well you can guess the rest, plans got bigger and bigger...

So i bought myself this:
-cbr900 rearend (incl. monoshock)
-cbr900 wheels and brakes
-cbr1000 frontend (same inner bearing sizes, only a little longer stem)

A few pics of the new swingarm and shock..









Swingarm pivot bolt is 20mm so i had to make some new axleslots to fit the frame..



While i was at it, i made a new axle as well, because the cbr axle was to short for this frame..



Next thing to do will be mounting the forks and see how it fits..



Sander

[wannabridin]

looks good, but how will the vertical mounted shock perform?  seems like it would be a bit harsh and have the tendency to fold under a little bit, if that makes sense.  i know almost every mono shock bike i can think of has the shock mounted a bit on an angle with the top towards the front of the bike.  have you tested out the function of this?

now what are you going to do with the front suspension??

[sander]

Thanks!

On a stock cbr900 the shock is mounted this way. So it should work smooth. Also when compressing the shock, the bottom eye is rotating/shifting towards the rear due to the link system.

Front suspension is coming from a cbr1000f, but i still have to knock the old bearingcups out of the frame...

[andy750]

Very interesting and Ill be curious to see how this turns out.


Similar to this maybe?



cheers
Andy

[voxonda]

Dag Sander,

Leuk om nog een landgenoot hier tegen te komen, welkom!
So that's enough dutch for today.
Interesting approach, am collecting parts to build a 'old style' monoshock 750.

Cheers, Rob

[Alan F.]

Very nice, check out the link in my signature line for some related reading material.
-Alan

[Retro Rocket]

Hello Sander, nice project mate. can you tell me what the "new" wheel base will be, how much longer will it be.? Was the swingarm the same width or did you have to alter it to make it fit.? Cheers...Mick

[MJL]

I've been wanting to do a monoshock for awhile now, but there's not enough room for the airbox, battery, etc along with the monoshock mounted horizontally. I thought about an underbelly setup like Buell used to use, but then I'm limited to a Buell shock. What you've got there is a great solution, but I'm concerned about the amount of leverage and the spring rate needed. I'll be watching to see what you come up with.

[bert96]

 Where will you install the oil tank now



Bert

[sander]

Thanks for all the reply's!

Dag Sander,

Leuk om nog een landgenoot hier tegen te komen, welkom!
So that's enough dutch for today.
Interesting approach, am collecting parts to build a 'old style' monoshock 750.

Cheers, Rob

Hallo Rob! Ik ben benieuwd!

Very nice, check out the link in my signature line for some related reading material.
-Alan

I've read your topic, very interesting!

Very interesting and Ill be curious to see how this turns out.


Similar to this maybe?

...

cheers
Andy

No i'm going for a more "classic" look, stock tank, cafe seat.. Nice bike though!

Hello Sander, nice project mate. can you tell me what the "new" wheel base will be, how much longer will it be.? Was the swingarm the same width or did you have to alter it to make it fit.? Cheers...Mick

I don't know how much longer it is, i think about 4 inches. The swingarmpivot is 1 inch wider, so i cut and stretched the frame.

 Where will you install the oil tank now

Bert

The shock has an offset to the left so the stock oiltank still fits. Just barely but it will do..

Sander

[fastbroshi]

This should be relative to what you're doing.  Pretty cool animation of the Pro-link in action:

http://images.sportrider.com/bikes/2004/2004-honda-cb1000-upl.gif

The swingarm looks like one from yours, but from a different model judging by the title of the link.  However I'd be willing to bet the bike you got yours from didn't have a solid mount, rather it probably had a dogbone link of some sort allow movement of the top eye of the shock to move in a circular plane.

[nobody]

This might give you some ideas for how this should be done.



from this site
http://www.eurospares.com/newadd.htm

[Alan F.]

I'm not worthy!  I'm not worthy!

[Alan F.]

I would think that as long as the suspension geometry from the donor bike is kept, that all will be well and you can tune the suspension to the weight of the CB750 and the rider accordingly with different length dogbones and springs.

That TF pic is great, any more where that came from?
-Alan

[nobody]

I have no more info on it. The website just has pictures, sure is a pretty machine though.

[voxonda]

That is the one Tony Foale build, an that is the style I am after. Straight forward concept.

[fishhead]

This should be relative to what you're doing.  Pretty cool animation of the Pro-link in action:

http://images.sportrider.com/bikes/2004/2004-honda-cb1000-upl.gif

The swingarm looks like one from yours, but from a different model judging by the title of the link.  However I'd be willing to bet the bike you got yours from didn't have a solid mount, rather it probably had a dogbone link of some sort allow movement of the top eye of the shock to move in a circular plane.

 The 900 RR has the link that is shown on the CB 750 above. I was going to comment about the bottom frame mount being "solid", but if you look closely at the pics above, you'll see the suspension link inside the solid welded-on mount (Bolted to the front hole of the welded bottom mount on the frame and bolted to the bottom triangular bottom shock mount thing).
 The animation website link is for the later style CBR 600 style swing arm(and other CBR models). The later style swing (with the "floating top shock mount") would be nice for the CB 750 oil tank clearance issues that may arise with other monoshock mounts that would mount solid (simular to the 750 pictured above- although, this set up clears the oil tank).

 Looking good ,Sanders!

[voxonda]

On my (ex-)Martin framed 750 the oiltank was wrapped around the shock.


A lot is possible.

[bigsherm]

Here's a design I worked on.  It's based on the measurements of the '78 CB750 frame, with the stock swingarm braced and using a '90's Ducati 900/750SS shock.

This brought the top of the shock near a junction of the frame tubes that would provide good strength, very similar to the awesome Tony Foale monoshock bike.

I did my best to mock the Ducati geometry, and ensure a rising-rate compression of the shock.

The seat support subframe tubes were moved in the drawing, like Benjie's Cafe Racers likes to do, but that is cosmetic, and the rest of the frame geometry is modeled after technical drawings from Honda.

Sherm

[sander]

Thats a nice setup Rob! Do you have more pics of that bike?

The Tony Foale bike looks good, allthough i don't like the seat that much.

I have some pictures of the original 900RR shock. See if i can find them...

[sander]

Found them..





I came across some other inspiration pics.. this is the look i'm after

[sander]

I've got a little update on the bike...

I've replaced the bearings and put a spacer under the lower one to fit the forks in. The spacer is about half an inch.

[KB02]

Looking good.

That frame looks so wimpy compared to that swingarm. 

[fastbroshi]

Cool!  Looking good my friend.  Might as well add some gussets and one of Gordon's (I think) frame mods while you're at it.  Almost forgot to ask, is that a 16 or 17 inch front wheel?

[Toxic]

Looking good.

That frame looks so wimpy compared to that swingarm. 

I was just thinking the same thing.

I am looking forword to the completion of this project.