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Author Topic: Jared's 1982 CM450C Cafe Project  (Read 25243 times)

Offline cxman

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Re: Jared's 1982 CM450C Cafe Project
« Reply #10 on: Dec 11, 2013, 18:01:41 »
you are about to put a considerable twisting force onto a stamped sheet metal frame member

in order to support the single sided swing arm

the whole center section will need to be strengthened and re=enforced as well as i might suggest

solid butt welded as it is only spot welded together
1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline jaredc7

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Re: Jared's 1982 CM450C Cafe Project
« Reply #11 on: Dec 19, 2013, 18:49:23 »
Thank you CXMAN and 1969 Honda, both very good points! I am looking into a larger housing for the swing arm pivot rod (steel tube 15mm ID, and 3/16" wall), as well as strengthening the steel around that housing. I'm also having a friend do a stress analysis and engineering design on the rear shock top mount. Hoping to optimize that connection.

One thing I am having trouble with is my research on the front fork swap...

I've looked up the extensive list of front and rear axle diameters, steering stem bearings, etc. but cannot find bikes listed that are newer than 15 years old! I'm looking for a newer set of used forks that would work with VFR wheels (20mm diam axle). Are there any newer bikes that have a 20mm front axle diameter? If not, couldn't I just get bearings from AllBalls with the same ID (20mm) and a larger OD to accommodate the larger diameter axle size on the forks?

FYI... I assume to be pretty constrained to VFR wheels on my cafe rebuild because I am using the NT650 Hawk single swing arm and need the offset rear wheel. I would use the Hawk wheels but they look like crap. Also, from the research I've done, a conversion to Ducati or Triumph offset wheels seems far too involved. Maybe I'm mistaken about the ducati and triumph wheels?

Thanks!
Jared
Jared

1982 Honda CM450 C

Offline swan

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  • Kickstart, shift on right, drum brakes and spokes
    • 1962 BSA Gold Star barn find restoration
Re: Jared's 1982 CM450C Cafe Project
« Reply #12 on: Jan 03, 2014, 10:41:43 »

Goals for Cafe Rebuild
- Single swing arm conversion
- Monoshock conversion
- Old styling with modern performance parts

I'm already into a couple issues and expect some custom fabrication. I'm looking forward to hearing a variety of thoughts and ideas from this forum!

I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?
1966 Triton cafe, 1962 BSA Gold Star DBD34, and 1966 T120 Triumph Bonneville.
BSA Gold Star barn find restoration
1975 CB400F Cafe Racer build
1966 Triumph Bonnevile restoration

Offline Joon-yah

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Re: Jared's 1982 CM450C Cafe Project
« Reply #13 on: Jan 03, 2014, 10:52:53 »
I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?
   That'd take away all the fun!!
Cm400/cb450 http://www.dotheton.com/forum/index.php?topic=45376.0                                                  SR500 http://www.dotheton.com/forum/index.php?topic=43591.0                                                     http://retromoto1.com/

Offline jaredc7

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Re: Jared's 1982 CM450C Cafe Project
« Reply #14 on: Jan 08, 2014, 16:19:44 »
I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?

Stop looking at me swan!!! Sorry, I could resist... Billy Madison gets me every time!

The main reason I went with a motorcycle rebuild instead of just buying a used Ducati Monster is because I am a very handy Mechanical Engineer, and my job over the last few years is primarily focused in project management. While its a very good and engaging job, it severely lacks in providing an engineering outlet that I've always wanted. When I was younger it was taking things apart, plastic car models, erector sets, etc. Of course I am always tinkering and fixing my car, but there have never been any real engineering challenges lately. And while my engineering degree had an emphasis in motorsports engineering, the rebuild process for an old motorcycle is just fascinating for me. And cheaper than cars!

Basically, the reasons I'm doing a complicated cafe rebuild, like Joon-yah Bourelle so perfectly stated, is because its the challenge that drives me. And because I know that I can do it! My goal isn't exactly to have a pure riding machine, but rather "one-off" novelty-type machine that's more a labor of love than anything else. The fact that I will get to ride the motorcycle after its all done is just icing on the cake for me!

PS - here are a few sites with single-swing-arm cafe racers... they're awesome!

Honda CB - http://www.bikeexif.com/honda-cb-cafe-racer
Honda CX500 - http://cx500forum.com/forum/cx-customization-modifications/21309-cx500-very-special-single-sided-swing-arm.html
W650 - http://angelandthrills.blogspot.com/2011/10/w650-with-single-sided-swingarm.html
http://forums.sohc4.net/index.php?topic=85413.0
Jared

1982 Honda CM450 C

Offline jaredc7

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Re: Jared's 1982 CM450C Cafe Project
« Reply #15 on: Jan 31, 2014, 16:06:59 »
Here's a little progress on my cafe rebuild... The four pictures are from installing the new rear swing arm pivot housing... plus a little extra stiffeners   ;)

I do have one question right now... Before I start designing the rear shock top mount, I am double-checking all my suspension geometry. The one thing I am having trouble researching is the sprung mass to unsprung mass ratio. I have the dry and wet weights of my bike, the travel and spring rate of my 2013 Yamaha R6 rear shock (~4.5 inches and 547 lb/in).

But in order to get the right profile of the rear shock top mount pieces, I need to know where the rear shock will be. Basically, I'm trying to find the angle of my rear swing arm with no rider, with rider, and while driving (always dynamic, I realize). Once I nail down the rear swing arm angle, I'll be able to position the rear shock, and design/fab my rear chock top mount pieces.

Soo... Is the percentage of sprung mass about 75%? Maybe 80% That should get me pretty close. Unless some of you disagree, then I'm down to weigh individual pieces that are unsprung!
Jared

1982 Honda CM450 C

Offline xb33bsa

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Re: Jared's 1982 CM450C Cafe Project
« Reply #16 on: Jan 31, 2014, 16:45:39 »
why not just copy the aprox swinger angle of the nt650? then before final make sure you have good cornering clearance(50 degrees or so) with all front and rear suspension set to height an fully loaded as in a turn near full bump
how did you get that tube welded in straight? what kind of outboard frame tubes will you fab ? that center section is way to flexy to do the job on its own,unfortunatelly
I don't think you need to worry about antisquat too much that pertains to a bike that  has some horsepower

Offline cxman

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Re: Jared's 1982 CM450C Cafe Project
« Reply #17 on: Jan 31, 2014, 17:06:17 »
easier way to do the weight thing

place the rear tire of the bike on a scale

get on the bike and have someone help you balance take the weight down

set the bike on the center stand

disconnect the rear shock from the swing arm

let the wheel slowly go down on the scale take down weight

you no have rear max sprung and un sprung weight

1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline 1969Honda

  • Posts: 296
Re: Jared's 1982 CM450C Cafe Project
« Reply #18 on: Feb 01, 2014, 01:01:50 »
In regards to your fork/axle swap comments don't worry so much out the stem and axle diameters.  Measure out the bearing dimensions and then model up your own axle and stem.  I don't think it would take much for you to figure out a bearing size that is easily available on your rims and then machine a corresponding axle to fit the forks and wheel.  As for the stem, it's a actually pretty common to swap stems on the lower triple to get right combination of length and bearing size.  You might be limited on your budget to the VFR wheels, but bearing conversions aren't to expensive and turning a new stem or axle shouldn't be to bad either.  Also check out misumi-usa.com before you commit to a machinist on the axles, they have pretty competitive pricing for custom shafts with configurable machining options. 

On your VFR rear rim, don't be surprised if you have to make any spacers to push the wheel to the right to clear the swingarm as well.  IIRC correctly they are so much wider/offset differently than the NT650 you will need to add an 8mm spacer or so, surf around the build threads on customfighters.com, they've got tons of builds doing the SSSA conversions on sportbikes that you can pull applicable information from.

Keep up the good work and post lots of pics for those of us who enjoy the unusual/unconventional!
"Life happens, you'll either get over it or die from it"

Offline jaredc7

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Re: Jared's 1982 CM450C Cafe Project
« Reply #19 on: Feb 06, 2014, 16:49:49 »
why not just copy the aprox swinger angle of the nt650? then before final make sure you have good cornering clearance(50 degrees or so) with all front and rear suspension set to height an fully loaded as in a turn near full bump
how did you get that tube welded in straight? what kind of outboard frame tubes will you fab ? that center section is way to flexy to do the job on its own,unfortunatelly
I don't think you need to worry about antisquat too much that pertains to a bike that  has some horsepower

Thanks for the suggestion. I went the the Hawk 650 forum and got some info from one helpful person over there. I also stirred things up a little bit... seems there's quite a few people that are skeptical of this project! Hell, I don't blame them, the SSA and monoshock conversion is pretty alarming.
http://www.hawkgtforum.com/forum/forum/honda-hawk-gt-bros-discussions/mechanical-and-technical/639903-need-help-with-the-nt650-hawk-suspension-geometry

I had the tube welded in straight by referencing two other points on the same vertical section of the frame. The three points formed a triangle, so I got the centerline of my new tube to be the same distance on both sides from the two other points, I knew I was good.

For the outboard frame, are you talking about something that would connect to the outside of the SSA pivot like the Hawk frame does? I wasn't planning on adding anything to the outsides of the SSA, but that is a very goo point to consider, thank you.

I agree with your comment on the anti-squat, and I've gotten a similar reply from a few people in the Hawk 650 forum. It's more of an exercise in engineering that I'd like to solve rather than a practical problem that needs a solution. It is likely that my NEXT build project will need the anti-squat optimized!!
Jared

1982 Honda CM450 C