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Old 10-25-2012, 02:00 AM   #1
Box'a'bits OP
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Is this a valid solution to some of our Paralever issues?

Discuss. Not mine, so I won't be offended

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Old 10-25-2012, 07:23 AM   #2
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Make it a heavy monolever. Nice. I'd have concerns about that weld pulling a chunk of the swingarm wall out the bottom as it definitely was not designed for that. How much that would help the u-joints, I don't think anybody can really say. I think the main problem facing those u-joints is that they don't run in an oil bath. That would solve all of it. Second, problem is the angles they're pushed to and this might reduce that a little bit. Overall though, I wouldn't do this to my own bike. I still think someone should try developing a sealed cv joint driveshaft for the paralever GSs. That application begs for a cv joint.
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Old 10-25-2012, 08:04 AM   #3
jackd
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+1 - I also don't think the sidewall of the swingarm is set up to take the loads that the welded bracket is now applying to it. Quite a bush league set up in my view.
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Old 10-25-2012, 08:38 AM   #4
naginalf
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Quote:
Originally Posted by Airhead Wrangler View Post
I still think someone should try developing a sealed cv joint driveshaft for the paralever GSs. That application begs for a cv joint.
That's not a bad idea! Not sure if anything is small enough, but perhaps something from a really small car. I'll take a look at the CVs from my buddies Tercel/Paseo. What's the diameter of the available space on either end, and what's the distance it takes to get to the smaller diameter of the shaft (and what's that too while we're there)? How much distance is there for the larger diameter before it starts getting smaller? Anyone have a paralever driveshaft apart?
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Old 10-25-2012, 08:41 AM   #5
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I have thought about doing that. This is probably been covered before, but the joint that usually fails ... is it the one connected to the final drive?

EDIT: Also ... you could add a longer tab to the swingarm so it would connect more of the swingarm ... but even then ... I'll bet the weight is not that bad ... it's aluminum.
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Old 10-25-2012, 08:59 AM   #6
Kai Ju
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It defeats the benefit of the paralever design, doesn't eliminate the U joints and likely weighs more than a monolever.
Why not just install a monolever swingarm ?
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Old 10-25-2012, 09:36 AM   #7
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Quote:
Originally Posted by naginalf View Post
That's not a bad idea! Not sure if anything is small enough, but perhaps something from a really small car. I'll take a look at the CVs from my buddies Tercel/Paseo. What's the diameter of the available space on either end, and what's the distance it takes to get to the smaller diameter of the shaft (and what's that too while we're there)? How much distance is there for the larger diameter before it starts getting smaller? Anyone have a paralever driveshaft apart?
I bet these guys could do it:

http://www.cvaxles.com/custom.htm
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Old 10-25-2012, 09:44 AM   #8
naginalf
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Quote:
Originally Posted by Airhead Wrangler View Post
I bet these guys could do it:

http://www.cvaxles.com/custom.htm
Oh hell yeah! 68.35mm is their smallest? I bet that would work. And if it costs less than the $550 it costs for the fully rebuildable upgraded shaft, which I suspect it probably does (or even if it is slightly more), this would be a great deal! I smell a group buy. Although, I remain fairly skeptical that we can get the enormous amount of space needed for a CV joint inside a paralever housing.
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Old 10-25-2012, 09:51 AM   #9
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Quote:
Originally Posted by naginalf View Post
Oh hell yeah! 68.35mm is their smallest? I bet that would work. And if it costs less than the $550 it costs for the fully rebuildable upgraded shaft, which I suspect it probably does (or even if it is slightly more), this would be a great deal! I smell a group buy. Although, I remain fairly skeptical that we can get the enormous amount of space needed for a CV joint inside a paralever housing.
The other cheap option to adapt would be an ATV CV axle. They're fairly small diameter and not very long. They're probably designed for similar torque too. A CV joint would handle sharper angles much better, run smoother also and might actually improve gas mileage a little bit.
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Old 10-25-2012, 09:56 AM   #10
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Quote:
Originally Posted by Kai Ju View Post
It defeats the benefit of the paralever design, doesn't eliminate the U joints and likely weighs more than a monolever. Why not just install a monolever swingarm ?
1. Becasue it's 4"longer than a Monolever.
2. Monolever rear ends with a spoke wheel are uber rare. They only exist for the ST and G/S bikes and you know how expensive those are.
3. Many people are turned off of BMW Paralever Airheads due to them being prone to shaft failure. If this little trick solves that problem ... Then the only weakness of the paralever bikes is solved.

Just my opinion of course.
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Old 10-25-2012, 09:59 AM   #11
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CV shafts wear and fail too .. typically about 95-125k miles for front wheel drive Honda, Nissan, etc.

as does any sealed bearings. after XX miles all bearings need maintenance. roller bearings that live in an oil bath gets continuous lube and typically will last life of vehicle.

this apply to all sorts of applications. for instance rear wheel bearings on a FJ-60 Landcruiser is bathed in oil and typically never need replacement.
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Old 10-25-2012, 10:17 AM   #12
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Quote:
Originally Posted by _cy_ View Post
CV shafts wear and fail too .. typically about 95-125k miles for front wheel drive Honda, Nissan, etc.
CV joints themselves can last a VERY long time if they remain well sealed. It's typically the boot that fails around 100k, letting in all manner of contamination and from that point on the CV joint eats itself quite quickly. No it's not something you could fix quickly and easily on the side of the road, but if it used two off-the-shelf CV joints from a common car then a repair could be as close as the nearest NAPA.
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Old 10-25-2012, 10:27 AM   #13
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Quote:
Originally Posted by _cy_ View Post
roller bearings that live in an oil bath gets continuous lube and typically will last life of vehicle.
You're right. The real solution would be an oil bath. The 1st gen paralevers were designed to run in an oil bath, but at some point immediately before release to the public they changed over to a dry swingarm. Plenty of publicity and sales photos of the bikes show drain and fill plugs on the swingarm. So does the parts fiche. The '88 and '89 paralevers still have the flat on the casting for the drain and fill plugs, but they never had the hole cut and threaded. It seems that the lower boot just wasn't up to the task for reliably keeping all that oil from dumping onto the rear wheel and represented too much of a liability.

Visible here:



...and here:



...and here (#15,16):



Here's an 88/89 with the flat visible on the swingarm casting:

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Airhead Wrangler screwed with this post 10-25-2012 at 10:35 AM
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Old 10-25-2012, 10:35 AM   #14
naginalf
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Quote:
Originally Posted by Airhead Wrangler View Post
CV joints themselves can last a VERY long time if they remain well sealed. It's typically the boot that fails around 100k, letting in all manner of contamination and from that point on the CV joint eats itself quite quickly. No it's not something you could fix quickly and easily on the side of the road, but if it used two off-the-shelf CV joints from a common car then a repair could be as close as the nearest NAPA.
I'm intrigued by this idea, but let's start a new thread about it, this doesn't really pertain to the OP.

In regards to the OP, aren't you reinventing the wheel a bit. You could achieve the exact same thing with less weight by cutting off the entire control arm bracket and installing two bolts through the top and bottom of the housings, which would also keep pressure off of the comparably weaker middle of the housing. Probably would need some sort of spacer to run parrallel to the shaft and go in between the two housings to prevent torsional force from ripping out the bolts, but that could work actually. Like someone else mentioned though, you'd be obfuscating the point of the paralever design that keeps the suspension from compressing under hard accelleration, but it worked for the mono and all the chain driven bikes in the world, so why not if you're so inclined.
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Old 10-25-2012, 02:11 PM   #15
bmwblake
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there was an airhead (oak i think) that had a prototype cv joint airhead driveshaft built for a gs years ago. i never heard the output of the testing but i gathered from a lack of feedback that it didn't go well.

my 88 and 94 swingarms both have the flat spot where the parts fiche shows the fill and drains for shaft oil.

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