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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 4:24 pm 
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I particularly like the brake rotor seating....

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 5:24 pm 
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Now here's something that needs explanation. The only thing I can grasp is that it might be a hydraulic system like one might find on various Impala Low-Riders? Anyways it has to have some interesting trail issues with the axle moved so far forward.

Image

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 6:56 pm 
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I expect hidden springs inside those black tubes behind the forks. I have no real reason for suspecting something resembling an attempt at practicality; I just want there to be some kind of effort.... :(

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 7:17 pm 
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Duke wrote:
I have no real reason for suspecting something resembling an attempt at practicality; I just want there to be some kind of effort.... :(


That's exactly why my engineer brain can't understand why so many wildly impractical customized bikes could ever be considered "cool" looking by anybody. I can't get by the fact that it is obviously a horrible motorcycle that can't be ridden , no matter how much misguided work went into it.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 7:30 pm 
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What does your engineer's mind say about those caliper mounts that appear to be mounted so as to pivot freely on the axle? :lol:

Fortunately, the sort of person who owns such a bike is likely to be the sort of person who cautions others to "watch out; the front brake will kill you."

Of course, in the case, going from appearances, he'd be right! :shock:

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 8:12 pm 
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Well there does appear to be some kind of skinny rod strut running from the fork stanchion to the top of that caliper that would tend to hold the caliper back if you actually applied that brake. Even a complete moron would have figured out the caliper couldn't be free to just rotate on the axle.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 9:19 pm 
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In the interest of visual clarity, I took the liberty of zooming in, as it were...
Image

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 9:44 pm 
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Thanks. I missed that in the first look. Granted, I'm getting record levels of no-sleep this week. Blood pressure won't get low enough for me actually _relax_ enough to sleep. At any rate, I totally failed to see that linkage there.

Why would it need to be adjustable?

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 10:16 pm 
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I see three holes in the bottom end of the boomerang shaped lever that connects to the axle. Is that adjustment needed to allow the piece that bolts between the bottom end of the black rod behind the fork and the three holes?

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 10:30 pm 
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My guess is that it was part of a shifter linkage in another life.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Wed Mar 23, 2016 11:14 pm 
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Duckster wrote:
My guess is that it was part of a shifter linkage in another life.



That too

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 8:16 am 
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Looking at that bellcrank mechanism with the pinned horizontal tension member attaching to that black thing behind the fork leg, I'm thinking the black thing might be a leaf spring bolted solid to the fork leg at the top. That would account for all the pivot points in the linkage (and with no shock absorber,a lot of sloppy lost motion I'm sure) as well as the apparent curvature of the black thing.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 8:29 am 
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Fridgitator wrote:
I see three holes in the bottom end of the boomerang shaped lever that connects to the axle. Is that adjustment needed to allow the piece that bolts between the bottom end of the black rod behind the fork and the three holes?


I'd guess those are just "lightening" holes... Like weight matters on that POS.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 1:01 pm 
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Fridgitator wrote:
In the interest of visual clarity, I took the liberty of zooming in, as it were...


I fiddled with the brightness & contrast of that zoomed in pic:

Image

It's definitely a cable or line of some sort, it looks like a tension cable like you might find on a front drum brake.

One other question remains, beyond what the hell it actually is...note how the brake line is routed inside the former fork tube (with a questionable bend/bind to it at that) but this cable/line has been routed outside via clamps welded to said tube. "Dude, I cleaned up the front end by (partially) hiding the brake line and then added this (whatever the hell it is) cable on the outside!"

Also, did anyone else notice the headlight is nearly parallel to the forks?

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Dismantling, sawzalling, and rattle canning does not make a bobber. That's called an "ANCHOR".
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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 1:33 pm 
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I suppose there COULD be a right angle junction inside the fork tube for that brake line? Or does the brake line actually pass behind the fork tube and swing up toward the headlamp? I think I'm seeing some brake line to the right of the fork tube further up, and sweeping upward in a fairly gentle arc.
god, how did I get caught up in this?

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 1:36 pm 
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If the brake stay is in fact a cable rather than a linkage type rod, then I would hate to try to use the front brake to hold this pig from rolling backwards on a hill for example. the first law of Mechanical Engineering holds that you can't push a rope.

The torturous routing of the brake lines could have been made much easier by using a conventional banjo fitting on the caliper so the brake line attaches at right angles to the caliper rather than straight on. However, the large range of motion (fore and aft) of this type of suspension arrangement makes a big brake line loop essential to allow the suspension movement. The potential chafing at the fork leg attachment would definitely be a concern though.

Your photoshop work clearly shows the leaf springs behind the fork legs.
I did notice the cross eyed headlight, but figured the actual function of the light is probably not nearly as important as how it looks to the guy that built it.

"Dude, If you want to see a clean front end, check out the bike parked beside you. :D "

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 4:34 pm 
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Well I'll be...there is a leaf spring there. All this time I thought that was the front rim and was focusing on the cable.

Funny thing, this appears light years ahead of that Gold Wing chopper front end as far as utilizing hydraulic fork tubes would be concerned.

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Dismantling, sawzalling, and rattle canning does not make a bobber. That's called an "ANCHOR".
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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 6:39 pm 
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I see cable behind the fork. I'm almost certain that is a rod between the fork and brake, quite similar to the one found in a Rebel shift assembly. Something else I observed is that the way that thing works, when you hit a bump the axle moves up and slightly aft. With the rigid rod there, the brake caliper would have to rotate slightly counterclockwise relative to the fork. No problem if the front brake is not applied at the same time. If you apply the brake hard while the spring is being flexed, you would stop the up and down motion of the axle. When you release the brake, the front is going to hop like a flea.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 7:25 pm 
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Your analysis of the motion of the suspension and caliper on hitting a bump is correct, but the brake setup would not lock the suspension in place. First off, just applying the brake would tend to rotate the bellcrank (boomerang thing) clockwise lifting the axle up and backwards. Think of the brakepad/caliper being pinned solid to the disk as the wheel is turning. The caliper is prevented from moving fore and aft by the rod, so the wheel/axle assembly will now try to rotate about the caliper, lifting the axle up and back. A bump would add to this effect by pushing the axle up and back more.
Of course weight transfer to the wheel under braking would be a third contributer to front end dive in this scenario.
Releasing the brake would release the brake force and spring tension as you note, allowing the axle to spring back down and forward and without shocks, you could get some serious wallow happening.

A much better design would have been to anchor the caliper to the bellcrank arm, not the fork. This moves the free pivot point from the axle to the bellcrank pivot and would tend to rotate the bellcrank counterclockwise moving the axle forward and down. This would counteract the weight transfer effect resulting in much less dive under braking.

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 Post subject: Re: Craigslist SNAFU
PostPosted: Thu Mar 24, 2016 8:01 pm 
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I Love this sort of thing-- learning on the fly by listening to people who know what they're talking about. :)

I'm glad you guys are here. From my own perspective of relative ignorance, all I could think was "it looks like he took the rockers off his tandem axle utility trailer and thought "Hey, Bubba! I got me a _coool_ idea!"

;)

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