CHRIS_D
Well-known member
Hey OCfjr,
I can't find this part on Farklemaster's site? Would you have a link?
Thanks!
Frankenbike goes to the Darkside
- Thread starter RadioHowie
- Start date
Help Support Yamaha FJR Motorcycle Forum:
I can't find this part on Farklemaster's site? Would you have a link?
Thanks!
majicmaker
Well-known member
MC,Looking at wfooshee's animated GIF, it strikes me that if the torque arm is made single sided, even a "full width" one, when braking it will put a twisting moment on the mounting features at each end, instead of a simple pull. Might this lead to a stress fracture in time in the arm, the mounting lugs, or the bolts?...Animated GIF showing (about) the piece removed.
It's not that it's the ONLY way to stop the bike. If it breaks while you are using the rear brake, the calipers will be violently moved round with the disk until the hydraulic line splits. I'm not sure what will happen then, but I can conceive of it jamming the wheel if it gets round far enough to reach the swing arm.
An attempt to calculate the force on the torque arm under heavy braking :graduated: :
Let's say
Then
- The rear wheel radius is 15.25 inches,
- The effective brake disk radius is 5 inches,
- Weight of bike and rider 850 lbs,
- Assume a 1 G deceleration,
- The rear brake providing 10%.
That's three quarters of RH's whole weight (from what I hear
- Force on rear tyre is 10% of 850 = 85 lbs.
- Force on torque arm is 15.25/5 x 85 = 259 lbs.
).
Imagine (most of) RH dangling from this one-sided fixing, the pull being repeated many times on the one-sided attachment points.
OK, I'm paid at work to look for worst case scenarios. It'll never happen
On the first part of your quote, Yes, there will be a slight tendency for some Torsion (Twisting) Load applied to it. But, the Lug on the Swing Arm is strong and thick enough to handle it with no problem. The possiblilty of stress fracture is negligible. It doesn't have the Moment Arm or "Leverage" to do any damage.
On the second part, I'm paid at work to look at the worst case senerio also. I agree with you that it will never happen. No matter how much of Howie is Dangling!!
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RadioHowie
I Miss Beemerdons!
I don't see how there COULD be a twisting force applied to the torque arm, since the rear caliper can only move in a rotational axis parallel to the wheel. The caliper is solidly located on a horizontal axis by the axle, so there is no possibilty of the caliper to yaw, causing any twist on the torque arm.
I've edited your figures to more closely represent the bike's weight and mine combined. Benefit of the doubt, y'know.It's not that it's the ONLY way to stop the bike. If it breaks while you are using the rear brake, the calipers will be violently moved round with the disk until the hydraulic line splits. I'm not sure what will happen then, but I can conceive of it jamming the wheel if it gets round far enough to reach the swing arm.
An attempt to calculate the force on the torque arm under heavy braking :graduated: :
Let's say
Then
- The rear wheel radius is 15.25 inches,
- The effective brake disk radius is 5 inches,
- Weight of bike and rider 900 lbs,
- Assume a 1 G deceleration,
- The rear brake providing 10%.
That's three quarters of RH's whole weight (from what I hear
- Force on rear tyre is 10% of 900 = 90 lbs.
- Force on torque arm is 15.25/5 x 90 = 274.4 lbs.
Another edit to more closely mirror reality. :finger:
I agree. It'll never happen. Certainly, not for me. I rarely use the rear brake, and when I do, it's mostly as a "hill-holding" device when I'm stopped and want to give my right hand a rest, or when I'm trail-braking at parking lot speeds, such as U-turns, in preparation to park the bike.OK, I'm paid at work to look for worst case scenarios. It'll never happen
Again, I don't see how. The only force being applied to the brake caliper is a longitudinal force, parallel to the fore/aft centerline of the bike. The force is directly in line with the torque arm, which is also parallel to the centerline of the bike. How could there be any twisting force applied to the torque arm, unless the only moving part of the equation, the brake caliper, can yaw on a vertical axis to the axle? Even then, if the caliper could twist, it's clamping down on the disc rotor. The only way the disc rotor could cause the caliper to yaw in a vertical axis is if the rotor was severly warped. And the rider would notice and correct that LONG before the torque arm could be compromised.
I really think this torque arm issue is being over-analyzed.
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wfooshee
O, Woe is me!!
I think they're saying that the tabs at the end could be bent, as if you took a pair of pliers on a loose piece and bent the tab back and forth. I don't see it, and I agree the analysis is getting carried away.
That tab is in tension, but there's no flex on it that I can see.
That tab is in tension, but there's no flex on it that I can see.
The reason that the tabs would want to flex is because you will only be pulling on one side of the tab.
The pull from the tab on the brake caliper would be transferred to the small bolt and subsequently to the tab(s) on the strut link. With only a one sided link the bolt will want to **** laterally within the hole of the tab. Same thing at the other end in reverse. So yes, there will be some amount of torsional force on the tabs at each end.
Whether it is significant is another issue.
Clearly, the designer avoided that twisting force by having a two sided connection of the strut end to each tab. That way the pull is evenly distributed and there will be no twisting force on the bolt or the tab.
The pull from the tab on the brake caliper would be transferred to the small bolt and subsequently to the tab(s) on the strut link. With only a one sided link the bolt will want to **** laterally within the hole of the tab. Same thing at the other end in reverse. So yes, there will be some amount of torsional force on the tabs at each end.
Whether it is significant is another issue.
Clearly, the designer avoided that twisting force by having a two sided connection of the strut end to each tab. That way the pull is evenly distributed and there will be no twisting force on the bolt or the tab.
RadioHowie
I Miss Beemerdons!
I just KNEW if someone could describe a possibility it would be you. Makes sense. :thumbsup:
I'm thinking this could be an issue if the ends of the torque arm "floated" on the bolt, as in if the bolts tightend down on a shoulder, resulting in a virtual hinge at both ends of the torque arm, but the issue diminishes exponentially since the bolt head tightens down on the tab itself, essentially creating a one-piece connection between the calper and the swingarm. If the forward mounting point of the torque arm was attached to something other than the swingarm, then a hinge at both ends would be necessary, but since the both ends of thetorque arm moves in concert with the swingarm, a "solid" connection is created by bolting the arm solidly at both ends.
In reality, if the torque arm was welded to the swingarm at one and and the caliper at the other end, there wouldn't be any possibility of vertical flex at the attachment points. But it would make it a pain in the *** to get the caliper out of the way for a wheel change. That's the only reason the arm is removal to begin with....to simplify wheel changes.
Yes and no.
Since we tighten the bolt up snug it does limit the bolt from actually "cocking" inside the hole, but the same forces that would **** the bolt still exist, and those would still equate to a rotational force on the tab. In order for the tab to actually flex in that direction, the end of the strut link would also have to flex lengthwise, (since the two are bolted solidly together). Therefore, another way to help prevent the tab from flexing would be to ensure that the one sided strut link is made of a stiff enough material that it would not flex easily.
I don't really think that any of this is a big issue as the parts appear to be more than substantial enough for these forces. But it's hard to say for sure without performing destructive tests.
Since we tighten the bolt up snug it does limit the bolt from actually "cocking" inside the hole, but the same forces that would **** the bolt still exist, and those would still equate to a rotational force on the tab. In order for the tab to actually flex in that direction, the end of the strut link would also have to flex lengthwise, (since the two are bolted solidly together). Therefore, another way to help prevent the tab from flexing would be to ensure that the one sided strut link is made of a stiff enough material that it would not flex easily.
I don't really think that any of this is a big issue as the parts appear to be more than substantial enough for these forces. But it's hard to say for sure without performing destructive tests.
wfooshee
O, Woe is me!!
In the spirit of compleat over-analisys:
There is the factor to consider, that this is a sliding caliper. It is not fixed in its position, and as the pads wear the caliper moves to accomodate the pad wear. Therefore we can't count on the tension arm being exactly perpendicular to fastener bolts. The angle would be small, as the maximum horizontal displacement of the caliper is the thickness of one of the pads' wear material (the piston extends an amount equal to that displacement to absorb the other side's wear) but it would not be zero.
Secondly, the bar is not always in tension. RH hisownself mentions the fact that the rear brake is used for hill-holding when stopped on an uphill grade, and at times such as that, the bar is actually in compression! OMG, what now??!!!??!
Just thought I'd throw those out for fun.
There is the factor to consider, that this is a sliding caliper. It is not fixed in its position, and as the pads wear the caliper moves to accomodate the pad wear. Therefore we can't count on the tension arm being exactly perpendicular to fastener bolts. The angle would be small, as the maximum horizontal displacement of the caliper is the thickness of one of the pads' wear material (the piston extends an amount equal to that displacement to absorb the other side's wear) but it would not be zero.
Secondly, the bar is not always in tension. RH hisownself mentions the fact that the rear brake is used for hill-holding when stopped on an uphill grade, and at times such as that, the bar is actually in compression! OMG, what now??!!!??!
Just thought I'd throw those out for fun.
RadioHowie
I Miss Beemerdons!
....and to continue the spirit....In the spirit of compleat over-analisys:
There is the factor to consider, that this is a sliding caliper. It is not fixed in its position, and as the pads wear the caliper moves to accomodate the pad wear. Therefore we can't count on the tension arm being exactly perpendicular to fastener bolts. The angle would be small, as the maximum horizontal displacement of the caliper is the thickness of one of the pads' wear material (the piston extends an amount equal to that displacement to absorb the other side's wear) but it would not be zero.
Secondly, the bar is not always in tension. RH hisownself mentions the fact that the rear brake is used for hill-holding when stopped on an uphill grade, and at times such as that, the bar is actually in compression! OMG, what now??!!!??!
Just thought I'd throw those out for fun.
The rear brake IS a sliding caliper. No doubt. But it slides on the carrier hanging from the axle. The carrier itself does not have lateral movement on the axle, unless you leave out the spacer and washer, so there is no lateral torsion to the torque arm. The torque arm mount, B, is on the caliper carrier, not on the caliper, which slides on bolts A:
Gotta admit, though....you got me on the hill-hold facing uphill. In compression then, for sure.
wfooshee
O, Woe is me!!
Damn, you're right. I hate being caught wrong in public. Crap! Had I actually looked at the thing instead of imagining it in my head. . . . . .
I'll just add one more thing that I thought of. If the bar breaks, the caliper may roll around the axle and whack the swingarm, but it won't lock the wheel, because by the time it winds around that far it will have pulled the hydraulic line off, removing brake pressure.
So you're not gonna go splattering your ****-eating grin onto the asphalt because the bar broke.
Which I'm sure makes you feel gobs better.
I'll just add one more thing that I thought of. If the bar breaks, the caliper may roll around the axle and whack the swingarm, but it won't lock the wheel, because by the time it winds around that far it will have pulled the hydraulic line off, removing brake pressure.
So you're not gonna go splattering your ****-eating grin onto the asphalt because the bar broke.
Which I'm sure makes you feel gobs better.
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majicmaker
Well-known member
Howie,
You're right! This has been WAAAY over analyzed!! If you put the other half of the link on, It will be just fine! Just go Ride it Like you Stole It!! :yahoo:
You're right! This has been WAAAY over analyzed!! If you put the other half of the link on, It will be just fine! Just go Ride it Like you Stole It!! :yahoo:
CHRIS_D
Well-known member
Ok so where do I buy this bar at?
lnewlf
Well-known member
I basically did the same thing to the torque link when I put a FZR1000 wheel and 190 spec tire on my FJ1200. Moved the link to the outside of the caliper and the mount on the swingarm. Then ran the hell out of it for 55K with no issues at all...The caliper mounting bracket , being also a wheel spacer is clamped under mondo pressure when the axle nut is torqued, and doesn't need much support from the torque link.
Patriot
Isabella is Lazarus
Holy Smoly...would you guys quit this
Just wrap the strut with duct tape and attach the ends with bailing wire
Sheesh...
:yahoo:
Just wrap the strut with duct tape and attach the ends with bailing wire
Sheesh...
:yahoo:
RadioHowie
I Miss Beemerdons!
I'd recommend wrapping the tape longitudinally to make the most out of the tape's inherent structural strength, rather than rely on the adhesive capabilities.
:****:
demetri
Well-known member
just do this:
RadioHowie
I Miss Beemerdons!
Gawd....look at all the heat damage you caused grinding that thing down. It's SURE to fail!just do this:
RadioHowie
I Miss Beemerdons!
Walter, just look at your "Riding Map" in your sig line....
How'dyou get to Texas without going through Mississippi and Louisiana???
[SIZE=8pt](and to keep "on topic")[/SIZE]
Were you on a Car Tire when you went to Texas???
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I strongly recommend you DO NOT do this. The stock part is a boxed aluminum piece made from a sheet, folded into the box. the 'seam' is not welded, it's just butted up to itself. As a box, the part is very strong. A box with a side cut out of it, is significantly weakened.just do this:
The steel bar is probably stronger than the stock aluminum part and not that difficult to make.
Chris D - Email Farklemasters and ask, they will sell you one. It's just not a listed part. Contact link
Patriot
Isabella is Lazarus
Howie, you really need to quit drinkin', OK buddy???Walter, just look at your "Riding Map" in your sig line....
How'dyou get to Texas without going through Mississippi and Louisiana???
from: https://www.fjrforum.com/forum//index.php?s...=29470&st=0
oh, your welcome
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