Need Solid Bush!

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jredgrave
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Re: Need Solid Bush!

#16 Post by jredgrave » Tue Nov 11, 2014 2:35 am

Well yes, but I'm asking why the bolt is 12.9. If the bolt at the other end wouldn't sustain the load or the links wouldn't then using Ti instead is an option. But if the load is real I wouldn't want to risk it.

jason

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Speed Freak
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Re: Need Solid Bush!

#17 Post by Speed Freak » Tue Nov 11, 2014 5:01 am

You can see the grade of the bolt on it`s head.
Japanese hexagon head bolts have "8" or "10" on their head which is more or less the same as "8.8" and "10.9"

First number x100 = tensile strength, and out of the second number you can get the yield strength.

If a bolt gets shear load, there is something wrong with the construction.
In this case the friction between frame and bearing collar on one side and the friction between the "special nut" and the small collar on the other side have to support the whole load.

Friction force = Bolt force x friction coefficient.
The maximum possible bolt force depends on the quality of the bolt:

Just for comparison, M10 bolt forces:
8.8: 26,336kN
10.9: 37,034kN
12.9: 44,441kN

Source:
http://www.schrauben-normen.de/anziehmomente.html


This is now the pure theory :D
Would be interesting if there is a specific higher tightening torque for this bolt than for other M10 bolts.
I can check it at home...
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04

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Speed Freak
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Re: Need Solid Bush!

#18 Post by Speed Freak » Tue Nov 11, 2014 3:19 pm

Checked again, sorry... all Yamaha bolts are 12.9 quality. Even the plastic battery box is mounted with a high quality bolt :smt005
Tightening torque is 32Nm => standard value for a 6.8 bolt...
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04

jredgrave
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Re: Need Solid Bush!

#19 Post by jredgrave » Fri Nov 14, 2014 12:01 am

Speed Freak wrote:You can see the grade of the bolt on it`s head.
If a bolt gets shear load, there is something wrong with the construction.
In this case the friction between frame and bearing collar on one side and the friction between the "special nut" and the small collar on the other side have to support the whole load.
But since the special nut is a bit loose in the frame there is bound to be at least some shear load on the bolt. I'm starting to think that a collar on each end of the bolt that is tight to the frame and a 12 point nut might be better than the special nut. I'm dealing with a RZV frame though. The steel frame is a bit different.

jason

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Re: Need Solid Bush!

#20 Post by Smoker » Sat Dec 20, 2014 11:26 am

jredgrave wrote:
Speed Freak wrote:You can see the grade of the bolt on it`s head.
If a bolt gets shear load, there is something wrong with the construction.
In this case the friction between frame and bearing collar on one side and the friction between the "special nut" and the small collar on the other side have to support the whole load.
But since the special nut is a bit loose in the frame there is bound to be at least some shear load on the bolt. I'm starting to think that a collar on each end of the bolt that is tight to the frame and a 12 point nut might be better than the special nut. I'm dealing with a RZV frame though. The steel frame is a bit different.

jason
I think I get it.

The Collar (on the Special Bolt), and the Special Nut, could be custom made to fit "snugly" into the frame and "snugly" onto the Special Bolt.

Do you and Speed Freak agree that this will help the problem?

Has this (relay arm collar cracking) problem ever happened to anyone else?

I'll probably be making these parts from titanium, so it shouldn't be s big deal to make them fit better. I would have, anyway - I never just copy the OEM stuff - already learned that lesson.

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Re: Need Solid Bush!

#21 Post by Speed Freak » Sat Dec 20, 2014 3:00 pm

Yes, this should make the problem at least better.
A high precision part was simply too expensive in mass production, if it fits really tight it should be ok.

I was thinking about a solution with a cone and a slotted collar on the frame side which is getting bigger while tightening that it fits with some force in the hole to prevent it from wear caused by the small movement.

The original load case would kill every needle bearing (maybe the reason why it is the only area they used this stupid plastic stuff)
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04

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Re: Need Solid Bush!

#22 Post by Smoker » Sat Dec 20, 2014 6:56 pm

Speed Freak wrote:The original load case would kill every needle bearing (maybe the reason why it is the only area they used this stupid plastic stuff)
So, what is this stupid plastic stuff? Delrin? Teflon? Something else?

How thick is the plastic stuff, 4mm? I haven't removed them, yet.

I don't understand the amount of load on these parts. Perhaps, the amount of load is too much for roller bearings or bronze bushings with a 4mm thickness.

Maybe plastic is the best choice because it "compresses" instead of cracking like metal. :smt017

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Re: Need Solid Bush!

#23 Post by Speed Freak » Sun Dec 21, 2014 7:41 am

Dimension of the plastic bush: Do 24mm, Di 18mm, L 30,2mm, lubricating groove in the middle inside and outside 3mm wide, 0,7mm deep, connected by 2 holes.
Tight fit in the outer part.
As far as i remember it looked like glas fiber filled polyamide.

Needle/roller bearings are not the best option for such peak loads because of the very small contact points, but they are the best solution in terms of bearing clearance (possible to go down to 0).

A possible reason why they used plastic:
- Needle bearings cracked or worn too early, but they didn`t want to change the whole design
- Bronze is expensive (copper)
- Plastic will distribute the load over the steel collar, even if the load is not 100% perpendicular to the collar axis, it is cheap and it will survive long enough without too much clearance.

But thats just guessing, only the responsible engineer can tell you the real reason.
I think money saving was in case of the RD500 not priority 1, in comparison to the RD350YPVS all the parts are quite expensive.
But the 500 is still a mass production bike and they count every single cent that can be saved :smt002

Good example for such cheap plastic bushings is the RD350 4L0 swing arm bearing.
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04

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Re: Need Solid Bush!

#24 Post by Smoker » Sun Dec 21, 2014 11:49 am

So far, I haven't been able to locate the exact size and style of roller bearing that I want for the relay arms. May be for the better, as roller bearings may not hold up.

Been looking for Super Oilite 16 to shape into proper bushings for the relay arms. If I can't find it, maybe Super Oilite would be okay.

If Oilite bushings don't need a seal - they could be full length 18x24x40.

Even the needle bearings I've been looking at are 18x24x20. I've decided to do away with the grease nipples and the grease seals on the relay arms.

How long will you ride before checking the new relay arm collars for signs of cracking/stress? To check them - the parts have to come apart - so, why not regrease the parts at the same time? This way, the entire relay arm is supported by the bushings/bearings and collars. Also, the Oilite bushings are self-lubricating and should last a very long time.

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Kalim
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Re: Need Solid Bush!

#25 Post by Kalim » Mon Dec 22, 2014 5:54 am

Thanks for this thread, it's a good warning.
I'll have a close look during my rebuild.

David.

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Re: Need Solid Bush!

#26 Post by Smoker » Mon Dec 22, 2014 1:49 pm

I found Oilite bushings for the relay arms (18x24x30), but the length needs to be shaved on one side, which is no problem.

I found Super Oilite bushings in SAE sizes which could be machined to fit the relay arms. The problem is - if the tools aren't sharp enough or if it's done incorrectly, the pores in the bushing will deform and clog, and the bushing won't lubricate properly.

I haven't found a source for Super Oilite 16.

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Kalim
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Re: Need Solid Bush!

#27 Post by Kalim » Mon Jan 12, 2015 4:59 am

Speed Freak wrote:Some pictures:

Image

Image
I removed the suspension system from the frame, as I am preparing it for painting.
One of the two bushes looks exactly the same. Broken identically.

Need to get some new ones machined.


By the way, I've seen on your project topic that you've CAD designed the complete system.
Can you make a section picture in the long bolt axis, so we can see all the bushings, spacers, contact surfaces etc ..?
Did you draw the frame on this area ?
Thanks.

David.

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Re: Need Solid Bush!

#28 Post by Speed Freak » Mon Jan 12, 2015 9:58 am

Yes, I have measured and drawn the bushes in the frame and the whole system.
And i have also checked possible bearing solutions:

I checked the max. static load of the 2 big original bearings on the other side of the relay arms - they get the same load.
Easy way of thinking => i took this max. load and checked with which bearings i can get close to this static load.

1) Caged needle bearings with seals: Not possible, even if the whole area is filled with needle bearings, the possible load is below 1/2 of the other bearings.
2) 4x Koyo 18x24x12 without cage filled with needles: ~2/3 of the original bearings
3) 4x Koyo 18x24x16 without cage, filled with needles: Would work (possible static load slightly above the 2 big bearings), but without gap bewteen the bearings (no function of the grease nipple) and maybe it`s a problem to get the seals completely into the relay arm.

Therefor i think, i will also go for brass bushings shaped like the original plastic stuff.

If you have someone for machining and hardening, please let me know how much you pay for it.
My bikes:
RD500 YPVS 1GE
RD350 YPVS 31K 1985
Honda CBR 1000 RR SC57
Yamaha R1 RN04

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Re: Need Solid Bush!

#29 Post by Smoker » Mon Jan 12, 2015 3:13 pm

Speed Freak - What numbers are you using to compare the bearings and brass bushings?

I found the following:

18x24x16 Full Complement Bearing : 17,600 x 2 = 35,200 Static Load (each relay arm)
Oilite: Static P [psi] = 8,000
Super Oilite: Static P [psi] = 20,000

Not really sure how to compare these numbers for this application. :smt017

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Kalim
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Re: Need Solid Bush!

#30 Post by Kalim » Tue Jan 13, 2015 7:39 am

Speed Freak wrote: If you have someone for machining and hardening, please let me know how much you pay for it.
Hello, do you have machining drawings for the bushes and the rollers ?

I will bring the original bushings to my office, measure the hardness to determine what steel should be used, and measure surface finish to know which requirement to ask for.

If they can be done in pre-treated steel, I'll try to get them done at my office workshop.
I'll keep you posted if I can get some sets done :smile: .

I don't know what I can do for the rollers, yet.

David.

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