Steering Head Disassembly Question

RCinNC

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#1
I'm doing fork/steering head maintenance this week. The forks are off, and I was getting ready to pull the upper and lower steering head clamps so I can grease the bearings. I have the special Yamaha steering head locknut wrench to remove the locknuts, but I have a question. I didn't recognize that weird star shaped hole on the wrench so I looked it up on line and found out it was called a double square. Various sites talked about specific double square bits, but I see that the 3/8" drive on my ratchet (and my 3/8" ratchet extensions) fit inside the double square hole. Have any of you used this wrench with just a 3/8" drive and extension, or do I have to get some sort of a special double square bit? I can't say that I've ever seen one at Lowe's, or a hardware store, or an auto parts store, but I've never really looked for one either.

Some guidance from someone who's done this would be appreciated, before I wreck the locknut wrench and have to get another one.

I've included a photos of the locknut wrench, and the ratchet and extension, so you can see what I'm talking about.
 

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RCinNC

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#3
I'm doubly glad I posted then, because I didn't know that about compensating for the added length of the extension (and I should have known there would be a difference, though I'd have had no idea what the formula was).

I'm going to take advantage of your knowledge a little bit more then, Checkswrecks. I'm attaching a photo of the torque wrench setup I'll be using. Your drawing indicates that the handgrip centerline is predetermined. Is that based on a marking that's made on the torque wrench itself? If so, mine isn't marked in any way to indicate that. If there is no predetermined point, between what two points would I measure to determine the handgrip centerline? Would it be the midpoint of the rotating portion of the handle?
 

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RCinNC

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#4
Oh, and is it true that if the locknut wrench extension is at 90 degrees from the axis of the torque wrench, then that would negate the need for calculating the length of the extension to determine a new torque setting? I've attached a photo of what I'm referring to.
 

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Checkswrecks

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#5
You have a clicker type of torque wrench, as opposed to a beam type. The illustration in my previous post is a dial on a beam wrench. For either type, the distance shown as L would be to the center pivot of the handle. If the handle screws to adjust, like yours does, then measure and use the center of the handle.


But your next post is the easiest way, just putting the adapter off to the side. There'll be a slight error because the distance will be the hypotenuse of the triangle, but it won't be enough to matter.
 

RCinNC

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#6
Thanks Checkswrecks. If I use the 3/8" extension, I'll have enough room to set the locknut wrench at 90 degrees from the long axis of the torque wrench and still be able to clear the fuel tank when I tighten the locknut.

I appreciate your expertise. I'm going to copy your diagram and formula and keep it with my torque wrench for future reference.
 

blitz11

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#7
Checkswrecks said:
You have a clicker type of torque wrench, as opposed to a beam type. The illustration in my previous post is a dial on a beam wrench. For either type, the distance shown as L would be to the center pivot of the handle. If the handle screws to adjust, like yours does, then measure and use the center of the handle.


But your next post is the easiest way, just putting the adapter off to the side. They'll be a slight error because the distance will be the hypotenuse of the triangle, but it won't be enough to matter.
Think cross product - the moment on the torque wrench when it is orthogonal to the small wrench is the moment applied to the steering stem nut. There is no "hypotenuse" effect.

What he reads is what he gets - assuming the torque wrench is in good calibration.
 

RCinNC

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#8
Checkswrecks, is it the same formula that you posted earlier on this thread? It's just as well anyway; I just got done reinstalling the steering head, and I think I goofed on the parts arrangement. I'm attaching a couple photos. The one photo is of a metal washer, about 5/64" thick and about 1 5/16" in diameter. I believe this washer is Number 15 in the parts diagram (it goes on top the upper steering head bearing). When I reassembled the steering head, I believe I mistook a very thin metal washer (almost like a donut shaped shim) that was on top of the bearing for this thicker smaller washer. Can anyone confirm that the thicker washer should be where Number 15 is, and that is should be on top of that very thin metal washer that was stuck to the top of the upper bearing?

In the service manual, it shows a diagram of a torque wrench at 90 degrees from the steering head nut wrench; are you guys saying that it doesn't make any difference how the steering nut wrench is positioned relative to the torque wrench, and I still need to do the calculations to compensate? I'm going to have to disassemble the steering head again anyway in order to put this metal washer where it belongs, and I want to get the torque setting correct since this is a pretty critical area to mess up on.

UPDATE: No, that metal washer isn't No 15 in the diagram. It doesn't fit under the upper bearing cover (it's too small to fit down over the threads where the locknuts are threaded on). Evidently that thin washer that was on top of the upper bearing is No 15 in the diagram. So where did this thing come from? It'll fit down over the steering head tube, but only as far as where the threads begin for the lower ring nut and upper ring nut. It isn't the washer that goes between the ring nuts, because that one's rubber and I have that one. Is it possible that it goes under the steering stem nut, even though it isn't depicted in the service manual? WTF???

ANOTHER UPDATE: I looked on Rocky Mountain ATV's OEM parts catalog for the S10. It shows a washer under the steering stem nut. That's freaking weird, that their parts diagram shows a washer there but the service manual doesn't. Can anyone confirm that there's supposed to be a metal washer under the steering stem nut?
 

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RCinNC

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#9
Okay, I've checked an online torque wrench adapter calculator (http://www.cncexpo.com/TorqueAdapter.aspx), and here's what I get.

Midpoint of 3/8" drive head on torque wrench to midpoint of handle: 11.3"
Midpoint of 3/8" drive head on torque wrench to midpoint of the fastener: 2.3"

Torque values are initial tightening to 38 ft/lbs, then loosen, then retighten to 13 ft/lbs

With a 0 degree offset, this is what I get: 38 ft/lbs recalculates to 31.6 ft/lbs
13 ft/lbs recalculates to 10.8 ft/lbs

With a 90 degree offset, this is what I get: 38 ft/lbs recalculates to 38 ft/lbs
13 ft/lbs recalculates to 13 ft/lbs

According to the calculator, the torque values don't change if the extension is at a 90 degree angle from the torque wrench. Can one of you smarter guys check my calculations and make sure I'm right?
 

holligl

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#10
Checkswrecks said:
I didn't know it was for anything OTHER than a 3/8" or 1/2" drive, depending on whose tool it is.


If you use a torque wrench, which you should, remember to factor in the difference the tool creates in length.
http://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm
Guys - (Edited/corrected) The diagram calculations assume the two tools are fixed as one body, but they are not. The torque is applied through the single pivot point where the torque is measured. If torque is properly delivered (i.e. holding both ends of the wrench), the angle won't change the amount of torque applied as measured by the wrench. (The purest torque could be applied with a T-Handle and a digital torque adapter.) If the extension is at 0* without support at the pivot point, there is an additional lateral force applied instead of the pure torque and the adapter tool calculations need to be applied. At 90* the additional lateral forces goes through the stem, and don't impact the measured torque. Since any counteracting force at the pivot point would be un- calibrated, the 90* angle is the most accurate.

The extender page referenced points out that the torque applied to the center of the stem is greater than that read by the torque wrench. I would assume that since both the tool and the torque have been specified by Yamaha, they don't expect anyone to make those adjustment calculations.

Therefore, if you are using any tool but Yamaha's, you need ensure the length of the tool (E) is the same as Yamaha's. That is the most critical dimension.
 

RCinNC

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#11
The wrench extension I'm using is a Yamaha specific tool, and matches the one used in the service manual. The manual shows this tool being used at a right angle to the torque wrench. I measured the dimensions of this tool, and the dimensions of my torque wrench, and used those numbers in the torque calculator. The torque values I came up with at a 90 degree angle match the ones in the Yamaha service manual. I'm making the presumption that Yamaha meant the tool to be used at a right angle and based the torque settings on it's use at a right angle, which is why they show it at a right angle in the book. My guess would be if someone invented a tool for the steering locknut that worked more like a socket, the torque values in the service manual wouldn't be correct for that tool, and you'd have to use an equation to remove the length of the extension to work your way back to the values for a straight connection to the locknut. Since the service manual doesn't make any mention of applying torque in any other manner but by using the specific extension at a right angle to the torque wrench, I have to assume that the torque settings of 38 ft/lbs and 13 ft/lbs are correct for that configuration, without any additional calculations. That's how I did my locknut, anyway. I guess if I'm wrong, I'll know soon enough.

This just seemed like a common enough maintenance item that I figured someone who'd done it already would say how they went about it.
 

RCinNC

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#13
Mission accomplished. Just got back from the test ride, and all appears well. It actually seems to dive less on hard braking now.

There was no headshake on the ride, so the manual's torque settings and the right angle extension and torque wrench seemed to be the way to go.
 

holligl

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#14
RCinNC said:
Mission accomplished. Just got back from the test ride, and all appears well. It actually seems to dive less on hard braking now.

There was no headshake on the ride, so the manual's torque settings and the right angle extension and torque wrench seemed to be the way to go.
Mission accomplished! Did you do the initial torque, loosen, and re-torque to final spec? I assume this "seats" the bearing. Where did you get the adapter tool, and what did it cost? It would be nice if you could rent one, for as infrequently it is needed.
 

RCinNC

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#15
Yes...torque first to 38 ft/lbs, then loosen completely, then retighten to 13 ft/lbs (if I remember correctly, I'm not looking at the manual at the moment). I bought the the tool on eBay about a year ago, in anticipation that at some point I'd be doing this. I don't recall what I paid for it, but I do remember it was cheaper there than what Yamaha wanted for it. I think any decent machine shop could make one very easily on a CNC machine. I's prefer someone made a specialized in line socket that fit the recesses on the steering head nut; that would make it a LOT easier to itghten. It wouldn't be difficult; the steering head nut is a lot like a bottom bracket on a bicycle, and my BB tool is just a metal cup with teeth cut into it.
 

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#16
This thread, while interesting in a geeeeeky-engineering-calculus way, gave me a minor headache. I shouldn't have fancied myself capable. ;)
 

holligl

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#17
snakebitten said:
This thread, while interesting in a geeeeeky-engineering-calculus way, gave me a minor headache. I shouldn't have fancied myself capable. ;)
Not trying to make your head explode, but I did edit/correct my answer. Now let's go ride!
 

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#18
Forgive me for resurrecting this thread. I have done so because I believe it does leave some unanswered questions. The discussion so far has centered on the Yamaha tool for tightening the specified nut and a torque wrench.

Again forgive me if I missed something. What if you have a different scenario as in the example of the pictures attached, do the calculations provided above change? Observe that here the torque wrench directly attaches to the steering nut.

Furthermore, does the same torque measurements provided in the service manual still apply or do we have to calculate using the above formula?
 

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