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Re: Are suppliers shipping the wrong rocker Oring?
John Healy #468684 12/21/12 3:52 am
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Something wrong with that calculator, John. If we plug in the numbers for an -011 ring (0.1505 for r--which is half of the 0.301 ID, and 0.2205 for R, which is r + the 0.070 cross section), it gives us almost 0.1 cubic inch--that's a slab of rubber 0.100 thick (thicker than the O ring) by 1 square inch. Clearly a bad result.

I tried to tell them in their little tutor box, but they wouldn't listen unless I signed up. Their loss.




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Re: Are suppliers shipping the wrong rocker Oring?
ed_h #468686 12/21/12 4:05 am
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I see what they did wrong. It's the drawing showing the r and R dimensions. R should be the radius of the centerline of the ring (halfway between ID and OD), and r should be the radius of the rubber (half of the 0.070 cross section for the -011).

Also, the formula for the groove volume is different because it is a square section instead of round.

For the groove, volume would be depth x width x PI x mean diameter (diameter halfway between ID and OD).




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Re: Are suppliers shipping the wrong rocker Oring?
Snakeoil #468694 12/21/12 5:36 am
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Originally Posted by Snakeoil
...why not look at smaller o-rings and see if an 010 or smaller might not work


Rob--
Here is the table with the -010 included:

[Linked Image]

Looks like the -010 might fit in the groove, but the stretch would be very high. I don't know exactly what happens with high stretch, but the sources say it reduces the life of the seal. Apparently stretches less than 5% are considered ideal.




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Re: Are suppliers shipping the wrong rocker Oring?
ed_h #468721 12/21/12 1:42 pm
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Here's an oddball- albino o ring: 70-7431 for crankcase drain and adjuster plug.(2 different items)
[Linked Image]
Originally Posted by Legend Cycle
(70-7431) O-ring
oil scavange pipe.


There are no sizes or spec's for this item?
Anything special about it?

[Linked Image]

Here's the actual plug:
[Linked Image]


1978 Bonneville T140V PX
Re: Are suppliers shipping the wrong rocker Oring?
JBMorris #468722 12/21/12 2:13 pm
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I believe the white O ring seals the top joint of the oil scavenge pipe to the crancase on a late model Daytona and is either silicone or ptfe.
.

Re: Are suppliers shipping the wrong rocker Oring?
Old Cafe Racer #468724 12/21/12 3:31 pm
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From the beginning of this discussion, I thought that stretching the 011 ring was compromising the life of the ring. Not sure what kind of creep a material like nitrile sees over time at elevated temps. But to your point, if there is a specified range of stretch, then it much be based on the material properties. Otherwise, they would have larger steps between the standard sizes with each size fitting a broader range of groove diameters.

I was not aware that o-rings are a relatively new sealing component developed during WWII. Given the materials used for the first designs and the limited knowledge of how they react under all conditions, I could see Triumph coming up with the ring that is similar to the 011 and just stretching it to fit. It could very well be that the original o-ring they used came from some other application and they just applied it to their design. If you consider the time frame, not that much time had passed when bike engines had open valve trains and total loss oiling systems. So the original rockerbox design may have been a press fit of the cap into the rockerbox and the o-ring was applied as an afterthought. Afterall,why would the cap be a separate piece when that shaft could have been machined from one piece of steel? I venture a guess it was to allow oversize caps to restore the press fit when necessary. The application of the o-ring eliminated the need to change caps, but they kept the 2-piece design.

regards,
Rob

Re: Are suppliers shipping the wrong rocker Oring?
Old Cafe Racer #468729 12/21/12 4:09 pm
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Originally Posted by Old Cafe Racer
...how is it that some people are able to assemble these O rings by various means without removing any rubber?


OCR--

I've wondered this myself. I'd assume some are getting the skinnier ring. Then I'd bet there those who slap the spindle home and don't even notice the little shaving of rubber. There are also those out there who think it is normal to shave the ring. If there is a taper on the rocker box bore, the sliver of rubber can hide in there and not even be seen until the next disassembly. This happened to me.



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Re: Are suppliers shipping the wrong rocker Oring?
ed_h #468740 12/21/12 6:07 pm
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[quote]Afterall,why would the cap be a separate piece when that shaft could have been machined from one piece of steel?[quote]

That is a no brainer! - cost!

Re: Are suppliers shipping the wrong rocker Oring?
John Healy #468783 12/22/12 12:15 am
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Do you really think it is cheaper to make two pieces that have a pressed fit and then assemble them than to make one piece? I'm not sure I agree with that. The end of the spindle that enters the cap needs to be a close tolerance to maintain the press fit. Maybe it is the same OD as the bearing surfaces and hence ground to size at the same time.

Oh, wait, as I'm typing this I suspect I know the reasoning. I'll bet the shaft is drilled all the way thru and the cap plugs the one end and also makes it presentable. Since the shaft is ground, it would require a center be drilled on each end. If the cap were part of the shaft, they would have to face off the cap when they were done with the grinding process and since I would think the shaft is hardened, it might not be a simple as chucking it in a lathe and facing it off. But I tend to think the real reason is to cap of that oil passage.

I just went out and ran a wire thru my spindles. They are drilled thru. The cap is there to block off that end. I'm pretty sure the reasoning for the cap is to assure the drilling process can be followed up by cleaning process to remove any chips. It's a conservative engineering design decision, not a cost savings IMHO.

regards,
Rob

Last edited by Snakeoil; 12/22/12 12:22 am.
Re: Are suppliers shipping the wrong rocker Oring?
ed_h #468789 12/22/12 1:04 am
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Until I had some made a couple years back the cap was never available as standard, or oversize, from Triumph.
Although the 70-1512 shaft goes back to WWII the :O: ring wasn't introduced until 1952. The 60-3548 showed up in the parts book in 1972, but was used in production as far back as 1970. There was no change in the dimensions in the groove. If someone was to machine the rocker boxes on modern CNC machinery you would groove the box to hold an "O" ring and taper the shaft for insertion.

Cost is still the factor when considering making it one piece vs a two piece arrangement. You would have the additional machine time removing all of the material up to the shoulder before heat treating and grinding.

You would have to address how you were going to hold the shaft for grinding as you would lack a center hole in the drive side end. This type of deep hole is best drilled from both ends meeting in the middle. Drilling the hole can be include center drilling the the end as part of the set-up. Or as you mentioned above, if it was one piece you would have to have an additional machine operation to cut the face flat after it was hardened.

Grinding to a shoulder is always more difficult in a production operation than a straight shaft. If it was one piece you would be drilling a deep blind hole. This type of deep hole is best drilled from both ends meeting in the middle. Remember these parts were made in the day of the shaper, gang drill presses and drilling/reaming boxes not automated CNC machinery.

If you are worried about the space available for the "O" ring why don't you just widen the groove?

And I have been silent, but yes I can put one of these "O" rings into the box without cutting it - and have verified this by pushing the shaft back enough to allow checking! It can be done... Do you get 10 out of 10, of course not. But I get a lot more right than not andt moving the shaft back out a bit allows you to check.

Re: Are suppliers shipping the wrong rocker Oring?
John Healy #468793 12/22/12 2:15 am
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That's interesting that the cap was indeed used initially without an o-ring.

You make valid points about grinding to a shoulder, John. That does make it less than a straight forward grinding operation. Long small hole machining makes sense, too. I stand corrected.

Thanks for the details.

regards,
Rob

Re: Are suppliers shipping the wrong rocker Oring?
Snakeoil #469049 12/24/12 2:41 am
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After all the discussion and the good input, I'm pretty convinced that the -011 O Ring, often supplied as part number 70-3253 is not the correct part, at least for a 71 T100R.

The skinnier ring (possibly a metric 1.3 x 12), which may be supplied under PN 60-3548 is much more likely to work, though he gland fill is still very high. I'm thinking about making the groove a few thou wider so the ring/groove at least conform to modern engineering standards.

By the way, here is a closeup pic of the damage done to an -011 ring, installed with lubrication and a smooth gradual taper. Notice how the sheared off piece left a spiral groove in the ring.

[Linked Image]

Last edited by ed_h; 12/24/12 7:32 am.


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Re: Are suppliers shipping the wrong rocker Oring?
ed_h #469247 12/25/12 5:39 pm
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I've got a handful of o-rings that look like that with varying depths of snipped material. The ring appears to rotate about it's CS diameter. On my rockerboxes, the outside face of the hole, which is really the chamfer did not seem to be square to the bore axis and when it nipped the ring it always seemed to start on the same side. Using John's method I could get most of the ring in but would squeeze out where there was more room to extrude out due to the lack of squareness. When I tried using the tool without modification or even when I tapped the spindle into the tool and it would snip off a small ring, the damage was not always on the OD of the ring. Often, it was on the a vertical plane relative to the OD of the ring. So this told me it was turning as it was grabbed. I had several instances where it snipped a perfect ring and when disassembled, the damage was on a vertical plane. This means the ring probably would have sealed fine. This could account for folks snipping the rings at installation and still not getting leaks.

I also got a spiral cut like yours, Ed, on a few occasions. Probably one rockerbox cut a different pattern than the other.

regards,
Rob
regards

Re: Are suppliers shipping the wrong rocker Oring?
ed_h #469394 12/26/12 10:50 pm
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This is a 70-3253 "O" ring in a 500 rocker shaft out of one of my 500 racers. This saw several years of use without leaking oil. The bike was routinely brought over 9,000 rpm. Notice there is no signs of burnt oil outside of the "O" ring.

"O" ring click here to see "O" ring!

Re: Are suppliers shipping the wrong rocker Oring?
John Healy #469424 12/27/12 7:51 am
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Well, there does appear to be some anecdotal evidence from knowledgeable people that the -011 ring can be stuffed into a stock 500 gland. I have to accept it at face value, but also can't explain it given what the numbers show.

At a minimum, a couple of things are clear, though: Successfully fitting the -011 ring gives many people a lot of trouble, and even experienced people aren't successful every time. Also, the relative dimensions of the gland and ring predict that it will be a difficult install at best.

There is also the existence of the skinny ring, which does fit the 500 gland.

One question, John--which models list the 60-3548 as the spindle ring?




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Re: Are suppliers shipping the wrong rocker Oring?
John Healy #469467 12/27/12 3:45 pm
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As I went thru the learning process, I had a few o-rings that looked very close to that picture John posted when I pulled them back out. The snipped rubber was more like a piece of Saran wrap in thickness. I really could not tell it had snipped anything but the root of the chamfer looked dark. So I went in with a dental probe and came out with something that was so thin it was like black snot. I should have saved some for your Ed. You could try to calculat the volume to see if that was the excess you calculted won't fit. grin

This discussion of whether or not the 011 o-ring works reminds me of when I was a field engineer, I remember a call to design engineering over a problem we were having with a gas turbine. We needed their approval to make a mod. Engineering was demanding we bring the components into spec. The machine was distorted from years of service and it was going to be close to impossible. This was in a 3rd world country, long before computers and cell phones and it could take a day to get a call thru to the US. It had become a circular argument. Finally the lead field engineer screamed into the phone, "Do you want it to run or do you want it to be in spec?!". There was silence on the other end. We made it run.

regards,
Rob

Re: Are suppliers shipping the wrong rocker Oring?
ed_h #469509 12/27/12 7:54 pm
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If you were to take you lead from the parts books that would be 1972, but like the 650, addendum sheets to the 500 parts books date the change back to 1970.

We supply both of these "O" rings in our gasket kits as we have dealers who like one or the other. I had tried to trace the change in "O" rings to a change in the depth or width of the groove. I checked every shaft I could get my hands on and never found one that had different dimensions. So it appears they changed the spec. of the "O" ring with out making any changes to the shaft.

The 70-3253 "O" rings in out kits does not look like the one on your pencil. There is a microscopic bit of flash on the edge, but not as much as the one on your pencil.

If we found a better "O" ring you would certainly find it in our gasket sets. That said I have never found one, nor has anyone offered suggestions for a substitute. I am listening which is why you find me here.

Re: Are suppliers shipping the wrong rocker Oring?
John Healy #469579 12/28/12 4:29 am
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Thanks, John. That's informative.

So at least for '70-'71 500 and 650 models, the "correct" O ring would be the one listed in the parts addendum sheets as the skinnier 60-3548. Yet many people, including me, have been ordering the 70-3253 (or trying to use the -011) because they don't have the addendum sheets. I assume those with '72 and up bikes are ordering and getting the skinny ring.

I guess this may answer the thread title question: suppliers aren't shipping the wrong ring--owners are ordering the wrong one.

One more question, John--I take it that the pre-1970 models have the same groove size. Is the -011 sized ring (70-3253) still the "correct" ring for those models?

About the flash on the ring--that ring was bought as a standard industrial -011 part, and the standard has a spec for maximum flash. I'd bet the actual flash would vary across manufacturers, and maybe even across lots, and still be in spec.



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Re: Are suppliers shipping the wrong rocker Oring?
ed_h #501529 08/13/13 10:24 am
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Although not specific to o-ring size, I made a conversion that has outlived any other solution I tried.
As have been discussed before on this forum, the spindle actually rest on the o-ring while inserted. This, with time causes the shoulder on the rockerbox to "warp" and thereby causing a leak around the o-ring even when inserted without ripping. That´s why I figured that if you could distribute the pressure to several o-rings, instead of one, it should serve 2 purposes. To distribute the load on more than 1 o-ring, to prevent this warping and offering 3 seals instead of one.
Now I know that there are alot of brilliant britbike repair guys inhere and with good reason they are being quite sceptical about conversions, but this conversion seems to work, at least for me, besides being invisible.
Find a good machinist, to create the 2 extra grooves in the spindle exactly as the original(edge of groove is tapered, presumably to prevent ripping and offering the correct amount of crush). Fitting is not notably harder than with 1 o-ring. (If one goes in without ripping the others should also fit)
[Linked Image]


*******************
Run `em...
*******************
1969 T120
Re: Are suppliers shipping the wrong rocker Oring?
ed_h #501556 08/13/13 4:29 pm
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I had a bad leak at the rocker spindle. I got round all the mathematical caculations by putting some silicone sealant in the groove and on the shaft and fitted the o ring. I tapped it back in with the special tool and may have shaved some rubber but it stopped the leak.

Dave

Re: Are suppliers shipping the wrong rocker Oring?
ed_h #501585 08/13/13 8:59 pm
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I got mine to stop leaking recently .
Question : What do you use to clean the baked on oil ?
Carb cleaner doesn't seem to bother it .
Maybe I'll try Acetone .

Re: Are suppliers shipping the wrong rocker Oring?
PeterJ #501646 08/14/13 4:24 am
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Originally Posted by PeterJ

Question : What do you use to clean the baked on oil ?


Don't....it'll start leaking again!! laugh

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
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