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Tamiya mini cooper

Old 02-20-2013, 12:51 AM
  #18421  
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Thanks!

Regards Robert
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Old 02-20-2013, 02:53 AM
  #18422  
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Originally Posted by Granpa View Post
DO NOT, I repeat, DO NOT build your shocks as shown in that blog. If you do, you'll ruin the o-ring. The likelihood of getting a shock that leaks is quite high following those directions. The correct way is to extend the shock shaft piston assembly thru the shock body, lube the shock shaft threads, slide the o-ring over the shock shaft. Then the small plastic spacer, then the larger one, watch the orientation, then and only then screw one the cap.

When you put the o-ring and spacers in the or on the shock body, and then screw on the cap, you will compress the o-ring slightly. This will make the hole in the o-ring smaller. Shoving the sharp threads of the shock shaft thru a compressed o-ring, even if you lube or green slime it, will damage the o-ring. The o-ring was designed to compress onto the shock shaft when the end cap is tightened. This is what gives you the seal.

Now, Sosidge, whose opinions I often agree with, inadvertently opened a whole new can of worms. The method he described for filling the shocks will give you a shock with a lot of rebound. This may be what you want on certain track surfaces and layouts. In other situations you may want a lot less rebound or even zero rebound. I'm not going to post how to do this, but most good TC drivers can show you.
Thanks very much for this view as well. I will disassemble and carefully examine in the coming days. I have spare o-rings so will replace them at the same time in case I've damaged any.
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Old 02-20-2013, 07:14 AM
  #18423  
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Damage won't be easy to see short of finding your shocks leak. Or maybe I am too old.
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Old 02-20-2013, 09:22 AM
  #18424  
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I discovered a leaky damper last night. It's only the second time ever, but it was the bottom cap backing off. Dang.
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Old 02-20-2013, 11:03 AM
  #18425  
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Since we're all seeming to focused on shocks right now, I've got a question. Every time I change shock oil or rebuild a set of shocks, the oil in the shock is almost black. If it were dirt working it's way up the shock shaft, wouldn't that wear to the o-ring very quickly???? Also wouldn't there be a wear spot on the shock shaft???? I usually have shocks go a year or more before replacing o-rings and the shock shafts show no appreciable wear.

One of the local gurus opined that it came from the shock body. Wasn't going to argue with him cause he's usually correct and has been doing this for a long time. Can't see how this would be, but it's hard to imagine that much dirt working it's way past the o-ring and the the plastic wiper.
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Old 02-20-2013, 11:23 AM
  #18426  
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Originally Posted by Granpa View Post
Since we're all seeming to focused on shocks right now, I've got a question. Every time I change shock oil or rebuild a set of shocks, the oil in the shock is almost black. If it were dirt working it's way up the shock shaft, wouldn't that wear to the o-ring very quickly???? Also wouldn't there be a wear spot on the shock shaft???? I usually have shocks go a year or more before replacing o-rings and the shock shafts show no appreciable wear.

One of the local gurus opined that it came from the shock body. Wasn't going to argue with him cause he's usually correct and has been doing this for a long time. Can't see how this would be, but it's hard to imagine that much dirt working it's way past the o-ring and the the plastic wiper.
How long does it take for the oil to turn black?
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Old 02-20-2013, 11:59 AM
  #18427  
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Originally Posted by jha07 View Post
How long does it take for the oil to turn black?
Don't really know. I'm not one who changes shock oil or rebuilds shocks very often.

When I'm trying to figure out what shock length, rebound, and shock oil to use, I'll change almost every run so the oil remains clean.
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Old 02-20-2013, 12:12 PM
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Originally Posted by Granpa View Post
DO NOT, I repeat, DO NOT build your shocks as shown in that blog. If you do, you'll ruin the o-ring. The likelihood of getting a shock that leaks is quite high following those directions. The correct way is to extend the shock shaft piston assembly thru the shock body, lube the shock shaft threads, slide the o-ring over the shock shaft. Then the small plastic spacer, then the larger one, watch the orientation, then and only then screw one the cap.

When you put the o-ring and spacers in the or on the shock body, and then screw on the cap, you will compress the o-ring slightly. This will make the hole in the o-ring smaller. Shoving the sharp threads of the shock shaft thru a compressed o-ring, even if you lube or green slime it, will damage the o-ring. The o-ring was designed to compress onto the shock shaft when the end cap is tightened. This is what gives you the seal.

Now, Sosidge, whose opinions I often agree with, inadvertently opened a whole new can of worms. The method he described for filling the shocks will give you a shock with a lot of rebound. This may be what you want on certain track surfaces and layouts. In other situations you may want a lot less rebound or even zero rebound. I'm not going to post how to do this, but most good TC drivers can show you.
I learned something today, thank you!
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Old 02-20-2013, 12:41 PM
  #18429  
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And might I offer the information that Tim qualified second in a major meet down here last weekend only to discover that both his rear shocks were almost completely empty....
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Old 02-20-2013, 04:57 PM
  #18430  
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Originally Posted by tony gray View Post
And might I offer the information that Tim qualified second in a major meet down here last weekend only to discover that both his rear shocks were almost completely empty....
Interesting information that proves a number of things. The first being that Tim is a helluva driver. The second being that in an open tire series, tire tuning is far more important than than chassis set up. Better tires trumps better chassis set up every time. Rear shock length and spring may be more important than the shock oil.

Having to run a Spec tire does change the equation a bit and makes this preoccupation with springs, shock oils, etc. more applicable. Not saying one is better than the other. Open tires lead to having lots of different tires. Spec tire guys have lots of springs, shock oil, and a shock pump.
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Old 02-20-2013, 06:07 PM
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Just stirring Bob (of course)

Actually I recall Tim putting solid struts on his car once and he was still within a couple of tenths of his normal lap times.
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Old 02-20-2013, 07:27 PM
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...or the rest of you are $%&# drivers.
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Old 02-20-2013, 11:07 PM
  #18433  
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Originally Posted by Granpa View Post

[...]

One of the local gurus opined that it came from the shock body. Wasn't going to argue with him cause he's usually correct and has been doing this for a long time. Can't see how this would be, but it's hard to imagine that much dirt working it's way past the o-ring and the the plastic wiper.
I am not sure if we're talking alloy shocks or plastic here. If they were plastic, I guess it would be surmised the impurities would be plastic shaved off the damper wall by the piston, so I'll discount that.

But even if alloy, I guess the answer is the same. The alloy on the sidewalls of the damper body will show wear as will the shaft. Aluminium oxidises black in those microscopic chips.

I have found wear both on the shaft and the damper walls. I never found a speck of dirt inside though, and I don't think it can get in short of a catastrophic failure of the shock or careless assembly. If it did you'd know about it from the scratches it would leave behind on shock shaft and damper body. The size of that detritus is way below the size of the tiniest speck of space dust (think about 2 microns).

There are two different types of wear on the shaft. There is polishing and matt wear. I found the polishing is due to the o-ring and matt wear due to dirt shaved off the shaft by the plastic collar below the o-ring. This is most obvious in off-road. Wear on the wall inside the damper is a really high polished oval surface, much more shiny than the original factory finish and sometimes with a wavy surface.
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Old 02-21-2013, 01:07 AM
  #18434  
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Originally Posted by monkeyracing View Post
...or the rest of you are $%&# drivers.
Nah, Tim's a helluva driver.

Originally Posted by tony gray View Post
Just stirring Bob (of course)

Actually I recall Tim putting solid struts on his car once and he was still within a couple of tenths of his normal lap times.
Looks like you and Jim are both doing a little "stirrin". I'm a little bored with the Mini deal right now cause every car I have is just dialed. I'm even starting to put together a SWB M05, but lost enthusiasm for the project part way thru. Spending way too much time here.

Tony Tam did the strut deal a # of years ago also. Car was fast, but Tony felt it was a little weird to drive. Tony like Tim is one of the best Mini guys in the area.

And to niznai, thanx for the response. I think I get it, but there are times you get a little over my head. Some of your explanation never even occurred to me. In fact had to read it several times and ponder a bit, before I got what you were saying.

To SC8E---You're welcome

Last edited by Granpa; 02-21-2013 at 01:09 AM. Reason: spelling
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Old 02-21-2013, 02:21 AM
  #18435  
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Hi Granpa,

I used to run rubber shock booths (i.e. rubbers) covering the springs to prevent dirt from entering the shock oil. Try it, if it still gets dirty then it is coming from within the cylinder.

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