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Gazzalene

Tamiya plastic oil shocks,sticking

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The kit supplied  plastic oil filled shocks on my Beetle Blitzer always seem to stick.  Pick the car up after a while and when you move the suspension it feels stiff then you feel it give and its nice and free.

What causes this? I made the shocks well,using slime on the oil rings and cleaning the piston disc of it burr from sprue.

I am thinking of changing these to something else, don't want to spend loads on shocks,is there something anyone can mention?

fast trax and absima are easy to buy in the UK , Yeah is meant to be good but not so easy to get.

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Friction between the extended piston and the o-rings until the suspension is compressed back into the shock body oil enough to lubricate it again.

All oil dampers get this to some extent dont they? 

(apart from kyosho reds as they are continually self lubricating through leakage)

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I thought using green slime eliminates a lot of this. I realise it will eventually get worse BUT they have only been done a few weeks with little use.

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You might consider disassembling the shocks and cleaning out all the green slime; I've never used any sort of slime on any Tamiya black CVA dampers.  If a car has been stored for a while, there might be a little (very little) initial stiction, but the slightest of movement will break them free and they'll work normally.  Just placing the car on the ground causes enough movement to break them loose.  So I can't help wonder if the slime is gumming everything up.

Pretty much the only place I use some sort of sealant is on gear diff gaskets; just a little bit of Permatex black RTV helps guarantee there are no diff oil leaks from TB04 gear diffs, for example.

The only model in my fleet that has really bad shock stiction is a HPI Wheely King; if that car sits for awhile it takes a few full strokes of the shock before the friction goes back to normal.  I suspect the O-rings in this case and just haven't gotten around to changing them out yet.

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Yep, Green slime is for leaky shocks.  I discovered that it's no good for perfectly good shocks.  

 

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5 minutes ago, Juggular said:

Yep, Green slime is for leaky shocks.  I discovered that it's no good for perfectly good shocks.  

 

Interesting, why you don´t find it good for perfectly good shocks?

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4 hours ago, Gazzalene said:

The kit supplied  plastic oil filled shocks on my Beetle Blitzer always seem to stick.  Pick the car up after a while and when you move the suspension it feels stiff then you feel it give and its nice and free.

What causes this? I made the shocks well,using slime on the oil rings and cleaning the piston disc of it burr from sprue.

I am thinking of changing these to something else, don't want to spend loads on shocks,is there something anyone can mention?

fast trax and absima are easy to buy in the UK , Yeah is meant to be good but not so easy to get.

From my experience over the years, Tamiya plastic shocks are one of the best around, or can be at least built to be one of the best around. Can´t speak for Absima or yeah racing though. I´m not sure about the Blitzer CVA´s, do they have the one piece piston rods with the metal piston? Avoid these, as the piston rods do not have a real chrome coating. They tend to have more friction than the others. Also, you probably have the red O-rings in them. They are better than the old black ones, but also still cause a lot of friction. You can swap out one of the O-rings and fill the gap with a Teflon guiding from TRF shocks, so you get less friction, because you only have 1 O-ring. Keep in mind: a smooth shock, also in real applications, carries a light oil film on the piston rod, to lubricate the seal and guide area. The oil film comes out, but travels inside the shock again to make it work smooth. For the O-rings, I would recommend  the clear ones from Tamiya, or when it comes to other Brands, I like the Revolution racing white ones (cheap, durable, low friction). You can even use Tamiya blue-X-Rings, but that requires some shimming and trial and error to get them leak free. Grease is always a good idea, if it is not mineral based. This often kills the O-rings by causing them to swell. Real shock sealings are greased, too, at least for run in on a new shock. 

My tip: Avoid the Absimas, just use the money to improve your CVA´s. ;) If you need help, let me know. 

Kind regards,

Matthias

 

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Aside from really old 80's shocks, most newer shocks have good seals.  Green slime is designed to stick to the rod and o-rings.  If it didn't, it wouldn't work.  By design, it was made to withstand oil pressure.  Hydraulic lock from shocks that has no breather hole is quite strong.  1:1 excavators' actuators can exert tons of force.  Meaning, green smile (I mean slime) has to be sticky to withstand the pressure.  It will also add thin layers to the thickness of rods and o-rings.  The end result is, slowing things down. 

For the new shocks on on-road cars, it was terrible. M06 has motor at the rear of the car.  The front is very light.  If you added green slime to the front shocks, they won't move, even with only 1 drop of oil in the shocks.  I tried Green Slime on a new CVA, and immediately stopped using it. 

But if you have DT03, which ran in dusty fields for a season, and all the dust stuck to the rods chipped away at the o-rings, green slime can work to fill those gaps: no more leaks.  Like anything, Green slime may not be for every situation.  It's good for leaky shocks with bad seals.  [Ooh, I just got a good idea!  I'll add green slime to the Hornet's front o-rings, so it would move slower!!  I thought AW would be too sticky. Regular grease is too smooth. Green slime might be perfect!]  

 

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All my tamiya shocks stick after sitting for a while.

Once moving they work as they should and none of the sticking ones have ever leaked. 

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7 hours ago, Gazzalene said:

Fast trax and absima are easy to buy in the UK , Yeah is meant to be good but not so easy to get.

The generic Chinese alloy shocks sold as Fastrax and Absima amongst other names have their good and bad points. On the plus side, the alloy parts are quite nicely machined and look smart. On the minus side, the plastic parts are brittle, the seals are poor and the assembly is hit-and-miss. You can make them work quite well by disassembling them, cleaning off the moulding flash from the pistons, replacing the shaft seals with Tamiya red o-rings, fitting Tamiya lower eyelets and refilling them properly with fresh oil.

The Yeah Racing ones on the other hand are really rather good. The shaft seals are also best replaced with Tamiya o-rings, and some people prefer Tamiya diaphragms too, but apart from that they are of good quality, not quite TRF standard, but not too far off, while costing significantly less.

Oh, and the sticking is entirely normal. All my shocks do it to some degree after being left for a while, from the most humble plastic CVAs to the top-of-the-line TRFs and everything in between. They go back to normal once compressed and allowed to rebound. I would only worry if they keep sticking after a couple of cycles.

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I find some just tend to do it and some don't. I've never noticed any noticeable increase in resistance from using green slime.

I'd be more likely to point to the cheaper black o rings as a culprit than green slime. Some tamiya shock shafts also seem to have a thin layer of black oxide on them which makes them more clingy.

The DT03 hopup set is a good example, the front shafts are shiny silver and I've never had binding. The rear shafts have that slight blackness to them and always stick. When I come across shafts like this now i just put them in a drill chuck and use some very fine wet and dry paper followed by polish make them silver again. That seems to help.

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