Wednesday, September 04, 2019

Wltoys 12428b (part 20: Oil filled standard rear shocks)

So, I'm very happy with the CVA suspension upgrade.  If i could justify it (and if the parts were available) I'd upgrade the other cars too.  But i can't and they're not.  So what I'm left with is trying to make good on the stock rear suspension.

  1. It's very stiff especially compared to the horizontal front.
  2. Ride height is quite high which accentuates body roll issues
  1. I have multiple spares
  2. Trivial inspection shows all the makings of something better.
NOTE: High precision drafting skills.
I'm not the first person to suggest filling these with oil. There is even a mysterious and seemingly useless little plastic tube (2.55mm x 4.85mm) located exactly where the o-rings would go (as per my recent experience with the CVA shocks).

Option 1: use the standard plastic o ring:

Kevin tells me the oil i needed was around 800cps (which he then retracted and suggested 1000cps).  I have some 750cps, so I've used that.

There's nothing like a categorical No.
Within a heartbeat it all just bubbled out the small end..

Option 2: source proper o rings:

So off to the internet i go to find some appropriate o-rings.. Looking online they're specified using their ID (internal diameter) 2.55mm and their CS or t (cross section) which for me is ~1.1mm (~4.8 - ~2.6/2).  So check out these guys.. this is a list of o-rings of various types .. or some reading on this extensive post suggests these will work

But before i got around to purchasing them..

Option 2a: Use some crappy foam instead of proper o-rings:

..I literally found this on the lab floor, i have no idea where it came from.  It's some kind of foam rubber:

it just .. appeared

I fashioned an o-ring around the shaft of the piston (in place of the small plastic o-ring), and also another around the large end cap.  It worked well enough to see that o-rings won't help..

the second issue is that the springs are very stiff.

Option 2b(?): Cut the springs..

I thought shorter springs = softer.  But it doesn't really seem the case.  It seems they're just .. shorter.  I wish there was more i could say, but even cut they don't seem to be any softer.

Option 3: Just do it properly..

Really.. these just work.  Unless you're on a total shoestring, just do it.

Engineering works..

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