Tech Thread -- SCX10 shocks

[Hardline]

How about we do a tech thread on these shocks. There's bits and pieces of tricks spread all around the forum. Maybe we can gather most of them up here.

I saw a for sale ad from Ittybitty for a car and I think he said his scx shocks had:

axial rod end balls
jeepndoug spring cups for mini-T springs
creation fab upper spring retainers
bleed holes
bladders from 1/16 traxxas

Anybody want to add to this list, or provide details, or put up part numbers and sources? Pictures would be nice. Maybe we can get people like Krawlfreak and DelMonte to give up their secrets.

I'll start with the part number for the aluminum version. AX30090. They come with phony canister caps, but the plastics bag has regular caps you can put on instead. They come dry. Next...

[Calderwood]

Traxxas bladders: tra7062 (I believe these have the least rebound but may not seal a second time after a rebuild.)

Duratrax bladders: DTXC9182 - what I use.

Axial o-rings: axa1179

Associated green slime: 1105

[Calderwood]

Losi mrc silver springs: LOSB1447

Losi mini-t rear springs: LOSB1119

Associated rc18 bladders: 21192 edit: these are really hard and I'm not really liking that they have a slightly smaller od that the duratrax bladders. I could see these getting sucked into the body.

[doublej]

I have dug around a few times looking for all this info - Thanks!
Even links to the threads that are already have tech info would be great....

What is this bleed hole you speak of?

[Hardline]

I can't find the thread for Egressor's shock bodies. Are these no more?

[Calderwood]

Mini quake bladders: DTXC9044 (I think these will work since rc18 bladders work and guys use these in rc18 shocks to get less rebound)

Axial machined pistons: AX30132

[Hardline]

Originally Posted by doublej

What is this bleed hole you speak of?

When you set a cap on top of shock body, it's full of air. When you thread it on that air gets pushed into the shock causing rebound. By drilling a small hole half way down the cap, air can bleed out until that hole gets covered up. So doesn't eliminate, but reduces the problem.

Find Del Monte's XR10 build thread for photos.

[WAM]

Okay, this got me to thinking, and checking back threads. I now kinda believe there is no use for a bleed hole in the side of the cap and here's why. Forget the bladder for now and consider the shock as built -- it's a monotube emulsion shock. Contrary to many local opinions, you HAVE to have air in the shock (all shocks actually). A lot of people go to much effort to get all the air out they can. Which is wrong.

When you fill the tube with oil and raise the piston, the shaft moves from outside the body to inside the body. Fluid has to flow out of it's way and needs some place to go. The shock is sealed, so it can't get out. What it does is press on the air bubble at the top and compresses it to a smaller size, allowing everything to fit.

If you have too little air, the small bubble has to be squeezed really hard to let the shock compress, so it builds up more pressure which causes rebound. The shock wants to extend itself, separate from the springs.

If you have too much air, the piston will poke out the surface and you'll lose damping. So the real issue is to determine how much air is optimum, not how to get rid of it. The amount of air in the cap is too little air for this shock. So there's no need to drill a bleed hole to get rid of some. In fact the trick is to decide how far down the tube the fluid should be before you put the cap on.

A bladder changes things some, but this post is long enough already, so later for that. (ps, bladder still doesn't need a side hole. Top hole, yeah)

[JeremyH]

Originally Posted by WAM

The shock is sealed, so it can't get out.

In a perfect world, yes.....but these are not. That is obvious by the puddle of oil sitting under them when your truck is on the shelf.

Originally Posted by WAM

If you have too much air, the piston will poke out the surface and you'll lose damping. So the real issue is to determine how much air is optimum, not how to get rid of it. The amount of air in the cap is too little air for this shock. So there's no need to drill a bleed hole to get rid of some. In fact the trick is to decide how far down the tube the fluid should be before you put the cap on.

Very true!

Originally Posted by WAM

A bladder changes things some, but this post is long enough already, so later for that. (ps, bladder still doesn't need a side hole. Top hole, yeah)

Again, also true.
A bladder can offer some positives, but it is not a magic wand for these shocks.

[Calderwood]

Originally Posted by WAM

Okay, this got me to thinking, and checking back threads. I now kinda believe there is no use for a bleed hole in the side of the cap and here's why. Forget the bladder for now and consider the shock as built -- it's a monotube emulsion shock. Contrary to many local opinions, you HAVE to have air in the shock (all shocks actually). A lot of people go to much effort to get all the air out they can. Which is wrong.

When you fill the tube with oil and raise the piston, the shaft moves from outside the body to inside the body. Fluid has to flow out of it's way and needs some place to go. The shock is sealed, so it can't get out. What it does is press on the air bubble at the top and compresses it to a smaller size, allowing everything to fit.

If you have too little air, the small bubble has to be squeezed really hard to let the shock compress, so it builds up more pressure which causes rebound. The shock wants to extend itself, separate from the springs.

If you have too much air, the piston will poke out the surface and you'll lose damping. So the real issue is to determine how much air is optimum, not how to get rid of it. The amount of air in the cap is too little air for this shock. So there's no need to drill a bleed hole to get rid of some. In fact the trick is to decide how far down the tube the fluid should be before you put the cap on.

A bladder changes things some, but this post is long enough already, so later for that. (ps, bladder still doesn't need a side hole. Top hole, yeah)

you are completely ignoring the fact that the shaft doesn't have to be fully extended when you seal the cap.

[WAM]

Originally Posted by nigels_world

you are completely ignoring the fact that the shaft doesn't have to be fully extended when you seal the cap.

I didn't address it because the post was long enough. But having the shaft at a particular height is one way of reducing the amount of fluid in the tube before putting on the cap. Exactly the same as having it fully extended but fluid level down a certain amount.

Regardless, the point is unchanged, that a side-cap hole isn't necessary.


Edit: Hmmm....technically not exactly the same. You will have the same amount of fluid and the same amount of air. But the air will be at a slightly different pressure when both are fully extended or compressed which will reduce it's push at full compression, but add a little vacuum at full extension. However, since these devices are scarcely fluid-tight, they're surely not air-tight over a long period and any air pressure difference will probably equalize in short order.

[Calderwood]

Originally Posted by WAM

I didn't address it because the post was long enough. But having the shaft at a particular height is one way of reducing the amount of fluid in the tube before putting on the cap. Exactly the same as having it fully extended but fluid level down a certain amount.

Regardless, the point is unchanged, that a side-cap hole isn't necessary.

You are wrong. If the shock is built at mid travel then the shock will have less positive pressure when compressed and negative pressure when fully extended. It's definitely not "exactly the same".

[WAM]

I've found what I like best is to fill the tube about 1/4" from the top (piston extended and bled).

I tried Nigel's method, and decided having 1/4" of brass shaft showing on an assembled shock worked out about right. Doing it with 1/2" showing caused my shock to not fully compress.

I think either method will work just fine.

[Calderwood]

Originally Posted by WAM

I just hope mine doesn't come over as negative as yours seems to. Have I done something to offend you?

Sorry if my response was negative in your opinion. It was not intended as such. I simply want everyone who reads the thread to leave with accurate information and tip toeing around worried about feelings tends to leave a confusing thread with conflicting information. I hope this thread can stay "positive" and again I truly didn't mean to offend.

Anyway... On to the Scx shock tech.

[WAM]

[ROWDY RACING]

Egressor shock bodies, nuff said...

[Hardline]

Originally Posted by ROWDY RACING

Egressor shock bodies, nuff said...

Link? Mine went dead. I hope that doesn't mean he dropped them.

[ROWDY RACING]

Originally Posted by Hardline

Link? Mine went dead. I hope that doesn't mean he dropped them.

Good thing I stocked up.

[EverettY]

Originally Posted by Hardline

Link? Mine went dead. I hope that doesn't mean he dropped them.

I heard that someone else will be selling them again soon (won't say who) so just keep your eyes peeled

BTW do those of you running the Egressor bodies still have leaking issues?

[Pdog7]

I've read in posts about an "X" ring for the SCX shocks. Anyone have a link? I can't find anything.