Build questions.
 

Most of the build on the car is covered in the instructions but I do have a few things that I may have overlooked. When it comes to the diffs, what side of the car does the outdrive with the screw and thrust go? Does is matter? What should the belt deflection be on the front and rear belts? What other pistons (losi, AE, Kyosho etc) work in the shocks? And lastly, when doing the shock blader mod, do you cut the whole thing out so you just have a o ring or do you just make a hole in the center? Thanks in advance!
chris

The direction of the diff doesn't matter, as long as you have locked them with the grub screw they should never loosen.

Belt deflection? Whats that? Just set them as per manual, I find the front on the Lipo car is too tight so slacken it by one notch.

Other pistons? No need & I don't know the answer. But im sure somebody else will confirm what will/won't fit.

If you cut the bladder, then remove just the baggy centre, not the O-ring outer. I haven't done this and can't see any benefit, the shocks built as per manual are amazing. Im sure somebody will describe the benefits of doing it for me and you.

thanks for such a fast responce. What I mean by belt deflection is the tension basically. I remember in my cougar 2 instruction book it showed you how to set the tension on the belt but I did not see any way to measure the slop in the sx belts in the instruction.

Thanks for clearing up my other questions for the most part:)

For belt tension, i run 1 setting looser than central - if you assume that the mark straight up is centre.

Pistons - Losi and AE don't fit, not sure about any others.

For Worksop ...........

Are you guys running the front one way with the std layshaft ? ( Chris and Matt )

Can i assume that a "locked" one way layshaft works exactly the same as the std layshaft as supplied with the kit ?

Have both of you guys took the 3mm or so off the top of the front yokes and fitted the ball joints flush minus any washers ?

Thanks muchly :)

Smart question, sure I would also like to have the answer ;)

Hey Rich,
Yes I am running a oneway layshaft without the pin. If you were to fit the pin then it is effectively the stock layshaft = locked.

The front yokes, I think you mean the castor blocks? Im never sure what to call them either but Matt White corrected me a few weeks ago, but yes - I cut mine down flush and then drill the hole right through so then the balljoint will go in and sit flush.

If you read the setup sheets and the team guys run 0mm, this is actually the castor blocks cut. The stock blocks have 3mm moulded onto them and this is too much camber change, even with the inside ballstud mounted with 0mm washers.

Chris

Cutting out the bladders will give less initial pack?

Its probaly more noticable outdoor where tracks are more "natural" :thumbsup:

Cheers Lee,
But the theory (in my own mind) is that the bladder holds a volume of air which is taken up when the shaft plunges. So with no bladder there is no volume to compensate, and the shock pressurises more at plunge and so isn't so linear in damping when it gets to full plunge.... I think this is what I don't like about AE shocks and why I can't build two the same without having a few attempts at it.

This is in my own mind though, and so aware it is likely to be wrong.

With no volume to compensate the shaft wouldn't budge at all - the air is still there but is allowed to mix with the oil.

With a bladder in though you are actually reducing the volume of the shock as well.

Does the shock use a bit of foam above the bladder as a compensator? If so leaving this out will reduce pack slightly but then the next step is cutting out the centre. I agree with what you say Chris, the bladder ensures there is an equal amount of oil/air in each shock, but i think as the piston moves the higher pressure is a bove the piston on compression and this in theory is pushing on the diaphragm as there is a lower volume of fluid above the piston and i think this is where the feel of more pack comes from, if that makes sense :confused:

has anyone ever thought of drilling a hole in the cap while using the bladder so the bladder does not hold air? the air in the bladder can escape to the outside world (and get back in again)?

NOTE: - its just a theory, I have never seen a proper Cat SX shock

I thought about suggesting that chris but i didnt want people to drill a hole and have to buy new shock caps if it becomes "the norm" to run bladderless.

you could always run a thread through it and then use it as a blead screw like the Yok ones ??

that would be pretty cool, then you could 'set' the amount of air in the bladder and then seal it, so you could adjust the rebound or suck just by loosening the screw, compressing or extending the shock and then tightening the screw up again, this could be done 'on the fly' almost!

but also very confusing to the less technically minded, at the end of the day though these are race cars and knowledge is power

When you cut the bladders you are effectively building the shock with no air in it at all right? As it's possible to bleed the shock through the little bleeding hole before tightening completely. That is how mine was done anyway.

The way I understand it is that pack comes from the oil rushing through the holes and by the sides in the piston very quickly. This agitates the molecules which rub against one another and causes friction and resistence, effectively stiffening up the oil. Thinner oil and smaller holes create better pack.

So that would mean on fast compression pack occurs in the lower part of the shock as the oil is rushing down through the holes. Having a bladder in the top will effectively lessen pack because there will be less pressure in the upper part of the shock as the air compresses inside the bladder (until the air compresses fully that is). By cutting the bladder out and building your shock with no air you should in theory get better pack for landing jumps while being to able to use softer oil for better small bump absorbtion.

There are bleed holes in the shock caps, and when the cap is tightened the hole is sealed- this is why the O ring of the bladder has to be left in even if the centre cut. So in effect it does what you say, but the hole is not covered from the outside, to adjust the rebound you would have to remove the shock, loosen the cap, set the piston position to suck in or blow out air, then tighten the cap.

Whether the air is in the oil, or in the bladder, the air will compress. But with the air in the oil its hard to balance the amount of air, and with that air going through the piston then it leads to unbalance. When that air is in the bladder I personally can make shocks balance on first attempt.

I could be wrong ofcause, im only theorising in my mind. This thread is really interesting. :thumbsup:

Frogger, there has to be air in the shock in order for it to work, the piston will be locked "packed" if there is no air in there ;)

I am also of the opposite theory in that there will be more pressure further up the stroke i think that shaft speed will be at its highest in the first part of the shaft movement, as the oil, piston holes and the spring should all slow down the shaft speed if they are doing their job correctly, i cant see an advantage to having a bladder other than making the shock easy to build.

let me explain my adjustable bladder idea.

in the cap, there is a screw that can be opened to let air 'into' the bladders air pocket.

you build the shock as normal with the bladder.

you can run it without the screw so that you have pure (as pure as possible) oil for the piston to move in, and the volume compensation has no pressure against the compensation, so in theory you will have no suck or no rebound.

have the screw done up with the shaft is fully extended to have the some air trapped in the bladder and provide resistance to volume compensation so will provide some rebound to the piston/shaft

have the screw done up with the shaft full pushed in will provide a bit of a vacuum in the air part of the bladder and this will provide some suck for the shaft.

this should be easily adjustable while the shocks are on the car??

Not if there is enough give in the surrounding materials (shock cap and body, o-rings, half cut rubber bladder, etc.) to compensate. Especially if you compress the shock shaft half way to bleed the shock in the first place. My shocks are completely air free (or as best as I could bleed them) and work just dandily :D

As for pressure, I'm no hydraulics or suspension engineer and it's an extremely complex subject so I am very open to be convinced otherwise :)

I tested early in the year running normal bladders (uncut) and ones with foam compensators behind them. Personal preference for me is that with a bladder in fully, the car does generate too much initial pack. Tracks like Coventry with many small bumps and large jumps to clear meant that I felt the car wasnt responding correctly, due to packing out too fast.

By cutting the diaphragm you are essentially making an air/oil shock which is true. I find that the bleed hole in the top of the shock works perfectly to get the correct amount of recoil on each shock, never had a difficulty with this and have found Schumacher shocks easier to do than Associated.

I have started running 3 hole pistons to generate the pak i want with slightly stiffer oils. These seem to work best once again with a cut diaphragm.

As i say, my opinion.

Si

So with the cut bladders, the wheels will respond better to ripples in the surface etc?

In theory, indoors the shocks should be better suited with full bladders - on smooth surfaces etc, only jumps to land. But outdoors go to cut bladders? Would this make sense?.... or am I way off the mark.

generally, if you have rebound in your shocks its a bit like running a stiffer spring, the rebound is working with the spring.

suck is working against the spring. so the car feels softer

rebound or suck is not linear along the shock compression.

Hi Chris

Thanks for the reply, I think im correct in assuming that you are running a different setup to Mossy then for Worksop ?
Are you still using the front diff with the one way layshaft ?

Im building/setting up Chris Lovely`s CAT SX for him ( he got Schumacher sponsorship ) and wish to get it as perfect as i can for Rd2.

Mossy`s setup as quoted below..........

Im also unsure as to what the bold part means. Are these the std gears as come with the kit ?

The rest of your info is as i assumed - much apreciated mate :)

Hey Rich,
My differences are - I am running the rear diff high, this is to decrease driveshaft plunge and should increase traction, also it effects shock pack at speed.

My layshaft pulley is rolling. I find the one way diff is ultimately faster but a little harder to drive, I am aiming to make my car as forgiving as it can be while feeling positive and 'pushable'.

The internal ratio 36 tooth, thats the pulley on the opposite side of the spur layshaft which reverses the drive of the motor so everything spins in the right direction. You need to change both gears at the same time so they mesh, if you have a manual (I don't here, at work), the stock internal ratio is the middle one of the 3 available looking in the last few pages of the manual. Mine is stock, will be leaving it at that - mainly because too many variables bifuddullz me.

Chris

I actually ran a 34 tooth pulley at Worksop. I had the 36 one on my 4/2 car, sorry.

Si

I ran a 5.5 at Worksop. I did tell Jimmy this when he asked me so we can blame him lol. As for the metal pulleys, cant say as im not sure on what Schumacher are out of.

Si

Thanks again for a comprehensive reply Chris - understood :)

The whole "shock setup" thing is quite extensive, and there are many potential variables - more on these than others.

Back to Cd's point about a hole behind a bladder - in theory i'd agree, however, in practice - let's just say that was mk1 top caps, and i only ran them twice before i had some blocked up!

When you cut the bladder, you are effectively making yourself an AE style shock, although this does depend on how you build them. You can still build them with differing pressures.

I have run the shocks with the bladder cut, and no internal pressure all year. There have even built them with a little "suction" in a Losi style, and that does help on the smaller faster bumps. However, it does have some negatives, which can differ depending on how you like your car to feel.

In recent times i have been playing around with this more, and have actually switched to running a bladder on a few occasions, and Nathan W ran a bladder at Eastrax F2's.

As for ratios, i've been running what turned out to be kit for quite some time, and have been quite happy with how the power feels.