hierog

iTrader: (6)

looks great Steevo!! where did you pick up the Square heatsink and the red 3 piece shaft?

vic

Steevo

Hi vic,
Got all the goodies from Andy at http://www.hobbymania.com.hk

I know that the Tech 3 piece shaft is now discontinued so it will be near Impossible to get unless someone has it in their shop currently.

The heat sink is the Square One and it is still available so send Andy an email and see what he can do for you

steevo

Barry White

Did anyone try to boil the pinions?

black-knight

yes, they needed more salt

Matteucci

Thanks guys for the set up help on carpet!
Mabucci

RCGaryK

iTrader: (3)

Ok, having never owned a shaft car, I gotta ask the question. Why does the Evo seem to have ring and pinion problems, while the Yokomo, Cuda, and TC3 don't? I don't even remember the Evo 1 or Evo 2 having these problems in the drive train

JusBox

iTrader: (1)

Just based on what I've read and seen, i think it's how the ring gear is supported. There's too much play and this results in the problems. Also, isn't is only supported by one bearing instead of two like many other shaft cars?

jeffreylin

I think Tamiya tried to decrease the pitch of the bevel and diff gears to increase efficiency and decrease fiction. While it worked as intended the compromise was the durability of the gears. Look at the size of gears on the Barracuda and you will see the difference. The Cuda is also a noisier car which suggests more friction in the drivetrain.

Atomix

iTrader: (1)

It has nothing to do with being supported by one bearing. All the cars people compare the evo to are 3 piece shaft cars. Fact is the 3 piece shaft needs two bearings at each end to keep the outdrive spinning true. Because the evo has a one piece shaft, this is not necessary, as the "straightness" of the shaft keeps it spinning true. The benefit is less drag in the drivetrain, at the cost of stripped gears & possible bent shafts in a big hit.

The reason the gear strips is simple. There is no float in the shaft mechanism at all.Simply put, when the car has a frontal impact, the chassis "shorthens, but the shaft doesnt as it hasnt got the "float" it needs to absorb the impact Subsequently, the gears mangle into each other on impact.

So how do you fix it?
With all due respect to those that have tried, some with simple, some with complex methods, the best way is still shimming. While I appreciate the effort & thought that went into the "pinning" idea, you would have to run the gearbox covers pretty loose so it doesnt bind as the pinion sits out too far on the shaft.

I have had the best results by pushing the pinions all the way back to the step on the shafts. Tighten the gearboxes so the screws "nip" up.Like shimming an armature, feel the float between gearboxes. Shim from the rear gearbox first & place a 5mm shim between the step on the shaft & the pinion gear. Tighten up & do the same to the front. I have found that generally speaking, 2 shims in the rear & 1 in the front is about right. This allows you to have a good mesh, tight gearbox covers & no binding. Traxas make teflon shims for those concerned with "freespin", which is a bit of a wank anyway.

Doing this minimises the damage from a front hit, not fixes it completely, nothing ever will. The Tech 3 piece shaft is loud, heavy & ugly. A oneway gear costs $2.50 usd. Have plenty of 'em.

If the gear goes, chances are that not only will you finish your race, but also your race meeting. Unless you dont hit ANYTHING during your remaining races, you wont suffer a performance disadvantage, but lets face it, if we didnt hit anything, we wouldnt have a stripped oneway gear .

Cobra81li200

With all respect, you're wrong on some points.

First of all, I saw one way gears break without any impact.

Second, the reasons are multiple.

One is the fact that the gear bends under load. Indeed, compare the strength between the one way gear and the diff gear and you'll notice that the diff gear is much stronger than the one way. This is for two reasons, the first being the material (the diff gear appears to be made of a graphite material and the one way of a standard plastic). The second reason is the thickness of material behind the gears (the diff gear is much thicker). This combined with the design of the one way results in the fact that the gear bends under high loads (being an impact or a high end motor).

Another one is the fact that the material of the gear box is weak. Indeed, after a number of runs the sitting for the bearing have some play. Look at what BigDog have done in his mod : you would never have been able to use a ring like that in a TC3 or a SD. This is (with the added trength that it provides) one of the reasons why the square gear boxes partly fixes the problem.

Again, shimming is important on ANY shaft driven car. there must be a little play, but just enough so that there is no bending.

About the modulus of the gear, this is totally wrong, the modulus is exactly the same as with a TC3 and a SD (and I guess a Pro 4). Proof is the fact that TC3 gears are used by some drivers with success (and this also proves that the weakness of the gear itself is the real problem).

Another thing, such a long shaft can only vibrate at high rotating speed. Indeed, there is no "straightness" possible in a shaft, it can only be bent even if you cannot see it. In my opinion, the bearing in the cross plastic part behind the steering is necessary, if not indispensable.

Also, another big fault is that the bevel gear should be secured on the shaft and it is not.

These are all the reasons why there are so many breakages. Not all are involved on each car, but at least one or two.

To solve the problem, a modification on the one way is a MUST have. Larger back plate or modified one way (with inverted and bigger plate like the Jurgen one way has) are the possibilities.

Shimming each gear box SEPARATELY (I mean shim the first one, take the shims out, shim the second one and then put the shims for the first one back) is also necessary in any case.

Make sure there is no play in your bearing if there is, then replace the gear box or use BigDog's tip. About the gear boxes, Surikarn used a graphite gear box that was produced only for TRF drivers and provides less breakages.

Put a bearing in the cross part behind the steering (secure it with a dot of glue).

Pin the bevel gear like BigDog did (very good tip, good job !).

V12

iTrader: (1)

Cobra is right in every point he posted.

Shimming is a must with every shaft car but itīs very easy if youīre using the Square gearbox as every unit is made the same.

Also the additional bearing in the A8 plastic part is a must and if youīre using the Jürgen oneway you wonīt experience any trouble again with the oneway gears.
I didnīt believe in the rumours about this oneway in the beginning but now I have lotīs of spare gears laying around as I never needed any new one after this mod. The same I heard from every other driver using this oneway.

But from what I have heard here some people also have problems with the SDīs oneway gear.

There were also some other little problems with the EVO3 I had fixed in the meantime but there is one problem I didnīt find a solution until now.
Itīs the duration of the diff. I donīt have the problem the diff is melting or anything like that. But after a very short time the diff feels gritty. I have to rebuild the diff after 5 - 10 runs.
I never had this with the TC3 or the XXX-S. Usually their diffs lasted about 3 month, donīt know how much runs this is.
I tried different diff greases the white diff halves and the carbide diffballs. But nothing changes. The original Tamiya diff grease works best for me but nothing more than 10 runs.
I think either the diffrings are too soft or the thrust bearing is worse than the TC3 or the Losi ones. Any solutions for this?

BigDogRacing

iTrader: (12)

Cobra- thak you and thanks for teh very intelligent description of the problem.

Atomix- you are right about the other cars being 3 piece shafts, but wrong about what the problem is... you say the solid shaft car keeps the drivetrain running true but that's where you are wrong. In fact, the reason Tamiya purposly incorporateld "float" into the pinion bearings in the front and rear transmissions is because there will always be some runout in the shaft and therefore something must give to keep from binding. This "floating bearing" is THE NUMBER ONE REASON for the teeth stripping on the ring gears and pinions. The next worst (excuse poor grammar) problem is the fact that the shaft does NOT fully engage the FRONT pinion (bevel) gear and even if it did, the horrendously long bevel on the front of the shaft allows the pinion to kick sideways (deflect is the technical term) and bind up. Both of these faults cause the lash between the pinion and ring gear to open up under any strain and we all know that the less the teeth engage each other the more chance there is of breaking them.

You can take the car to any good engineer or machinist and explain the problem and they will tell you that I'm correct. We thought the shaft was coming forward at first like you do, but found that isn't the problem. If you do the simple and cheap fix like I showed along with using a decent backing plate for the oneway gear (the third problem on the list of faults) then you won't have any more problems and you can shim your drivetrain correctly to be free and fast. Or you can keep replacing gears and take a chance on it costing you the state race in 19 turn sedan becasue your good friend got turned sideways in the first turn and you hit him square which cocked your pinion gear into a bind in the transmission and your car was so slow with the binded gear and chewed up ring gear that it wouldn't pull a greasy string out of a cat's butt... Of course that's just a theoretical situation...

BigDogRacing

iTrader: (12)

V12- mine has stayed prety smooth for a while, and it's better with good bals like the ones from Acer or rc4less, but I know exactly what you mean. I honestly believe it's the thrust bearing and I've been meaning to mic the I.D. and O.D. of the thrust bearing races to see if another manufacturer's rings will fit, but even if I do that, I don't have access to many different thrust bearing rings.

*****Is there anyone here that works at a well stocked hobby shop? If you do I'll give you the measurements and you can try to find us some that might fit.

I believe regular 2.0 or 2.5mm balls will work fine. Acer has 2.0mm balls.

Oh, V12- I tried the Tamiya grease and it's good, but I still like the Stealth grease better.

V12

iTrader: (1)

BigDog
What grease are you using for the thrust bearing? The Stealth Black grease?
I was using the Stealth grease or the Associated red label grease (thicker) for every car before but for any reason it doesnīt work for me with the EVO3 diff. But donīt know why.

Regarding the thrust bearing I will look for the old Yokomo YR-4 thrust bearing as these had the same 2mm diff screw. Maybe this will fit. Donīt know if the SD have the same diff screw diameter.

As diffballs Iīm using the Tamiya carbide now but I have to say it doesnīt make any difference to the kitīs ball. Usually the carbide will make a smoother and longer lasting diff with every other car but again it doesnīt work here any better.

Atomix

iTrader: (1)

Its nice to have a discussion that isnt based on flaming
Very rare indeed

I have found by getting the pinions as far back on the shaft as possible & getting the gearbox covers as tight as possible it allows the bearing to sit in the housing more "consistently".

The mesh of the gears shouldnt be left up to the gearcovers tightness. If the diffs dropped in vertically, this would not be an issue, sadly, they dont.........

Cheers