TRF415boy

I didn't dare saying this, but i think this is perfectly true.

rtypec

iTrader: (2)

Okay...just wondering, because chatter is bad Don't want our cars sounding like a moaning badger when it corners

Raycer

Could you write a bit more detals on how to...tks

TRF415boy

As has previously been said, chatter is mainly created by the CVD joints, and is a part of the design of the driveshafts. There is no way to get totally rid of it, you may not always hear it, but it's always here. Unless a real CVD design comes out.

rtypec

iTrader: (2)

Here is a theory. Please correct me if I'm wrong or if you think I've been smoking crack

When a universal joint is fully deflected and rotated (wheels turned while cornering) it will bind at two points during the course of one revolution. When using a spool with inline outdrive slots, the universals' bind spots will be in phase and the additive bind can cause a "chatter" of twice the magnitude. You'll notice some spool-equiped cars that chatter excessively,while cornering, will exhibit some form of understeer. This is because the front tires struggle (and wheel hop?) for grip as the universals bind simultaneously. On a spool with outdrive slots that are 90 degrees from each other, the universals will pass through their bind spots at different times. The chatter will still be there, but its magnitude will be decreased, allowing for a slightly more consistent feel. It's a small but noticeable difference.

Turbonium

iTrader: (27)

Rod, not sure about the crack thing, but sounds plausible....

seems like its kind of like a driveshaft in, say, a car or pickup... usually they are offset, mainly to reduce vibration, and give better balance.

linger

iTrader: (1)

Rod is right on the money.

Actually, the RC universal design changes velocity 4 times per revolution. Putting the dogbones at 90 deg puts things slightly out of phase.

If you look at the driveshft of a 1:1 truck, you will notice that the universals on the opposite ends of the driveshaft are always 90deg relative to each other.

linger

iTrader: (1)

Here's a webby that explains it a bit more...though not completely representative of our application.

http://www.sdp-si.com/D200/PDF/D200_T59.pdf

TRF415boy

Well, this explains exactly the contrary. It says the joints shouldn't be turned 90° which makes perfect sense to me. Besides, this is only true when the wo angles are the same, and it doesn't apply in the case of a spool.

Maybe it's time to explain what happens in a driveshaft, as i see some things said here are quite wrong.

First things first, the angular velocity does NOT change 4 times per rev. It changes all the time, as the angular velocity follow a sinusoidal law (as can be seen in that PDF file by the way). What changes 2 times per rev is the fact that the driveshaft accelerates or decelerates, and that can also be see on that same diagram (it's when the curve crosses the 0 variation of angular velocity line).

Now that constant change in speed, combined with the weight (and thus inertia) of the wheels, is what creates chatter. If you put your car with all 4 wheels in the air, give a bit of throttle and steer very little (let's say 20 to 50% steering), you'll hear it (especially if you have a spool). Try doing the same without tyres, you won't hear anything.

That's it for chatter caused by the CVD joints. You can notice here the coupling with the spool has absolutely no effect whatsoever.

Now about what Rod Explained concerning the CVD's having hard spots, it only occurs when you steer a lot (more than 60% to full lock approximately). It's an issue mainly caused by the fact that the CVD is being used at an angle it shouldn't be. And if you notice, new CVD's are much smoother than used ones. Now, this hard spot occurs 4 times per rev, and having the left and right cvd's 90° off angle won't change anything, the hard spots will still occur at the same time, as I may remind you that 90° is 1/4 of rev. What will happen though, is that the CVD joints will work off balanced, meaning one wheel will accelerate whilst the other will decelerate, which is an undesired effect if you ask me.

Hope things are cleared now

Eirik

This is not a problem with the Tamiya shafts anyway as they have 4 holes so you can build them 90deg relative to each other no mather what the spool looks like.....

Received my RC Maniax spool today and it looks outstandig!! Very light weight and the finish is top of the line!!

Will test it this weekend and see how it goes!!

Old CVD's will chatter more than new ones, so it's important that the CVD's are in good shape when a spool is used.
It also helps to grease the outdrives and CVD's with a thick grease like the "Tamiya Anti Wear Grease" etc.

TRF415boy

Couldn't say it better myself...

rtypec

iTrader: (2)

Hey Eirik. Jimmy Jacobson introduced me to this stuff called Mugen Super Joint Grease. His car is virtually silent in the corners...and that's with a 90degree spool. He also added a spacer on the steering knuckle to reduce throw. I tried it and suffice to say, I have some on order. Of course, the joints will require a little more maintenance as this stuff is pretty light, but it may be well worth it

Eirik

Hello rtypec,

Thanks for the tips!!

I have tried that and it works really good, but get trown off pretty fast as it's very light like you said.....

I got some grease called "Spin Grease" this is really good stuff!! Best grease I have tried so far and it's a bit thicker than the Mugen grease so that it will stay where you put it. Rainbow10 has it in stock.....

I have also had excelent result with "Valvoline MP Grease" as well...!

rtypec

iTrader: (2)

As clear as mud j/k. Nice explanation. Right or wrong, I just wanna drive my car. I hope we can agree on that.

MDawson

iTrader: (27)

I have had no problems with spools or chattering.

Below is the washer install on the spindle. Set your steering end points. Use Loctite ViperLube on the dogbone pins and spool and you will be all set.



As for spool quality and wear, I have over 25 runs on the new spools from SpeedTech with no wear problems at all. Durability has not been and issue and yes, I do run the cvds offset or timed.

That running 6/7T motors at Tamiya USA.