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Old 04-29-2011, 12:39 AM   #1
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Questions?? On-road car dictionary

Hi,

I'm new here on this forum and to RC in general..

One of the things that trouble me, is the fact that when I read through all the great post here I'm constantly frustrated because I don't know what you guys are talking about.

Half of it probably stems from the fact that I'm danish, and the other half is my total lack of knowledge regarding rc's ;-).

I was hoping to help this with a dictionary containing explanations on different words and abbreviations used in the world of RC cars.

I'll kick it off with an explanation on what "ECS" means.

Equalized Corner Speed (ECS)

There is a website on the Xray site that explains it but I'm not allowed to link to it, so I'll try and explain it my self.

It is a new driveshaft for the front wheels. Normally there is only one joint to let the front wheels steer, but still turn...
The big deal with ECS, as far as I can tell, is that there now are two joints instead of one on the shaft, making the bending of the shaft more subtle, than if it were to bend in just on place, thus creating less vibration on the inside wheel while cornering.

as far as I can tell this thing is Xray specific, not sure if other manufacturers have a similar product.


I was hoping that some of you more experienced drivers out there would want to share your knowledge with the rest of us.

No topic is to simple, believe me, I at least, need all the help I can get ;-).

Here are some things I would like to see explained, f.ex

What is a sway-bar and what does I do?
What is droop, and how does it affect the car?
What is a spool, something to do with the differential?


There a tons of questions I would like to see answered, and I think that I'm not alone here.


If this thread should have been placed in the rookie section, I would appreciate if one of the moderators would kindly move it for me.



With regards

Anders Risager
A proud but almost clueless owner of two great, cheap used onroad cars

The Xray T2'008
&
The Losi XXX-S Sport

Last edited by Coach-Z; 04-29-2011 at 05:59 AM.
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Old 04-29-2011, 07:54 AM   #2
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Default Hudy's T2 Setup Book

Quote:
Originally Posted by Coach-Z View Post

Here are some things I would like to see explained, f.ex

What is a sway-bar and what does I do?
What is droop, and how does it affect the car?
What is a spool, something to do with the differential?


With regards

Anders Risager
A proud but almost clueless owner of two great, cheap used onroad cars

The Xray T2'008
&
The Losi XXX-S Sport
Just about everything you might want to know is in here...

http://www.rcring.gr/files/Manuals/T...tupbook_v2.pdf
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Old 04-29-2011, 08:09 AM   #3
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http://www.google.com/url?sa=t&sourc...9V6KEKX79BfBhg
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Old 04-29-2011, 08:16 AM   #4
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Quote:
Originally Posted by Coach-Z View Post
as far as I can tell this thing is Xray specific, not sure if other manufacturers have a similar product.
Actually, double cardan joint driveshafts were first seen on Losi's JRX-S TC.
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Old 04-29-2011, 08:26 AM   #5
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Quote:
Originally Posted by Coach-Z View Post

[...]

I'll kick it off with an explanation on what "ECS" means.

Equalized Corner Speed (ECS)

There is a website on the Xray site that explains it but I'm not allowed to link to it, so I'll try and explain it my self.

It is a new driveshaft for the front wheels. Normally there is only one joint to let the front wheels steer, but still turn...
The big deal with ECS, as far as I can tell, is that there now are two joints instead of one on the shaft, making the bending of the shaft more subtle, than if it were to bend in just on place, thus creating less vibration on the inside wheel while cornering.

as far as I can tell this thing is Xray specific, not sure if other manufacturers have a similar product.

[...]
That's not how ECS driveshafts work. In reality they're nothing else but CV driveshafts (CV=constant velocity) but such is the generation Y world, everything has to have some incoprehensible acronym today to attract their attention to repackaged old technology. Xray is good at this and optimising too.

The problem with the single universal joints is that when the shaft goes through a rotation, the axle (the other shaft if you will) does not rotate around the same arc (because the cross in the joint is at 90 degrees - CROSS joint, get it?) therefore putting a small stress on the joint. As the rotation continues, the axle "catches up" and compensates for this small difference, so after a complete rotation both shafts have done 360 degrees, but rotational speed is different on sections of this complete revolution. The double jointed shafts compensate for this because the second joint (or uni if you will) returns the point where torque is applied to the driven shaft at 0 degrees to the input shaft.

Imagine you have a piece of string with a weight at the end and you spin it in the air, standing in front of a wall with a source of light behind you. The shadow of your weight on the wall will be a circle. If you move sideways, the shadow changes into some sort of ellipse. This elipse does not have the same circumference as the circle that was there before, so the shadow of your weight must travel at a different speed to the weight at the end of your rope to cover a different length trajectory. The truth is that the shadow speeds up and slows down and you will be able to see this in the shadow. In total, the shadow takes the same time to do a full lap of its trajectory, just as your weight does, but the shadow doesn't go at constant speed. That's what happens with a uni joint, where your weight is one arm of the cross joint and the shadow is the other arm (which in corners does no longer go on a circular trajectory as viewed from the input shaft). The angular speed of the two is the same, but equal angles do not divide an elipse in equal lengths on the circumference as they do with a circle. That's where the problem comes from. Using two cross joints overcomes this problem as the difference introduced by the first joint is cancelled by the second.

Hopefully this makes some sense.

There is a website where you can just plug in these questions:

http://www.howstuffworks.com/

Most companies offer ECS driveshafts these days.

Try it.
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Last edited by niznai; 04-29-2011 at 08:51 AM.
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Old 04-29-2011, 01:08 PM   #6
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Wow, get home from work and look at all this great response from you guys


Really appreciate it, that setup book for the T2 explains it all...


Does something similar exist for the Losi XXX-S Sport?
I have one of those as well...
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Old 04-29-2011, 02:34 PM   #7
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Quote:
Originally Posted by Coach-Z View Post
Wow, get home from work and look at all this great response from you guys


Really appreciate it, that setup book for the T2 explains it all...


Does something similar exist for the Losi XXX-S Sport?
I have one of those as well...
The "xxxmain" or "mPowered racing" Touring Car Chassis Setup Guide written by Martin Crisp is a very handy resource for any touring car. I don't know if there is an electronic version of it though. I have a printed copy. I also see Martin at the track all the time, so I often just ask him setup questions directly.
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Old 05-04-2011, 12:20 AM   #8
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Originally Posted by niznai View Post
That's not how ECS driveshafts work. In reality they're nothing else but CV driveshafts (CV=constant velocity) but such is the generation Y world, everything has to have some incoprehensible acronym today to attract their attention to repackaged old technology. Xray is good at this and optimising too.

The problem with the single universal joints is that when the shaft goes through a rotation, the axle (the other shaft if you will) does not rotate around the same arc (because the cross in the joint is at 90 degrees - CROSS joint, get it?) therefore putting a small stress on the joint. As the rotation continues, the axle "catches up" and compensates for this small difference, so after a complete rotation both shafts have done 360 degrees, but rotational speed is different on sections of this complete revolution. The double jointed shafts compensate for this because the second joint (or uni if you will) returns the point where torque is applied to the driven shaft at 0 degrees to the input shaft.

Imagine you have a piece of string with a weight at the end and you spin it in the air, standing in front of a wall with a source of light behind you. The shadow of your weight on the wall will be a circle. If you move sideways, the shadow changes into some sort of ellipse. This elipse does not have the same circumference as the circle that was there before, so the shadow of your weight must travel at a different speed to the weight at the end of your rope to cover a different length trajectory. The truth is that the shadow speeds up and slows down and you will be able to see this in the shadow. In total, the shadow takes the same time to do a full lap of its trajectory, just as your weight does, but the shadow doesn't go at constant speed. That's what happens with a uni joint, where your weight is one arm of the cross joint and the shadow is the other arm (which in corners does no longer go on a circular trajectory as viewed from the input shaft). The angular speed of the two is the same, but equal angles do not divide an elipse in equal lengths on the circumference as they do with a circle. That's where the problem comes from. Using two cross joints overcomes this problem as the difference introduced by the first joint is cancelled by the second.

Hopefully this makes some sense.

There is a website where you can just plug in these questions:

"howstuffworks"

Most companies offer ECS driveshafts these days.

Try it.
Had to read this a couple of times, but I think I get it now...

If I understand you correctly the reason you get that wobble in the wheels when turning, is because of the of the change in speed in the axle as it goes from the top of arc on the elipse to the more "straight' part, thus changing speed.

Did I understand it correctly?
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Old 05-04-2011, 05:37 AM   #9
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Anders, it might surprise you that more of us DON'T know what all those terms are vs. those that do. Keep in mind that some of it involves marketing and promotions. In other words....fancy new terms sound cool. The other part relates to actual new technology. And quite a bit of that is better understood by drivers with skills able to use it. Most of us mere mortals are happy just to learn the finer points of suspension setup.
Regarding the XXX-S. There isn't anything specific to it that I know of BUT one of the best things I've ever read about suspension tuning is here: http://www.stranahan-rc.com/corneringatthelimit.html.

John also has a thread on rctech that provided me with loads of great info and he is quite frank in his belief that the X is one of the best cars ever made.
http://www.rctech.net/forum/electric...n-mod-etc.html
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