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Old 05-01-2013, 02:59 PM   #3376
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The shocktowers are currently in stock and sold through the following site:

http://www.capricornrc.nl/dsmotorsport/shocktowers
30 Euro to ship to NZ...
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Old 05-01-2013, 03:34 PM   #3377
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Originally Posted by JanE View Post
On pretty much each car out there HPI and yokomo springs work great. I have tested these showtowers with hpi springs and found the car to be much nicer. The fastest laptimes didnt go down much but we were able to drive the times much more consistant and improve over the entire run. Low profile shocktowers are a new trend but every other brand remains with the use of normal springs. Simply because those springs work.. if u look at the start of this thread everyone asked and tried if normal springs would fit. Because those springs are working good for years now.. and u cant just copy a spring rate when the spring is shorter. there are to many factors like wich spring steel or thickness of the wire etc.. to duplicate. With the option to just only run short xray forces people to just only buy their products. And from a business point of view one could see why offcourse. But nothing beats racers in trying to improve to get the most out of their cars.

The total length of the shock is about 1mm longer.
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Originally Posted by CristianTabush View Post
This is not totally true. The length of a spring has absolutely zero to do with the rate. All that matters is wire diameter, diameter of spring, number of coils and pitch.
I thought what he was trying to say is that you can copy the rate, but it doesn't mean it'll feel the same on track. That is, you can't just copy the rate.

-Mike
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Old 05-01-2013, 03:35 PM   #3378
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Originally Posted by edhchoe View Post
Unless the short spring comes to full compression while the longer one doesn't.

1) Is full compression necessarily when the coils touch?
2) Does the spring rate stay constant from zero travel to touching coils?
3) If the answer is no then the length of the spring may have an effect on the performance.
1) Surely full compression is when all the coils have touched and no more movement is available.

2) It should do if it's designed to be a linear spring.

3) Answered by the other two

I haven't come across any TC shocks yet where when the piston is fully in, the springs coils are touching. At most you compress the spring across maybe half it's full range.

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Old 05-01-2013, 03:39 PM   #3379
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Originally Posted by grippgoat View Post
I thought what he was trying to say is that you can copy the rate, but it doesn't mean it'll feel the same on track. That is, you can't just copy the rate.

-Mike
I don't understand how when a rate is copied it won't feel the same (when both springs are linear) provided they are designed to have the same rate across their usable range and both fit the shock properly.

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Old 05-01-2013, 05:27 PM   #3380
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So is having these shock towers a must?
Or do having xray short springs cover all tuning possibilities?
( 2.3-2.6, 2.5-2.8, 2.3,2.5,2.7.2.9) think that's all of them and I'm not positive about the #'s of the progressives but its close
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Old 05-01-2013, 05:43 PM   #3381
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Originally Posted by Skiddins View Post
I don't understand how when a rate is copied it won't feel the same (when both springs are linear) provided they are designed to have the same rate across their usable range and both fit the shock properly.

Skiddins
What does copying the rate mean, though? From my limited experience, I do know that springs with the same published rate from different manufacturers don't always feel the same on track. If you copy length/diameter/wire size/coil count, it'll probably be close (Spec-R 2.7 vs HPI Silver, for example). But you can't do that if you change the length, so you have to compensate with other factors and may still end up with a spring that doesn't quite feel the same. I haven't tried enough springs to know if two springs that are the same rate on Reflex's spring chart will actually feel the same.

Anyway, I'm sure Cristian is right, he always is. It just seemed like he might have mis-read what the other guy was saying, that's all.

-Mike
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Old 05-01-2013, 06:03 PM   #3382
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Basically, there are different ways to make a spring rate. For example:

RSD green springs are lets say nominal 15.0lb
RSD silver springs are nominal 15.0lb

Rsd green is a 1.4mm wire times x active coils
Rsd silver is a 1.5mm wirw times n active coils

The springs are the same rate, but have different qualities. They are "technically a different spring."

The spring rate can be changed by using a different diameter wire and a different id or different number of coils.

However, if I take either one of the springs and change the length, the rate remains constant. A 22 mm green spring will still be a 15.0 lb spring, and a 30mm green spring will still be a 15lb spring and so on.

Length is the only thing that does not affect the rate of the spring. The only limitation of a shorter spring is that the coils are so close together that if compressed too far they can start touching quicker, making the spring act progressive like our asphalt progressive springs.

Progressive springs are a fantastic tuning option on the T4 though. The chassis has a very low CG, and the progressive spring allows the car to roll more early on in the corner. This provides better entry steering. As the car collapses the spring, the spring acts stiffer, giving the car more middle and exit steering as it is able to maintain a more constant pressure on the tire. In the rear, the car gains more rear bite as the chassis rolls.

On cars with taller cg's the benefit is not as marked because the car will tend to dump to early and then gain more steering from the rate getting stiffer. This can make the car hard to drive, but can be valuable on lower grip situations.

I don't really like running anything else than our progressive springs on the T4 on asphalt anymore, but I understand if people don't always like the feel of it. The car reacts much faster and not everyone can benefit from a quicker reacting car.
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Old 05-01-2013, 06:18 PM   #3383
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Quote:
Originally Posted by grippgoat View Post
What does copying the rate mean, though? From my limited experience, I do know that springs with the same published rate from different manufacturers don't always feel the same on track. If you copy length/diameter/wire size/coil count, it'll probably be close (Spec-R 2.7 vs HPI Silver, for example). But you can't do that if you change the length, so you have to compensate with other factors and may still end up with a spring that doesn't quite feel the same. I haven't tried enough springs to know if two springs that are the same rate on Reflex's spring chart will actually feel the same.

Anyway, I'm sure Cristian is right, he always is. It just seemed like he might have mis-read what the other guy was saying, that's all.

-Mike
The problem with published rates for springs is that they are never accurate, that's why so many springs that are rated the same actually feel different.
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Old 05-01-2013, 06:35 PM   #3384
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Quote:
Originally Posted by Skiddins View Post
1) Surely full compression is when all the coils have touched and no more movement is available.

2) It should do if it's designed to be a linear spring.

3) Answered by the other two

I haven't come across any TC shocks yet where when the piston is fully in, the springs coils are touching. At most you compress the spring across maybe half it's full range.

Skiddins
I see.
In that case the springs should behave the same as long as there is no preload when the shocks are off the car.
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Old 05-01-2013, 07:36 PM   #3385
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Originally Posted by CristianTabush View Post
Basically, there are different ways to make a spring rate. For example:

RSD green springs are lets say nominal 15.0lb
RSD silver springs are nominal 15.0lb

Rsd green is a 1.4mm wire times x active coils
Rsd silver is a 1.5mm wirw times n active coils

The springs are the same rate, but have different qualities. They are "technically a different spring."

The spring rate can be changed by using a different diameter wire and a different id or different number of coils.

However, if I take either one of the springs and change the length, the rate remains constant. A 22 mm green spring will still be a 15.0 lb spring, and a 30mm green spring will still be a 15lb spring and so on.

Length is the only thing that does not affect the rate of the spring. The only limitation of a shorter spring is that the coils are so close together that if compressed too far they can start touching quicker, making the spring act progressive like our asphalt progressive springs.
If you have the same wire diameter / active coil count / spring diameter, and you make the spring longer, the spring will have more wire, won't it? And that will make it softer? What if instead of keeping the active coil count the same, you keep the active wire length the same (i.e. slightly fewer active coils on the longer spring).

With the shorter spring, the first coil will have a shallower angle to the end coil. Wouldn't that cause it deactivate faster, and make the spring more progressive? Would that even be noticeable with the difference between a normal ~25mm spring and a T4 spring?

I might be imagining this, but... Does the angle of the wire (is that pitch?) affect the way the compression force is put into the wire? Like bending force vs. twisting force? Unless I'm mistaken, when you stretch out a spring, the inner diameter gets slightly smaller (or the spring uncoils slightly, or some combination of the two), and when you compress it, the opposite happens. Does the wire react to bending vs. twisting differently?

-Mike
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Old 05-01-2013, 09:21 PM   #3386
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Guys,

Two springs are the same only when their wire material, dimension, number of coils and total lentgh is the same. If you add one turn to the spring, it will be harder at a certain distance. For example, if you decide to measure a spring rate when the spring is compressed to 20mm lentgh (not compressed 20mm from initial state but to 20mm total lentgh), you need to compress the longer one more which will make it harder, less coils but same lenth makes it softer, thinner wire the same.

There is likely also a difference in how the manufacturers measure the spring rate, this giving two springs with the same specified rate made by two different manufacturers could be completetly different.

Providing that there is no standard in measuring spring rates for RC springs, there is likely not two similar springs around...

Below from Wikipeida:
As long as they are not stretched or compressed beyond their elastic limit, most springs obey Hooke's law, which states that the force with which the spring pushes back is linearly proportional to the distance from its equilibrium length:

F=- kx

where
x is the displacement vector – the distance and direction the spring is deformed from its equilibrium length.
F is the resulting force vector – the magnitude and direction of the restoring force the spring exerts
k is the rate, spring constant or force constant of the spring, a constant that depends on the spring's material and construction.
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Old 05-01-2013, 10:48 PM   #3387
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Originally Posted by grippgoat View Post
If you have the same wire diameter / active coil count / spring diameter, and you make the spring longer, the spring will have more wire, won't it? And that will make it softer? What if instead of keeping the active coil count the same, you keep the active wire length the same (i.e. slightly fewer active coils on the longer spring).

With the shorter spring, the first coil will have a shallower angle to the end coil. Wouldn't that cause it deactivate faster, and make the spring more progressive? Would that even be noticeable with the difference between a normal ~25mm spring and a T4 spring?

I might be imagining this, but... Does the angle of the wire (is that pitch?) affect the way the compression force is put into the wire? Like bending force vs. twisting force? Unless I'm mistaken, when you stretch out a spring, the inner diameter gets slightly smaller (or the spring uncoils slightly, or some combination of the two), and when you compress it, the opposite happens. Does the wire react to bending vs. twisting differently?

-Mike
This is only the case if the spring is compressed fully. But for most applications it is not.

The spring with the same wire diameter and coils, no matter the length will use the same amount of wire, it "travels" the same distance while being coiled the same number of times.

The difference is the ratio at which it compresses it has a shorter distance to compress fully, therefore the rate of change of the spring rate changes more rapidly. However the standing rate is the same.

I have the empirical data to back this up.

Basically all springa get stiffer as they compress. Short springs just get stiffer quicker. Hence the faster reaction time.
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Old 05-02-2013, 12:37 AM   #3388
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So then the spring rate is not constant throughout the compression range.
What good is the spring rate?
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Old 05-02-2013, 04:57 AM   #3389
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Like i said before , you cant just copy a spring rate and expect the same feeling. In my opinion when u take a short and a long spring the starting rate is the only thing u can make the same. But as the spring compresses the rate of a shorter spring will change more quickly vs a longer spring. And therefore will give a different feel on track.

In offroad kyosho have made some blue and orange springs. Doesnt matter what car u put them on, they nearly always work. The same with onroad and hpi springs, doesnt matter what car u put them on, they just work great in most conditions.

For me personal the HPI springs were THE springs for asphalt racing on the T3. So when i drove the T4 for the first times the car was ok , but i never have had the same dialed feeling on asphalt as i had with the T3. Most of all the steering didnt feel right. So after we had contact with DS motorsport he designed these shocktowers for us. So for me, its a improvement of the car as the silver hpi springs give me the same nice feel as they did on the T3. And like mentioned before, my fastest lap didnt go down by that much (u can drive the fastest lap with a crap car) but i could drive the faster times more consistant and longer during my run.

I have pretty much every short spring there is for the T4 and after some back to back testing , again for me , the car is much nicer with just normal springs.
Offcourse this is not something every t4 owner needs, but for those always look to improve or just simply still dont like the feel of the car with the short springs its a nice addition to have as option part.
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Old 05-02-2013, 06:59 AM   #3390
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Originally Posted by JanE View Post
Like i said before , you cant just copy a spring rate and expect the same feeling. In my opinion when u take a short and a long spring the starting rate is the only thing u can make the same. But as the spring compresses the rate of a shorter spring will change more quickly vs a longer spring. And therefore will give a different feel on track.

In offroad kyosho have made some blue and orange springs. Doesnt matter what car u put them on, they nearly always work. The same with onroad and hpi springs, doesnt matter what car u put them on, they just work great in most conditions.

For me personal the HPI springs were THE springs for asphalt racing on the T3. So when i drove the T4 for the first times the car was ok , but i never have had the same dialed feeling on asphalt as i had with the T3. Most of all the steering didnt feel right. So after we had contact with DS motorsport he designed these shocktowers for us. So for me, its a improvement of the car as the silver hpi springs give me the same nice feel as they did on the T3. And like mentioned before, my fastest lap didnt go down by that much (u can drive the fastest lap with a crap car) but i could drive the faster times more consistant and longer during my run.

I have pretty much every short spring there is for the T4 and after some back to back testing , again for me , the car is much nicer with just normal springs.
Offcourse this is not something every t4 owner needs, but for those always look to improve or just simply still dont like the feel of the car with the short springs its a nice addition to have as option part.
What ride height can you get with HPI springs and standard towers, shocks and shock bottoms?
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