Kagama Lee Spring Servo Saver Spring - What you need to know

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Stock spring
Horatio said:
However, what would be a crude test, is to compress the springs on a bathroom scale with a clamp. You can see exactly how many kg's it takes to compress the springs that you have in your possession.

In the case of the Lee Spring - it's 19mm high and is Solid at 9mm, fully compressed. It takes 2kg per mm to compress it, so given that it's a linear compression spring, we can expect 20kg to fully compress the spring. Between a finger and thumb, that exceeds what is humanly possible. The stock spring in comparison is certainly possible to compress (almost completely) between finger and thumb.
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Stock spring: About 25lbs

Aliexpress spring (Mn65): About 40lbs

Lee spring: A little over 50lbs

So yes the aliexpress spring is a happy medium.

Also they are kind of fibbing about the length out of the bag it's 25mm long for these "20mm" springs, OD is about 17.6mm which is acceptable tolerance. Grinding the ends with a sanding wheel and a drill press and fuly compressing it once reduced it to about 21.5 long uncompressed (it looses a few mm after an initial full compression). Maybe this is the estimated lenght after processing the raw springs? I just chucked up a dremel sanding wheel and held the spring in a flat surface and lowered it onto the end (need to have a container of water nearby to dunk it in every 5 or so to cool it). It has the same number of turns as the stock spring and the lee spring so the amount of servo saver deflection should be unchanged but you will need to compress it more to get the nut started on the thread. It is easier to tighten than the lee spring is but I still don't see it backing off.

EDIT after grinding the ends I inserted a rod into the spring to lift up the end of the wire and then carefully rounded it off with a dremel because I am OCD like that
 
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Atomic Skull said:
Stock spring

Stock spring: About 25lbs

Aliexpress spring (Mn65): About 40lbs

Lee spring: A little over 50lbs

So yes the aliexpress spring is a happy medium.

Also they are kind of fibbing about the length out of the bag it's 25mm long for these "25mm", OD is about 17.6mm which is acceptable tolerance. Fully compressing and grinding the ends with a sanding wheel and a drill press reduced it to about 21.5 long. Maybe this is the estimated lenght after processing the raw springs? I just chucked up a dremel sanding wheel and held the spring in a flat surface and lowered it onto the end (need to have a container of water nearby to dunk it in every 5 or so to cool it). It has the same number of turns as the stock spring and the lee spring so the amount of servo saver deflection should be unchanged but you will need to compress it more to get the nut started on the thread. It is easier to tighten than the lee spring is but I still don't see it backing off.

EDIT after grinding the ends I inserted a rod into the spring to lift up the end of the wire and then carefully rounded it off with a dremel because I am OCD like that
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Nice one! This post takes all the guess work out of things. 👍👌
 
Ok so I just discovered that even if an aluminum servo saver arm is perfectly clean and smooth it still might as well be locked with a hard spring installed. It seems that the aluminum on plastic mating surfaces have a LOT more stiction (static friction) than plastic on plastic. Even the stock spring was harder to move with an aluminum servo saver arm installed than with a plastic one.
 
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Atomic Skull said:
Ok so I just discovered that even if an aluminum servo saver arm is perfectly clean and smooth it still might as well be locked with a hard spring installed. It seems that the aluminum on plastic mating surfaces have a LOT more stiction (static friction) than plastic on plastic. Even the stock spring was harder to move with an aluminum servo saver arm installed than with a plastic one.
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Interesting. The nylon composite have some degree of self lubricating properties, but I suppose the combination of the 2 different materials - 1 of them not self lubricating - held together under a load changes the whole dynamic of the cam.

The coefficient of friction between nylon and alloy is 0.20 to 0.30 (dry)
The coefficient of friction between nylon and nylon is 0.15 - 0.25 (dry).

Ff = μ N

N being the Normal force between mating surfaces is often calculated from the weight of a material and the acceleration of gravity. For a cam with a spring - as you mentioned in an earlier post - this would be different again, but from the coefficients above we can quickly build the picture that the Alloy/Nylon cam may have up to twice the friction of a nylon/nylon cam, based on being clean and dry.

I suppose if the alloy gets dirty, worn or pitted for any reason - possibly corroded even - this could increase the friction even more.

For reference, the coefficient of friction between Rubber and Asphalt (dry) is 0.9

My 1/10th rigs do away with servo savers all together. If you crash, the servo fends for itself. 🤞
 
I'm going to try the Aliexpress spring with the aluminum arm the 55kg-cm steering servo is just barely able to overcome it which seems ideal. I also squirted some dry lube in between the two halves. The ADU racing aluminum servo saver arm combined with the lee spring might as well be glued together even though the two surfaces are pristine.

These springs can rust, I'm also going to look at the possibility of covering them in two part equipment paint. The lower OD tolerance allows for paint without it interfering.

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It wouldn't fit inside the cam so forget that, it was late wasn't thinking.
 
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I had the same issue with the aluminum on nylon (or is it plastic?) servo saver in a stock kagama LE. Even the stock spring provides no servo saving action in one direction and killed two servos. Once it gets roughed up with dirt, it binds up. Nylon on nylon with an upgraded spring works best and has over 50 runs in both of my corallys.

I tried dry lube but it quickly works its way out. Even so, it won’t protect the aluminum from dirt, which is what I think destroyed the aluminum.

IMG_0384.webp
 
Atomic Skull said:
Stock spring

Stock spring: About 25lbs

Aliexpress spring (Mn65): About 40lbs

Lee spring: A little over 50lbs

So yes the aliexpress spring is a happy medium.

Also they are kind of fibbing about the length out of the bag it's 25mm long for these "20mm" springs, OD is about 17.6mm which is acceptable tolerance. Grinding the ends with a sanding wheel and a drill press and fuly compressing it once reduced it to about 21.5 long uncompressed (it looses a few mm after an initial full compression). Maybe this is the estimated lenght after processing the raw springs? I just chucked up a dremel sanding wheel and held the spring in a flat surface and lowered it onto the end (need to have a container of water nearby to dunk it in every 5 or so to cool it). It has the same number of turns as the stock spring and the lee spring so the amount of servo saver deflection should be unchanged but you will need to compress it more to get the nut started on the thread. It is easier to tighten than the lee spring is but I still don't see it backing off.

EDIT after grinding the ends I inserted a rod into the spring to lift up the end of the wire and then carefully rounded it off with a dremel because I am OCD like that
Click to expand...
Nice work, good to have the info on all springs now. But in terms of bang for buck & the fact they bit easier for anyone to order the AliExpress spring takes the win I think. Your all welcome my gamble turned out to be a winner 😜
 
The cam needs to be sealed then, if dirt is a problem for aluminum it'll be a problem eventually for nylon as well. EDIT: Actually it depends on what kind of dirt fine particles will just polish it but sand is going to chew it up.

Nice work, good to have the info on all springs now. But in terms of bang for buck & the fact they bit easier for anyone to order the AliExpress spring takes the win I think. Your all welcome my gamble turned out to be a winner 😜
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For 1/10 vehicles and the Shiroi and Spark I think the aliexpress spring will do fine but I'd want the lee spring for 1/8 vehicles with large tires. Asuga depends on what tires you are using if you are using the stock buggy tires the aliexpres spring will probably work alright but if you are using wider/larger tires you probably want the lee spring. EDIT I forgot to mention that I have a Shiroi and it's currently using a stock spring as shipped, I haven't had the front end apart yet to get at it. Control isn't nearly as unresponsive as it was with the stock spring in the Asuga. This may simply be because you can't take a turn at high speed as sharply as with a buggy without rolling it.
 
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In the meantime, I tried to do a little race with the stock spring with a friend of mine who has the Talion, and as you can see in the video, the Shogun unfortunately turns too wide.
I can't wait for the AliExpress spring to arrive.
 
Let me clarify, I ordered the spring on AliExpress with these specifications: 2 mm wire, 20 mm length, 18 mm outer diameter. Instead, you're telling me it comes with a length of 25 mm and an outer diameter of 17.6 mm. Should I shorten the spring by 5 mm?
 
Opua said:
Let me clarify, I ordered the spring on AliExpress with these specifications: 2 mm wire, 20 mm length, 18 mm outer diameter. Instead, you're telling me it comes with a length of 25 mm and an outer diameter of 17.6 mm. Should I shorten the spring by 5 mm?
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Yes - by grinding the ends flat as described, but also by preloading it.

The Lee Spring is longer than the stock spring as well - but this doesn't matter too much. Granted, it makes it slightly harder to fit the thumb screw, but, affords more space between the coils.

IMG_20220630_114757_1.webp


The spring's 'hole diameter' is the size of hole the spring fits into with a clearance fit.
 
Opua said:
Let me clarify, I ordered the spring on AliExpress with these specifications: 2 mm wire, 20 mm length, 18 mm outer diameter. Instead, you're telling me it comes with a length of 25 mm and an outer diameter of 17.6 mm. Should I shorten the spring by 5 mm?
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No it ends up being closer to 20mm once it is fully compressed and released and the ends are ground down. The first time you fully compress it and release it it will not fully expand to it's original 25mm lenght. And it also has the same number of turns (4 turns) as the lee spring. If you selected a shorter spring it would end up being weaker.
 
Hello all,

I found this: https://www.leespring.de/en/about-us
Lee Spring via Germany. (Lee Spring GmbH, Altenaer Straße 23, 58507 Lüdenscheid Germany | Phone: 0049 2351 985 949 0)

Does someone have the partnumber of the Lee Spring for a Spark? The number LC 0857 0 M cannot be found at the German site.
 
Horatio, found it, Thanks very much. Am busy ordering it but that is bit complicated due to computer-probs on LS-side. Phoned them already.
 
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