Roadholder external springs

X-file said:

When the tightly wound end of the spring becomes compressed, it becomes a solid mass.
If that's on the slider end of the spring, you have increased unsprung mass.
It always better to have less unsprung mass, and more sprung mass is not a problem.

Tightly wound coils to the top will perform better.

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Not sure what you mean by "solid mass". The mass of the spring doesn't change when it's compressed.
Besides, the external springs are mounted on top of the fork sliders. Isn't the "unsprung weight" the weight of the wheel and roughly the lower half of the forks? The external springs aren't in this vicinity.

mschmitz57 said:

OK, this is just weird...

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I don't think it's weird at all. Most things are done for appearance thesedays, and very little is done for performance.
If those springs were fitted right way up, you wouldn't be able to see the close-wound coils and know they were special. They would, of course, perform better right way up, but there's no "show" value.

As soon as the close-wound coils become coil-bound (which they must, to achieve progressive spring rate), they are a solid mass on top of the slider. That mass is added to the mass of sliders, wheel, and part of the dampers to make up the total unsprung mass. Unsprung mass is something that should be kept to a minimum.
That is better achieved with the close wound coils to the top.

X-file said:

mschmitz57 said:

OK, this is just weird...

Click to expand...

I don't think it's weird at all. Most things are done for appearance thesedays, and very little is done for performance.
If those springs were fitted right way up, you wouldn't be able to see the close-wound coils and know they were special. They would, of course, perform better right way up, but there's no "show" value.

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What?? How can you say that?
Modern motorcycles perform better in every measurable way.
Modern sport bikes will outperform factory race bikes from a few years ago.
C'mon!

mschmitz57 said:

What?? How can you say that?
Modern motorcycles perform better in every way.

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I'm too old to be fooled by that claim. I'm also too good at physics and mechanical aptitude. Tell it to someone younger.

OK, Fair enough (just trying to keep the conversation lively).

Aw Nuts!
It looks like I had them installed correctly at one time.
Although they do look better upside-down.

I would like to fit some external springs to my Commando, mostly just for looks, do they make that much of a difference to the suspension, or is it possible to compensate with the internal springs?

The closely coiled part of the spring is the softer, so that's what's 'gives' first.

Therefore, with a progressive spring, the closely coiled parts (the softer parts) will absorb mild road bumps before the stiffer part moves at all.

Therefore, over mild road bumps the stiffer part of the spring does not compress.

Therefore, if you install the springs with the closely coiled part at the top, then over mild bumps, the stiffer part of the spring will be sitting 'unmoved' and is subsequently adding to the unsprung weight...

Therefore, the correct mounting of progressive springs is to mount the softer part of the spring closest to the point of movement, in other words, to the bottom.

This is pretty much indisputable from the theoretical perspective. However, in reality, I doubt anyone could detect the difference!

Eddie, think about that, the slider doe's not move its static . ie fixed to the ground via the wheel. only the frame move's....so the closest point to movement is at the top. does that compute?

Fast Eddie said:

The closely coiled part of the spring is the softer, so that's what's 'gives' first.

Therefore, with a progressive spring, the closely coiled parts (the softer parts) will absorb mild road bumps before the stiffer part moves at all.

Therefore, over mild road bumps the stiffer part of the spring does not compress.

Therefore, if you install the springs with the closely coiled part at the top, then over mild bumps, the stiffer part of the spring will be sitting 'unmoved' and is subsequently adding to the unsprung weight...

Therefore, the correct mounting of progressive springs is to mount the softer part of the spring closest to the point of movement, in other words, to the bottom.

This is pretty much indisputable from the theoretical perspective. However, in reality, I doubt anyone could detect the difference!

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Fast Eddie said:

The closely coiled part of the spring is the softer, so that's what's 'gives' first.

Therefore, with a progressive spring, the closely coiled parts (the softer parts) will absorb mild road bumps before the stiffer part moves at all.

Therefore, over mild road bumps the stiffer part of the spring does not compress.

Click to expand...

That is totally wrong !
All windings are subjected to the same load , and compress together .
The spring rate only increases when the closer wound coils become coil bound .
Something that will never happen with most so called 'progressive' springs .
There is not one picture of a progressive spring shown in this thread .

This is what truly progressive springs looks like :

slighter better to place the tighter densor coil mass on the fixed end at top as the 'straigther' stiffer end will shove the tighter coils even denser before stiffer oriented coils compresses. Watch a dropped slinky to see some the prinicples showing large sections of spring can compress before the distals parts move. i love the external spring look and filling in the skinny weak looking bare stanicons like recoil spring on heavy air craft guns. All springs as long as in forks with aslo lean pressure agasint the stansion so internal lubed springs my be less restriction. Motion of 2 objects is relative but can name one end fixed by which end extra mass matters most on.

I am with you Ludwig all the way you are 100 percent correct , some times it is a bit like being Marco Polo here on the forum the earth she's a round then the masses reply no no Marco she's a flat . Ha!!!!!!! Work it out yourselves is it easier to compress the more open coils on a spring or the more closely wound given the same wire diameter? Another myth busted . Sorry do not mean to offend but some times new members to the forum can get the wrong info or myths . Keep it correct .

i also agree with ludwig on this

mounting the spring either way up it still has the same weight / force acting upon the coils the spring rate only increases as the coils become closer

unsprung weight does the spring weigh less if turned over ?

Well i dont agree!
Ludwigs picture shows a "duel rate wound spring" when or if, the poundage of the close coils exceeds the Lbs/inch of the wide coils ,then those wide coils will start to compress before the close ones become total coil bound. Eg . Close coils are 15Lb/inch ,wide 30Lbs .as soon as the close coils have compressed 2 inch..this is now equal to the wide poundage...from this point the wide coils are starting to close. at 1/2 the rate.

Ludwigs comment on the close wound springs becoming coil bound before the main body of the spring starts to compress

may not be the perfect way to describe how the springs work as the loose wound springs will / should start to compress before the close wound ones become coil bound
there will be a tipping point where both tight and loose wound springs are operational

but the point i make they will be subject to the same force which ever way up they are fitted

For the same wire thickness , a closer wound spring will be softer , because more wire per inch of spring length .
If you load a dual wound spring , ( like in John's example 15lb/in and 30lb/in ) , the spring will act like a 15lb/in spring , TILL the closer wound coils get coil bound .
From then on , it will act like a 30lb/in spring .
The cross over point depends on the ratio between closer and wider windings .
But : BOTH sections will ALLWAYS compress at the same time ( but at a different rate ), because they are both subjected to the same load .

I would think that is pretty obvious ?

The springs shown on the Hagon shock are dual rate , but the closer wound section will NEVER become coilbound before the end of travel of the dampers , so in practice they are linear springs .

About wich side up : the closer wound end of the spring is heavier , so there is an advantage to have that side up , for lower unsprung weight .

mounting the springs with the coils at the bottom to decrease unsprung weight

this is what i consider a grey area is it unsprung weight or sprung weight the springs are supported above the moving suspension parts

Taking your mobile phone out your pocket before you ride will have a more positive effect on handling than turning the springs over

Sorry Ludwig, but you stated the spring rate will only increase when the close coils are coil bound? mayby i have lost something in the translation?
You are correct in stating the springs shown are true progressive . When load is applied the soft coils will start to compress the wide coils in a ratio of how much each coil is rated/ wound.. just done this in the workshop! I placed a 12lb spring on top of a 40lb spring , the 40 lb started to compress straight away ..but very slow ....Then with more compression of the two the 40 lb reacted to the 12lb after 25 mm the stronger was now just over 3.3 mm shorter.

ludwig said:

For the same wire thickness , a closer wound spring will be softer , because more wire per inch of spring length .
If you load a dual wound spring , ( like in John's example 15lb/in and 30lb/in ) , the spring will act like a 15lb/in spring , TILL the closer wound coils get coil bound .
From then on , it will act like a 30lb/in spring .
The cross over point depends on the ratio between closer and wider windings .
Both sections will ALLWAYS compress at the same time ( but at a different rate ), because they are both subjected to the same load .

I would think that is pretty obvious ?

The springs shown on the Hagon shock are dual rate , but the closer wound section will NEVER become coilbound before the end of travel of the dampers , so in practice they are linear springs .

About wich side up : the closer wound end of the spring is heavier , so there is an advantage to have that side up , for lower unsprung weight .

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Dear dudes a proper designed spring in our suspension lengths will begin to compress the weaker tighter coils first and most but all the spring coils will compress to some degree before the tight end coil binds till only the more open stiffer colls left to move. Until the whole spring coil bound the denser end will be the tighter coil end so a bit better to put that end at the fixed end where extra mass has least effect on inertia. An example is hobot 6" travel Roadholders instead of the stupid travel limiting top bush extensions for top out hydrualic stops I used a highly progreessive valve spring - which leaves forks ~2" taller stance but could just a well put in a very weak spring spacer that's always coil bound compressed when any weight on forks for normal sag height but still allows 6" travel to keep front tire in contact on full silent soft stop extension. For max performance on smoothish surfaces a linear spring is better as progressives have some slop over the range of the weaker wound section but rough riders like the progressives better. Trade off is stiffly sprung racer vs more comfortable street use. Progressive springs can be wound so they function as two springs with a easy to move range and a stiff to move range OR with more gradual col angle so a smoothly progressive rate.

Me thinks this one will run for a while yet!

To Frankie, what is sprung / unsprung isn't really all that much of a grey area. Parts that move with the road undulations are unsprung. Parts that are isolated from this are sprung. So... The front wheel, wheel spindle, fork legs, damper tube that is fixed to the fork legs, are all 'unsprung'. Whereas, the stanchions, yokes, damper rod that is connected to the fork top nuts are all 'sprung'.

The springs are in the middle of this, so I guess they are a grey area.

If, as Ludwig also says, the softer part of the spring allows more spring movement than the stiffer part, then the softer part will effectively be the part absorbing the most undulations. Therefore, if this part is at the top, with the stiffer part sitting on the fork leg (moving with the road undulations) then that stiffer part will be effectively adding to the unsprung weight. If it is sitting on top, isolated from the undulations by the soft part of the spring, it will be sprung weight.

At least that's how it appears to me! But, it really, really is quite academic and I doubt that anyone could actually tell the difference when riding.