progressively wound coil springs
Posted by rkj
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I'm doing this here because this is about one of my motorcycles, and I need your brains for a sec. Yesterday I was putting together my forks (I'm rebuilding the front end, new brakes and tire) and just as a last bit of clean-up before I put them together I took the springs out of the fork tubes and measured (and cleaned the inside of the tubes)) the springs, they measured fine but they were in upside down. The book says the tightly wound end was supposed to face up so it was at the top of the forks, by the bars. I was just wondering if any of you guys might hazard a guess why that is and I wonder if our "is-es" cars are the same way. Both models are supposed to have progressively wound springs; that's why our cars, stock, have great compliant front ends over the usual stuff and hang in there when you push them in to a turn hard. Janet's car does not have this and there is a big difference; its like a mush pit if you throw it into a turn hard, dangerous I would say even with upgraded shocks.
I think by having the tight coils upstairs and the open coils by the wheel it works the same way on my 650, any takers? Please. Regards, Rick 
perseverance furthers |
I'm not sure it would make any difference as far as to how the spring performs. It's mos likely more to do with how the ends of the springs fir into their respective seats. As always, I'm open to being educated 
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Peter, The mounting is identical on both ends, honest!  hows the weather?
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Oh I believe you; they must have had some reason for the installation orientation though. We ended up with about a foot over night. Got the driveway all cleared and the sunshine melted the little I couldn't scrape off...which has now frozen to a perfect sheet of black ice 
We get a bit of a reprieve tomorrow before another foot is expected on Wednesday and more into Christmas day so it will be a white one 
Just got a call from my younger daughter...from the hospital. She took a dump on her snow board a couple of hours ago and buggered her back
She got a nice ride down to the lower parking lot in a helicopter then an ambulance ride to the emergency ward. She wanted them to put the siren on but they said she would live 
She's waiting to go in for X-rays and an ultrasound to see what she messed up. Hopefully she's just done some major bruising. She's going to be sore for Christmas; that's for sure. |
Ohhh, poor baby. I hope she's not banged up too bad Peter. You'll just have to love her a little extra now that she is hurt! (I'm an expurt in these areas). I'm glad you'll be having a white holiday, we have 50 degree temps coming at us with rain. Oh well, maybe next year I'll go north for christmas! Peace Bro |
She called about 1am...they were waiting for a taxi to take them home from the hospital. The X-rays and ultrasound found no broken bones and no spinal damage, just some minor muscle damage that will heal up nicely but she's going to be in a world of hurt for a couple of days
We'll go over and visit her today. This will have to be our Christmas day visit since she won't be up to traveling on the bus and we probably won't be able to get out of our street with the extra foot of snow forecast for tomorrow and Christmas day. I'm sure her partner will be treating her like a queen Edited 1 time(s). Last edit at 12/23/2008 07:32AM by Archeo-peteriX. |
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She called about 1am...they were waiting for a taxi to take them home from the hospital.
The X-rays and ultrasound found no broken bones and no spinal damage, just some minor muscle damage that will heal up nicely but she's going to be in a world of hurt for a couple of days[/quote] Been there, R+R with a few IB's should hopefully do the trick. I always find recovery is a great time to think B) Give her a kiss from the both of us Pete 
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Been there, R+R with a few IB's should hopefully do the trick. I always find recovery is a great time to think B) Give her a kiss from the both of us Pete [/quote]
Will do and thanks for caring Rick
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That seems like a logical deduction ... good thinking
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I think the reason they're mounted with the more open coils close to the wheel is to keep the moving mass to a minimum.
John[/quote] Thanks John, I wish I could understand this more; "moving mass to a minimum", I just thought it would be more sensitive that way. I guess things like this are hard to explain or put into words. I've always liked the way, both the es and the is drove; they are very supple over the small stuff (not ridged like hard springs and you could push them into turns hard without washing them out. I've had serious car collectors in my car and they all have commented on the suspension. It should be interesting to finally get the bike together and see what the difference is I looking forward to that!
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I think you actually do understand it. Making the suspension more sensitive is exactly what you do by mounting the spring that way. I'll try to explain why without turning this into a senior level ME course in vibrations.
Think of it like this: The wheel is moving up and down and the springs and shocks are what try to keep that movement under control. The heavier the wheel, the harder it is to keep it under control, which means that as the wheel gets heavier, you need a stiffer spring and heavier shock to control it. Make sense? This is just like the idea that it's harder to stop a heavy car, so you need bigger brakes - inertia. Now think about that variable rate spring. If you tie a rope around the coil right in the middle and hold it up, it won't hang level. The end with the tighter coils will hang down because it has more coils and is therefore heavier. Now look at how the spring mounts with the wheel. One end of the spring is against the frame of the bike, or fork, and the other end is close to the wheel. The end near the wheel moves with the wheel, so even though the spring is part of what keeps the movement of the wheel under control, it's also contributing weight (mass) to the stuff that needs to be controlled. Since a variable rate spring has a heavy end, it makes sense to mount the spring so the lighter end is at the wheel. that way you have less weight (mass) to control. Since less weight is moving, it will be more sensitive and easier to control. At least that's how I reasoned it out before I sent my one line post.
John |
Your logic is sound and it does make perfect sense. I'm glad you thought it through and were able to give a very satisfactory explanation
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Thanks John, sounds good to me 
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