Helical Compression Spring Design

[Ussuri]

Evening Folks,

I'm intentionally trying to get myself into deep water. I am looking at designing/specifying a helical compression spring, but being honest, I know next to nothing on the subject. I think we covered it at university many moons ago.

So, I would like some pointers, effectively an idiots guide you might say.

I know I should get one of my mechanical colleagues to do it, but we haven't got many at the moment and those we have are far too busy on more important stuff. So instead of leaving it on my desk for 6 months I thought I'd have a crack.

Any help would be much appreciated.

 

[CoryPad]

Here is the place for spring design publications:

http://www.smihq.org/public/pstorep.html#book1

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[israelkk]

Spring design may seams to be quite a simple job, but the truth is that it is quite a complicated and specialized issue which requires a lot of experience and knowledge. A bad designed spring can do a lot of harm. If time is an issue why not outsource the job to an external expert engineer?

http://israelkk.googlepages.com/home

 

[rorschach]

I've used this online calulator and it has agreed quite well with data generated by engineered spring products here in Houston.

http://icrank.com/cgi-bin/pageman/pageout.cgi?path=/data/spring/spring.htm&t=2

 

[MikeHalloran]

After you learn how to design good springs, you'll also learn that the ones in the catalogs are pretty decent. If stock springs exist in the load range you need, and you think you need something entirely different, you need to think some more.



Mike Halloran
Pembroke Pines, FL, USA

 

[Ussuri]

Thanks Folks, and to be honest I will probably select something from a catalogue. I just dont like picking stuff when I have no idea about the engineering behind it.

Israelkk, just to put your mind at rest, this spring I am looking at is a one time use and will only be used to push two steel plates together, no load cycles. Its of such minor importance the clever guys probably wouldn't even bother looking at it.

 

[mog69]

Ussuri
Never underestimate the importance of any element in a system - consider the impact on the process / procedure / operation if the spring doesn't achieve it's purpose. Examine the design - if the spring is essential, then it's purpose is essential. "Never spoil the ship for a ha'pth of tar"!

 

[israelkk]

It may be used one time but how long it will be loaded? In aerospace products many times static loaded spring can stay loaded for 20 years. If this is your case then you should expect relaxation. A spring that will be loaded for long periods may loose large portion of the expected load.

http://israelkk.googlepages.com/home

 

[Ussuri]

A bit more background. Its for a structural steel connection on on a temporary works steel frame. I would expect from fabrication to disposal about 6 weeks.

I am attempting to detail a 'quick release connection' This steel frame will be deployed subsea and needs to be dismantled by an ROV. The spring idea was to go on a bolt with a large cotter pin to ensure the end plates stay in contact. Basically a large spring nut. The cotter pin can then be pulled out by the ROV and the connection dismantled. The connection should not be loaded at all and I am designing for the case of accidental impact.

Any alternative suggestions perhaps?

 

[Philrock]

All the formulas for stress, deflection, spring rate, etc. are in Machinery's handbook. It'really quite easy to write an Excel spreadsheet to design or analyze springs in a cursory manner. I put the entire Century Spring catalog into my spreadsheet. (Actually 2 spreadsheets - one for compression; one for extension). I have yet to encounter an occasion where one of their springs would not do the job.

Israelkk is right, however, about the complexity of doing a thorough job. Fatigue, relaxtion, temperature, and material properties are all part of the picture.

 

[Ussuri]

Machinery's handbook, sounds useful. Where might I get a copy?

 

[Philrock]

Anyplace that sells technical books, including Amazon. To shop for price, try

http://www.bizrate.com.

 

[CoryPad]

It is published by Industrial Press. Here is their Internet site - it has some extra information, interative demo, etc.

http://www.industrialpress.com/en/MachinerysHandbook/default.aspx

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MikeHalloran]

Ussuri, when you buy a machinist's tool chest, it will have one deep narrow drawer with a hole in the bottom. The hole is so you can use your finger to get your Machinery's Handbook out. Yes, the drawers are standardized just for that one book, and the book stays the same size so it will fit the drawers.

It's useful to engineers, too.




Mike Halloran
Pembroke Pines, FL, USA

 

[Cockroach]

You know, the absolute bible on the subject is Mechanical Springs, Wahl, Edition 2, Spring Manufacturer's Institute. I managed to get this book online at the website in November 2003, receiving a tip at this forum.

Absolutely the best reference I could dream of, better than Timoshenko, which is a statement in itself.

Good luck, but really, just passing on the fortune.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada