Springs??

OK springs. If I want to buy a spring, one that isn't in my Acme box of assorted springs, what do I ask for?

OK I guess I can say x long and y in diameter and say whether it pulls or pushes, but what about strength?? I need one that will hold something up, but won't be too strong to be moved by a fairly light push.

How do I describe that. Is there a unit of springiness??

Measured in (e.g.) Newtons force per mm extension, of lbf per inch, or kgf per metre. For extension read compression also. If you are buying the kind of extension spring that comes with all the turns touching, there is also a minimum force to start to stretch the spring. For example see

**LINK**

BTW, there's a free, cut down version of the spring design software created by the Institute of Spring Technology (IST) in Sheffield. Useful if you want to check spring designs before trying to make them.

The "unit of springiness" is known as the Spring rate. This is expressed as the force required to compress, or extend, the spring by a set unit of length, such a Pound per Inch, in old money., as as above.

Spring design is quite an art, and can be very frustrating. You design a spring to give the desired rate, and to fit into the space available, but then when you check the stress, it is excessive. So back to the drawing board! When you get the stress within limits, the wire size is likely to be such that the spring is coil bound before reaching the required travel!

You recalculate and everything is now fine, except for the spring rate! And so it goes on, until eventually, if you are lucky, all falls within limits. If not, think about changing the coil diameter or the space into which the spring needs to fit?

Howard

I think Wolfie wanted to buy a spring rather than design one! I needed some tension springs to apply some lift to the roller of an etching press that I was improving, was a fairly simple matter of weighing the roller, looking at the available space and range of movement, calculating the initial force needed to just hold the roller, and finding springs from RS to suit. I ended up with 2 springs at each end and it works well.

Yes I was going to buy not make, I need a couple of motorcycle stand return springs. I don't have one of the originals

Motorcycle stand springs tend to be difficult. Need to be strong so that only minimal extension creates enough force to stop the stand bouncing up and down when retracted but have to cope with considerable extension when the stand is in operation without being overstressed. Frequently need relatively long straight lead in to clear mount bolts and the like. Centre stands are particularly hard. Generally not the sort of thing you find off the shelf.

Must be pretty obscure machine if you can't track down a stock part or near enough the same from a similar model.

My Norton Commander (the rare rotary engined beast) along with its Interpol II relations is the only motorcycle I know of that uses stock springs for the centre stand. It has a cleverly shaped intermediate swinging link at the chassis end to reduce stresses under full extension whilst still generating enough force to hold the stand up. Springs are barrel type extension ones which also helps reduce peak stress when compared to the usual straight coil.

Clive.

Should you need a spring of any type then these people are very good **LINK**

They used to have a catalogue that was an excellent cure for insomnia.

I have no connection with them other than satisfied customer.

Regards.

David.

Wolfie - is item 130742885849 on E-Bay anything like you're looking for?

Entex has a very impressive catalogue. However, like other major suppliers they are not interested in supplying small quantities. I recently needed a single special spring, and after working out all the details, rate, initial tension, extension etc found just what I needed in the Entex catalogue. Price was a mere £1.80. Problem was I would have had to buy 25 and pay a hefty postage charge. Effectively £50+ for 1 spring!

Try Lee springs (no connection) They have an excellent site with downloads that list springs in size order with a separate column showing loads/ length etc. really easy to pick what is wanted. each spring is classed with a group letter as well as a reference number. All springs in the same group cost the same so easy to work out costs as well.

Max

I can recommend 'Ashfield Springs' near Mansfield, Nottinghamshire. They have an on-line cataloque, are very helpful on the 'phone and will often let you have the odd spring as a "free sample", especially if you can collect.

Here's another company to try - MORRIS SPRINGS. They have a very useful catalogue you can bring up on line, listing springs in well-laid-out incremental tables displaying all the vital information for each spring. I've used them on several occasions for single springs or very small quantities. Not cheap, but the springs accurately mirror the tables' information, which is wanted I needed. Hope you find them equally useful.

Wolfe,

private message me for an address of a guy who'll make u what u want.....he makes" all mine in st/st as I'm a nutter..hahaha......he's not expencive, will happily make one and to ur pattern..........

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