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Kestrel Centre Stand Return Spring

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Kestrel Centre Stand Return Spring

Post  Science is Au on Sun Jul 22, 2012 11:28 pm

Mine is missing making it a bit bothersome to do anytihng with the bike.

Can anyone provide me with dimensions please.

I used to be a springmaker and thought I had a box of various bits sitting where I wouldn't teip over it, but must have chucked it some time ago.

Wire gauge, number of coils, OD of spring, hook lengths and ID of hooks.

Thanks
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Science is Au

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Return Spring

Post  MoscowFlyer on Mon Jul 23, 2012 5:33 am

Hi, here is a pic of a Kestrel centre stand and return spring, I have no idea of the dimensions, hope this helps. Mike
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Re: Kestrel Centre Stand Return Spring

Post  Science is Au on Mon Jul 23, 2012 6:21 am

Mike

Thanks for that, I have the same picture, it shows 17.5 coils.

I think I need someone to actually measure their spring to get it workable.

Thannks

Grant
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Science is Au

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Kestrel return spring

Post  bessybarnett on Mon Jul 23, 2012 3:31 pm

Grant,

I have put together an Acrobat PDF file of the measurements of my spring on a photo together with few other photos of my Kestrel stand and spring in position. Hope it helps.

The best way is to send me a private PM with your email address and I will forward the PDf to you. If you are not sure, the 'PM' facility is just below my avatar picture on the right. Click on that icon and send me your message.

Pete
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Kestrel 66 Stand return spring

Post  bessybarnett on Mon Jul 23, 2012 4:43 pm

Grant, forget the Acrobat PDF file, I have managed now to export the file as a jpg, and then into Photobucket.

There is a wire 'spring restrictor' (if thats what they call it!) on the coils to keep it to 80mm in length. The smaller hook connects to the stand. The spring works very well. Hope the photo helps.

Pete

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Re: Kestrel Centre Stand Return Spring

Post  Science is Au on Mon Jul 23, 2012 9:37 pm

Pete

Excellent information, thanks.

I must be missing some part where the spring fits the frame as the locating hole on my stand is 188mm from the nearest "logical" place where the top of the spring can fit i.e. the footpeg support bar, but nothing shows up in the spare parts list.

I might need to custom make one until I sort it out.

Cheers, Grant
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Return Spring

Post  bessybarnett on Mon Jul 23, 2012 10:47 pm


Grant, top end of my spring fits over the support bar for footrest and brake pedal as in photo.

Pete

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Re: Kestrel Centre Stand Return Spring

Post  Science is Au on Mon Jul 23, 2012 11:46 pm

From the dimensions of your spring and the distance it has to open to, I calculated it would be overstressed from the beginning, hence the open coils in the body of your spring.

I remeasured the stand on the bike and have the dimensions of 135mm when up and 175mm when the stand is down.

From memory, 2.34mm is an odd size of wire to source, 2.0mm, 2.24mm and 2.5mm are the standards for spring wire these days.

The stand is not heavy, so not much initial load is required to hold it up when closed, so we can drop to a lower wire size eg. 2.24mm.

Even with the lower sized wire, the stress at maximum opening is still going to cause the spring to fail, to reduce this we can either increse the length of the hooks, increase the body diameter of the spring, increase the amount of coils in the spring, decrease the wire diameter to name a few.

The best bang for the buck seems to be increasing the body diameter of the spring by 4mm to 21mm OD and adding a couple of extra coils. We don't want to increse diameter too much as it may foul on the stand (shouldn't because of the extended hooks) or the stand bolts.

I might get a couple made up and if all goes well, I can send one across to you for your help Pete.

Thanks

Grant
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Return Spring

Post  bessybarnett on Tue Jul 24, 2012 6:59 am

Grant, I assume you have tried to source another bike return spring on the interweb. JH may recognise my spring in the photo as possibly coming from another source i.e. BSA, Enfield? I don't know but this could save you alot of time making one, now that you have the dimensions of a spring that works.

Just a thought.

Pete
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Re: Kestrel Centre Stand Return Spring

Post  Science is Au on Tue Jul 24, 2012 7:07 am

Pete

As stated earlier, I used to be a springmaker and still have some contacts, I'd have one by tomorrow if I was not heading interstate on business, I'll pick it up on Friday when I'm back.

Cheers

Grant
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Re: Kestrel Centre Stand Return Spring

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