Seamless tube

[BlaydonBodger]

Ok I am about to make some bones and and I would love to know why was it decided that 19mm seamless was the way to go for top wishbones? Why not 18mm or 20mm? :confused:

From what I am led to believe, in industry, 18mm and 20mm are by far the more frequently used tubes and hence far more easily obtained by the likes of me who is building in true locost style and trying to spend nothing whatsoever:)

I am just a little curious to know where the 19mm came from particularaly as i have about 5m of 18mm hydraulic seamless with a 2.65 wall (I think) which was very kindly donated:D to the cause lying in my workshop.

So what do you guys think; should I throw caution to the wind and use the 18mm tube?

[Jimmyd]

Ok I am about to make some bones and and I would love to know why was it decided that 19mm seamless was the way to go for top wishbones? Why not 18mm or 20mm? :confused:

From what I am led to believe, in industry, 18mm and 20mm are by far the more frequently used tubes and hence far more easily obtained by the likes of me who is building in true locost style and trying to spend nothing whatsoever:)

I am just a little curious to know where the 19mm came from particularaly as i have about 5m of 18mm hydraulic seamless with a 2.65 wall (I think) which was very kindly donated:D to the cause lying in my workshop.

So what do you guys think; should I throw caution to the wind and use the 18mm tube?

You are correct 20mm is more readily available and I know many have used it. Although someone with real engineering experience will probbaly come along with reasons why not to, if I had the 18mm costing nothing I'd use it. Sometimes I wonder if Chris used certain sizes simply because he had them available? I may get shot for that comment.

J

p.s. I don't know why the unhappy face is in this reply but I can't get rid of it!!!!

[Enoch]

Maybe it's because 19mm is the closest to 3/4 inch? If he had 3/4 inch to hand, used that then converted it to metric it would have come out at 19mm.

[Talonmotorsport]

You can use 18-20-22-25mm -3/4" 7/8" 1" CDS if you want for the top wishbones or even ERW if your saving money although I would'nt go lower than 2mm wall. I've done a few pairs of top fronts in 25mm tube and they look quite chunky. I would not use hyd. grade CDS though as it's anealed so it can be formed to tight bends.

[Bonzo]

Maybe it's because 19mm is the closest to 3/4 inch? If he had 3/4 inch to hand, used that then converted it to metric it would have come out at 19mm.

Yep that's my view too :)

Wishbones have traditionaly made from 1" & 3/4" tube, probably going way back to the original Lotus 7

As Enoch said, this equates to 25mm & 19mm in metric.

If memory serves me right, the original lo-cost had wishbones made from 1.6mm wall thickness tube !!??

Personaly, I would use the 18mm tube that you have to hand, the wall is certianly thick enough.

[AshG]

i used 20mm because it was what i had look at the top wishbones on a caterham they are about 15mm

[fabbyglass]

Most if not all Kit Car firms use 14swg ERW not CDS

[flyerncle]

Got plenty of ends if you want them Mick,let me know I will fish them out.

[BlaydonBodger]

Thanks guys some great info there

Talon, you say you wouldnt use hydraulic as its annealed yet hydraulic tube gets a mention in the book.... I am just trying to get some perspective here... are you suggesting it shouldnt be used or are you saying its ok but there are better options? I have had a quick look at the specs and tensile strength is comparable to othe rmechanical tubes but yield is quite a bit lower.

Thanks Flyer no doubt I will be pestering you tomorrow if thats ok. It will be good to have a bit of a catch up have made a bit of progerss on that daptor plate.:)

[flyerncle]

Nice to see you Mick I am there till 5pm so any time.

[Talonmotorsport]

Thanks guys some great info there

Talon, you say you wouldnt use hydraulic as its annealed yet hydraulic tube gets a mention in the book.... I am just trying to get some perspective here... are you suggesting it shouldnt be used or are you saying its ok but there are better options? I have had a quick look at the specs and tensile strength is comparable to othe rmechanical tubes but yield is quite a bit lower.


I would have thought that when Haynes approved the design of the wishbones some one said that CDS had to be used 'for safty sake' in case any thing fails and they become lible for it. I guess it is intended to stop people from using bits of any old tube that they have laying around which might not be up to the job.
Hyd. CDS is softer than Mech. grade which makes it easier to bend not realy what you want in a wishbone. Don't forget that hyd. CDS is ment to have high pressure oil running through it but not support any toursional load. So although the spec chart shows it as being simular to Mech grade don't forget how it is being used.
All that aside you could use ERW I only use Mech. grade CDS as that's what the book says and it stops any come backs from customers claiming that my parts are made on the cheap with incorrect materials.
At the end of the day it's your time and money and you choose where you want to spend both.

[BlaydonBodger]

Thanks talon, I have a westfield top bone in front of me now and I have to say it is rather light and doesnt seem that substantial. Not sure what its made of but may be as fabby suggested. Will do a bit more pondering before I decide what to do.