Freestyle suspension issues

[CPGCharlie]

Hi All,

for the second time, the bolts in the offside front Watt link into the rose joints have snapped, 

has anyone had the same issue? we tried bushing the entire system to stop play as no spacers were apparent when i took ownership of the car. This was meant to be temporary but have not come across a permanent solution to the paly across the freestyle setup.

any advice greatly appreciated 

also im looking at £80+VAT for labour... where does that sit on the scale? 

[SM25T]

Where are you based ?

[7 wonders of the world]

Are you meaning the rockers on the front as there's no watts linkage at this end of the car.

I'm freestyle to you need to ensure the shank goes all the way through the rocker, you need to get longer than required bolts and trim the threaded portion down to achive the correct shank to thread lengths.

BM if you need any help.

[rgrigsby]

#1 I had a similar problem, as #3 has mentioned the original bolts supplied don't have a long enough shank. I've not had any problems since we replaced them with bolts with a longer shank, trimmed down to the right length.

[CPGCharlie]

Armenia! but only for a few more days and will be moving back to the UK and in Aldermaston. 

[Beagler]

Maybe an obvious question but are you using the the correct grade high tensile steel bolt.

[CPGCharlie]

we thought that was the issue but upgrade to the highest purchasable and still snapped -  after wrecking the bearings in the rose joints before anyone asks no I'm not aiming for potholes! 

[Beagler]

You could try titanium bolts, Dear and shouldnt really need them if designed bolts are correct grade and torque.

[ECR]

I doubt that titanium is any better in shear than high tensile steel. It sure is lighter though

[aerobod - near CYYC]

12.9 metric Allen bolts are about the highest strength readily available (or ASTM A574 grade if imperial). Normally won't cut easily without blunting a hacksaw blade, but cut-off wheels work well for trimming. Typically hex-headed bolts are not available in these grades, only at best metric 10.9 or imperial Grade 8.

[Beagler]

copied this. The original designed bolts torqued correctly though should be ok.
 

Elongation at break is the measure of a test specimen’s initial length divided by its length right before fracturing in a tensile test, multiplied by 100 to give a percentage. A large elongation at break suggests the material “stretches” more; in other words, it is more prone to increased ductile behavior before fracturing. Titanium is such a material, where it stretches almost half its length before fracturing. This is yet another reason why titanium is so difficult to machine, as it pulls and deforms instead of chips off. Steel comes in many varieties but generally has a low elongation at break, making it harder and more prone to brittle fracture under tension.

[Beagler]

Elongation at break is the measure of a test specimen’s initial length divided by its length right before fracturing in a tensile test, multiplied by 100 to give a percentage. A large elongation at break suggests the material “stretches” more; in other words, it is more prone to increased ductile behavior before fracturing. Titanium is such a material, where it stretches almost half its length before fracturing. This is yet another reason why titanium is so difficult to machine, as it pulls and deforms instead of chips off. Steel comes in many varieties but generally has a low elongation at break, making it harder and more prone to brittle fracture under tension.

[aerobod - near CYYC]

Shear strength of a 12.9 steel bolt is nominally 720MPa, compared with 550MPa for a titanium bolt. Also a 12.9 bolt has a fatigue strength at 10E7 cycles of around 350MPa compared with 240MPa for a titanium bolt. The yield point of a 12.9 bolt is 1100MPa, above the 950MPa UTS of a titanium bolt.

Except for corrosion resistance and weight, a 12.9 steel bolt will outperform a titanium bolt at any given load.

[ScottR400D]

I think the answer to this problem was in post #3

 

 

[Beagler]

Ultimate Tensile Strength

Ultimate tensile strength of low-carbon steel is between 400 – 550 MPa.

Ultimate tensile strength of ultra-high-carbon steel is 1100 MPa.

Ultimate tensile strength of Ti-6Al-4V – Grade 5 titanium alloy is about 1170 MPa.

 

The correct steel bolt designed for this application correctly torqued should be sufficient.

[aerobod - near CYYC]

Yes the correct length of 12.9 bolt would be the most appropriate here, key that the trimmed length to give a clean shank through the rose joint is used.

UTS of 12.9 bolts is 1200MPa (as indicated by the "12" in 12.9; these are alloy steel bolts, as opposed to plain carbon steel), but fatigue strength is definitely a factor, Titanium is generally not as good as steel in that respect as a % of UTS for a given number of cycles, although much better than aluminium.

[Beagler]

CPG Charlie,

What spec does the original design/ part number of the bolt call for. 

[7 wonders of the world]

Your clearly not familair with the application Beagler....... 

 

[Beagler]

Is this not it.

https://caterhamparts.co.uk/watts-linkage/4897-watts-linkage-kit-metric-chassis-de-dion.html

[7 wonders of the world]

No

[Beagler]

Is it a Caterham produced system and for road or track use.

 

[SM25T]

No

[Beagler]

Like 20 questions this.  Is this for track only or road use.

[OldAndrewE]

No, it is a Freestyle Caterham (as the topic title).   2016_02_04_Freestyle.pdf (lotus7.club)

[ScottR400D]

The mind boggles. No idea what he's offering advice on but still.........