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Author: Subject: Crumple zone in protective steering?
rcx718

posted on 3/12/16 at 03:21 PM Reply With Quote
Crumple zone in protective steering?

I've read the protective steering section of the IVA manual four times now :/
If I understand it correctly it wants a crumple zone if the steering rack is ahead of the axle.
But going through old posts, people aren't doing that.

As I understand it, the "vehicle and steering column assembly must be designed" to protect the driver and the annex gives examples of how to do this. It doesn't state how many methods need to be used, e.g. if having a collapsable column is enough by itself. But it does say "check for some energy absorbing device" and gives 5 examples like absorbing bumper or crumple zone.

I've tried emailing VOSA before with questions and never got a reply!

In the IVA manual:

14 Protective Steering.
Point (4) Reads:

The vehicle and steering column assembly must be designed such that in the event of a frontal impact at 48km/h the rearward horizontal displacement and vertical displacement of the top of the steering column and its shaft do not exceed 127mm. The vehicle should be assessed using the material in Annex 1.

Annex 1
The vehicle structure ahead of the steering rack or box
Of primary concern is the position of the steering rack or box. If the rack or box is ahead of the axle centreline, there will clearly be less of the vehicle
structure available to deform and absorb energy than if the rack is behind the axle. Check for some energy absorbing device such as
1. an energy absorbing bumper, or bumper mounting (e.g. mounted on hydraulic dampers or telescopic tubes);
2. a crushable section of chassis comprising one or more deliberate weaknesses;
3. in the case of a tubular chassis, a deliberately un-triangulated bay or arrangement of tubes likely to deform progressively;
4. in the case of a composite monocoque an area of bodywork which the presenter can demonstrate has been designed to crush progressively and
dissipate energy;
5. in the case of any vehicle, a non-structural nose cone of any material which the presenter can demonstrate has been designed to absorb energy.

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rcx718

posted on 6/12/16 at 06:35 PM Reply With Quote
I've emailed VOSA to ask.

Is anyone putting crumple zones into their Locosts?

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turbodisplay

posted on 6/12/16 at 09:16 PM Reply With Quote
Mines not a locost, but I`ve takem the crash bar from a peugeot 407.
It has two sections designed to crumple and disipate energy.
In a low speed impact the cost/easy of repair will be low. Just buy a replacement from ebay.
Thanks
Darren

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907

posted on 7/12/16 at 08:25 AM Reply With Quote
Normal designs for steering columns will incorporate an 11 degree dog leg between universal joints;

or

a telescopic section, the triangular Sierra column section being the most common;

or both.

The column must be fixed solidly to the bulkhead for either of these to work.



The steering wheel should also have a collapsable section or be mounted to a collapsible boss to absorb the possible impact
of the driver being thrown forward. Unlikely as we sit low and long legged and have full harnesses, but rules is rules.





Not hard to prove the crumpleness (is that a word?) of the nose of a seven, or indeed the bendabillity (is that also a word?)
of the chassis or wishbones. (can of worms)


Paul G





Member of the Suttol Owners Club, the MX5 Owners Club and the BMMC

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rcx718

posted on 21/12/16 at 03:17 PM Reply With Quote
I've had a response from VOSA. They have said that the annex is for guidance and only the bits in the "Required Standard" are compulsory, i.e. in this case, a frontal impact at 30mph must not give more than 127mm displacement of the steering column. So the annex saying that a crumple zone is of "primary concern" does not mean it's required.

Phew!

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