Driveshaft loops mounted to tunnel - updated

[deecee]

hi all,

Currently looking at fabricating the driveshaft loops for my friends R30 Skyline and am wondering whether I can mount the driveshaft loops to the transmission tunnel with the doubler plates on the other side.

Most examples of driveshaft loops I have seen, use flat bar in a horizontal position to mount to the underside of the floor pan, but I would like to package the driveshaft loop more efficiently within the space of the transmission tunnel.

Any guidance would be appreciated.

Thanks
Dave

[Leon]

Hi Dave,

Yes you can mount to the transmission tunnel with doubler plates.

From the Hobby Car Technical Manual
5.22.3
A drive-shaft safety loop fitted to a low volume vehicle must be
attached either:
(a) directly to, or incorporated within, a chassis or sub-frame
rail, or a rigid cross-member; or
(b) where it is not practicable to attach a drive-shaft safetyloop
to a chassis or sub-frame rail, or rigid cross-member,
to the vehicle floor using doubler plates which have a
minimum mating area of 3000 square mm, and are as
close to square as can be practically achieved.

Supplementary information to that:
5.22.3
A typical size plate
meeting the requirement
of 3000 square mm
would be a 50 mm x 60
mm plate, or larger.

[deecee]

Thanks for confirming

[deecee]

Good morning,

Blue lines indicate position relative to the centre of the joint.

Is the loop acceptable in this position as the flat bar and reinforcement plate would be against flat metal vs contoured (can't distinguish from pic sorry) and we have to avoid interference with the handbrake cable. Just want to ensure that the position is correct to ensure that in the event of a failure, that the loop would function as required.

Cheers Dave

[Leon]

Hi Dave,

I apologise if I've misread the intent of your question, but the driveshaft safety loop must be fitted within 250mm rearward of the front universal (as per the infosheet).

www.lvvta.org.nz/documents/infosheets/LVVTA_Info_09-2011_Drive-shaft_Safety_Loop_Requirement_Clarification.pdf

Agreed amended requirement:
Section 5.22.2 item (a) – it has been agreed that the existing requirement for the drive‐shaft safety
loop(s) to be mounted within 150mm (6’’) rearward of the front drive‐shaft universal is too restrictive,
because some vehicles do not have a suitable mounting point within this 150mm range.    The TAC has
agreed that this will be changed within the Hobby Car Technical Manual at the next amendment
opportunity to 250mm (9.8’’).   In the interim, LVV Certifiers may apply this new agreed requirement,
effective immediately.
There is one proviso however, and that is in cases where a drive‐shaft is very short, in which case the loop
must be positioned far enough forward to be effective, and to prevent the shaft from contacting the
vehicle floor, or the road surface.  In the case of very short drive‐shafts, 250 mm may not prove effective,
so this must be considered in each case.
Paragraph 5.22.2 of the HCTM will be changed in due course, but the agreed change may be applied
immediately.  

[deecee]

Where I want to position the loop is within 100mm of the universal. I am trying to clarify if the position of the loop as indicated by the blue lines, is acceptable as it relates to failure scenarios.
Left hand side of pic is rear of car, right hand side is front/engine of car.

Within the specified range of up to 250mm from the universal, failure may from the universal letting go or the shaft twisting and breaking.
Maybe I am over-analysing this, but if the shaft fails 30mm behind the universal to shaft weld, then the loop is not going to perform it's function.

Or is it accepted that if the loop is withing the defined range from the universal, it can be certified on the assumption that most common cause of DS failure is the universal?

[Leon]

Hi David,

I think I now see more clearly what you are asking.

The scenario the driveshaft safety loop is written for is the one where the front of the shaft drops to the ground and you polevault, or causes a lot of damage as the broken end spins. So yes, the expected failure point is the joint, or the where the tube is welded to the joint.

That is not to say that this is the only possible failure point. So, if you are concerned, you are perfectly welcome to have further loops, if you want to contain the potential energy involved in a driveshaft failure. Our requirements on safety loops are the minimum, rather than a maximum.

[deecee]

Thanks for the explanation and perspective of minimum requirements. I was wondering how to interpret the guidance and now I have a better feel for how to move forward.

Cheers
Dave

[vgturbo]

Sorry to dig up an old thread ive got mine mounted to the tunnel in my ute but im having thoughts on weather theyll pass, they're held on with 4 16mm bolts solid as houses but is only being mounted to the top of the tunnel to spec?

Heres a pic of the loops ( red dots are the holes)

[Leon]

If I'm reading you right, and they're just bolted into panel steel, then you'd need a doubler plate on the inside.

Our driveshaft safety loop infosheet has had a bit rewrite, so have a read through

www.lvvta.org.nz/documents/infosheets/LVVTA_Info_07-2016_Drive-shaft_Safety-loop_Requirements.pdf

[vgturbo]

O sorry yea i have bolted it to double plated 6mm plate on otherside of tunnel but just was curious if that would pass as its only mounted to top of the tunnel, not to 2 separate points like alot of loops that are around