MSA approved ROPS clarification/modification

[Rich Vaughan]

Help please?
I've decided to add a petty strut and a side impact protector(across the door opening) to my Westfield. The  car currently has an MSA approved 45mm ROPS - ie a single 45mm dia. roll hope with a 45mm dia. diagonal and 2 rearward facing 45mm dia. down braces.
I'm proposing making the petty strut and side impact stuctures from 38mm x 26.mm cds tubing.
I've been trying to decipher the blue book ruling for what I'm proposing and as usual it is confusing.
There seem to be two types of member:
Mandatory and Optional.
 Section K1.4.1 specifies tube sizes as being:
Minimum Dimensions (Ø in mm)
(a) Mandatory tubular members
45 x 2.5 (1.75” x 0.095”) or 50 x 2.0 (2.0” x 0.083”).
38 x 2.5 (1.5” x 0.095”) or 40 x 2.0 (1.6” x 0.083”).
(For roll cages/bars approved prior to 1.1.95).
(b) Optional tubular members
38 x 2.5 (1.5” x 0.095”) or 40 x 2.0 (1.6” x 0.083”).

As far as I can make out the side impact tubes are optional members so 38mm should be OK.
However there is no mention of a petty strut - ie single forward brace anywhere in the regs or drawings. The nearest reference I can find is in K 1.3.3 " Forward facing stays are permitted if an angle of 30° cannot be achieved with Backstays, providing they do not unduly impede Driver and Co-Driver access" .
So would a petty strut be regarded as a forward stay? If so then would it be an optional fitment and therefore 35mm or mandatory and hence 45mm? Also there is an immediate problem as a petty strut would lay at approaching 60 degrees to the vertical - contravening the 30 degree rule.
Does anyone have any experience of petty struct fitment and approvals?

Thanks
Rich

[Kingster]

Moved this to Speed Series section @Rich Vaughan as it’s likely to get more response here 👍

[Mark (smokey mow)]

Is it a cage built to the tube dimensions in the blue book or a homologated ROPS?
 

If it’s the latter then you need to consider section 1.2.2. of the safety regulations

 

“ Any modification to a homologated ROPS (other than fitment of Roof Reinforcement, Windscreen Pillar Reinforcement, Doorbars and Harness Bars) is prohibited”

 

 

[Terry Everall]

Can you post a picture of the current roll bar including joints and backstays 

[maurici]

1 hour ago, Mark (smokey mow) said:

Is it a cage built to the tube dimensions in the blue book or a homologated ROPS?

This is the key of the question. However as far as i remember the westfield rear hoops are normally as per blue bookd dimensions rather than individual homologation.

[Rich Vaughan]

6 hours ago, Chris King said:

Moved this to Speed Series section @Rich Vaughan as it’s likely to get more response here 👍

Thanks Chris👍👍

[Rich Vaughan]

1 hour ago, Terry Everall - WSCC Competition Secretary said:

Can you post a picture of the current roll bar including joints and backstays 

Terry, the ROPS is I believe a Play Skool MSA standard one I bought second hand. I think their ROPS are built to blue book spec but not homologated

[Rich Vaughan]

3 hours ago, Mark (smokey mow) said:

Is it a cage built to the tube dimensions in the blue book or a homologated ROPS?
 

If it’s the latter then you need to consider section 1.2.2. of the safety regulations

 

“ Any modification to a homologated ROPS (other than fitment of Roof Reinforcement, Windscreen Pillar Reinforcement, Doorbars and Harness Bars) is prohibited”

 

 

Thanks Mark, it's a PlaySkool ROPS which I'm sure although built to  MSA spec are not homlogated

[Terry Everall]

Looking at the blue book I can't see and reference to the use of petty struts as an approved set up. I will do bit more research

 

[Rich Vaughan]

I have this morning written to the MSA technical about this and sent them this illustration. I'll feed back when I get a reply as it might be useful info for others in the future.rops proposal.pdf

 

Here is a copy of my query:

I have a Westfield 7se which currently has an MSA specifiation ROPS fitted ie 45mm x 2.5mm CDS tubing with diagonal bracing and two rear supports. I am proposing adding some additional support and protections by way of a Petty Strut and side intrusion bars. I am doing this as I don't want the weight penalty of a full cage nor the expense. I have attached an illustration of my proposals.

I have read the relevant sections in Part K of the Blue Book, but this has raised some questions which I would like clarification on before proceeding.

1. The Petty Strut:

(a) Is this a compulsory or optional addition and whichever the case does it have to be 45mm od or can it be 38mm od tube. Also can it be removable in either case?

(b)1.3.1 Backstays states: "Forward facing stays are permitted if an angle of 30° cannot be achieved with Backstays" - the strut will lay at an angle greater than 30 degrees to the vertical is this OK?

2. Side intrusion bars - I'm assuming that these are probably optional but 1.3.5. Optional Reinforcement of ROPS. states:

The diameter, thickness and material of reinforcements must be as defined in
1.4.1. They must be either welded in position or installed by
means of demountable joints. Reinforcement tubes must not be
attached to the bodyshell.

The bars will be located one end on the ROPS ( see illustration), but the other end will need to be located on the chassis/bodyshell, can I do this? If not can I simply bolt the bars to chassis at two points?