M20 Dreaming

[Russ Noble]

My guess (being a kiwi) is they would have rang the local hardware store and said " what have you got that will glue alloy sheet"

Don't forget Bruce had an engineering degree so was streets ahead of most of us to start with. I'm picking everything would have been backed up by calculations and I would venture that he would be more likely to be quizzing someone in the aviation industry rather than his local hardware store.

Carey Taylor was heavily involved in the McLaren CanAm program. He would know for sure how they were done in the day. He's still around here in Chch. I'm sure he would be very helpful if you were to contact him.

 

[Leon]

Hi Russ, Of corse you are right, I was just making a point that with all the choices out in the market today it makes the job so hard to choose the best thing, back then they were more limited in chioce and as you say, the Aviation industry was the best source of information. Is there any chance you could fine a contact or talk to Carey Taylor, it would be great to know for fact what they used.
Mikky, the grade of alloy is 5052 and its 1.6mm, if you are talking to you man at the Aviation ficility it would be good to hear what he says.
Cheers Leonmac

 

[Jac Mac]

Just in case you decide to do it proper like!! Check out ---M C Gill Corp------- on google

 

[Leon]

Very nice stuff, Wouldn't like to guess what it would cost here in NZ, I didn't see any thing on the adhesives they used, Maybe I wasn't looking in the right area.
Thanks Jacmac.

 

[Leon]

After Reading all the information that has come forward on the bonding of Mono tubs it has really given me some insight into how this task is to be done. One of the most helpfull things that has come from this is the sites that verious people have alerted me to and the information those sites have provided, So a big thanks to you all.
I'd like to thank Mickky3 for all the stuff he has sent and it has shown me alot about the riveting process which has changed my line of thought on that, so at this point its Adhesive (sikaflex) and a lot of Double row riveting and a Lot of Double and Tripple laminate area's around the high stress area's.
Cheers Leonmac

 

[Terry Oxandale]

I guess we'll be seeing photos of this process soon!?! wink wink nod nod

 

[Leon]

Will be a few weeks yet but hey NO pressure right.

Cheers Leonmac

 

[Leon]

Heres a question for Russ and Terry, what type of rivets did you or are you intending to use. I have done some research into this and have come up with 3 different types that I will probably use. They are the comon Pop rivet (Non structural) an "SR Series" Structural rivet 700lbs shear and 500lbs tensile. which I will use for the bulk of the job and the "CherryMax" CherryLock Aviation spec rivet which I will use on all the suspension brackets, around the steel bulkheads where the engine mounting plates and tri pods attach, I see these as being the main high load areas. As you would expect there is a considerable price difference from the "Pop" to the "CherryMax" NZ$ 34.00 for 500 Pops, NZ$200.00 for 500 SR Series and NZ$ 600.00 for 500 CherryMax. As I'm expecting to use more than 1000 rivets you can see why I'm only useing the CherryMax where I think its really needed and will use the SR pretty much every where else. Your thoughts Please. Cheers Leonmac

 

[Russ Noble]

Hi Terry,

I just used the non-structural pop rivet. It's main function in my build is to hold the panel until the adhesive cures.

As a matter of interest my rear bulkhead panel is attached to the roll bar. MSNZ will not entertain holes drilled into the roll protection structure so in this case it was just clamped in place with lengths of wood and G clamps etc until the Plexus was well cured. It's solid as a rock even though it is bonded to round tube. It braces the rear bay and who knows what sort of loads have been fed into it with some of my escapades last season. Fortunately non of the upside down variety yet though......

I've got a damaged/bent chassis tube on the bottom of the car this has crunched the aluminium panels but neither the Plexus nor the rivets appear to have let go. So I've decided to leave it as is until the chassis needs a major rebuild. Theoretically it's not ideal, but in practice I don't think it makes a lot of difference.

 

[Leon]

Hi Russ, Interesting you mention about holes in the roll cage, My roll bar is going to run down on each side of the rear bulk head. It is located in 50x50 box section and I was either going to drill through and put bolts right through or I was going to weld a peice of 2" pipe in the Box section that will sick up 100mm and bolt through to hold the bar it would then be braced back onto the engine block. This is the preferred choice as I will be able to get to the bolts once the Bulkhead is paneled in. Are you saying that I would not be allowed to attach the Bar by this method. This how a lot of the Can-Am cars were done as it allows for the Bar to be removed without having to pull the Monocoque to bits. Cheers Leonmac

 

[Terry Oxandale]

I agree with Russ in regards to the rivets for my specific application, and his testimonial on the damaged tube still holding the bond reinforces that.

I don't know the answer to the roll cage/hoop issue, but back then, the rules were much less "safe" than they are today. I suspect the new rules will be what the tech inspection will be based on, being this car will not be historically grandfathered in. I've also been thinking this through as I've planned on "bolting" the main hoop into two tube stubs with the top supported back to the framing just aft of the motor.

 

[Leon]

Hi Terry, I know we used to be able to do the tube stubs with bolts through in the roll cages for rally cars and I think because you have double the tube thickness in this area is why it was allowed. I will have to check the MANZ regs and see what going on, other wise I will just weld it into the boxsection and be done with it.
Cheers Leonmac

 

[Russ Noble]

Hi Russ, Interesting you mention about holes in the roll cage, My roll bar is going to run down on each side of the rear bulk head. It is located in 50x50 box section and I was either going to drill through and put bolts right through or I was going to weld a peice of 2" pipe in the Box section that will sick up 100mm and bolt through to hold the bar it would then be braced back onto the engine block. This is the preferred choice as I will be able to get to the bolts once the Bulkhead is paneled in. Are you saying that I would not be allowed to attach the Bar by this method. This how a lot of the Can-Am cars were done as it allows for the Bar to be removed without having to pull the Monocoque to bits. Cheers Leonmac

I don't think you would be able to mount the main rollbar that way these days. I think there is some shit presently going down about the original roll bars that are still in some historic cars. You could always email MSNZ Tech to check if it would comply.

MSNZ have a standard spec that you must adhere to to get your roll protection homologated. You can either do it the way they stipulate. Cheapest and easiest. Or you can do 'Alternative Design (Free Concept)' and have it certified by an engineer that it will resist the forces they stipulate ie: 1.5W lateral; 5.5W fore and aft; 7.5W vertical. Where W = (weight of car +150Kg)

The roll protection regs are really saloon car based and don't particularly cater for spaceframes or alloy singleseater/sportscar monos. However if you make a few compromises to accomodate their design your homologation approval is basically rubber stamped. Which is what I did.

Weld a plate of the minimum dimensions (>120sq cm, and if needed with captive nuts under) , on top of your 2" box, maybe to be hidden under your alloy panelling. Weld a foot (3mm x 120sq cm) on the bottom of your rollbar and attach with three 8mm ISO 8.8 bolts and you'll comply no hassles.

My main rollbar is not removable. I welded a plate of the correct dimensions to my spaceframe and welded the rollcage to it. The plate doesn't do anything but it complies with their regs, so rubber stamp! LOL.

MSNZ safety regs (Schedule A) are online here http://www.motorsport.org.nz/assets/MotorSport-Manual/App-2.02-Sch-A-2010.pdf and the rollbar diagrams are on the last few pages

 

[Andrew Robertson]

I don't think you would be able to mount the main rollbar that way these days. I think there is some shit presently going down about the original roll bars that are still in some historic cars. You could always email MSNZ Tech to check if it would comply.

As a side note, no hinge joints are allowed in the principle structure either - this means regardless of how compliant you are in mounting the main hoop, if your rear stays are hinged so you can disconnect them when you lift the rear body work then you need to go the "free concept" route and get the cage engineered. This is what I am doing. You can see in the photo where the rear stays mount to the top of the main hoop and the rear bulkhead just ahead of the rear anti-roll bar - I am using massive rod-ends in 3mm double shear with stout foot plates and 38x2.5mm roll cage tube for the stays themselves but it will still need to be engineered. Cheers, Andrew

 

[Russ Noble]

Andrew that's fine if you've got a tame registered engineer.

The other alternative, which I have done with my backstays, is very neat and tidy as per Drawing 253-28 in Schedule A

Edit: Ah, but now that I've read your post again 253-28 won't work conveniently if the stays have to be removed frequently to enable body fitment. One of my Brabhams used to have 'pip' pins in place of a bolt on the rear stay. Almost instantaneous removal. Not sure how that would fit with the regs these days....

 

[Leon]

Hi Russ/Andrew
I sent an email to Leon in CHCH and he sent me a link to the MANZ specs for the Roll Bar/Cage designs and I'm pretty sure what I'm planning will be legal. I may just have to put a foot at the bottom of the Bulkhead where the foot of the hoop sit's and I could weld the back stays and have the whole thing drop down on the engine and bulkhead as I don't need to remove the stays to remove the rear body work.
I will get the local Scrutineer to check out what I'm doing to make sure.
Cheers Leonmac

 

[kiwi ka]

Leon
Just an other option, one I copied from Leitch Motorsports and have had certified on my McLaren `McCopy`. This way either rear support bars can be removed individually, the roll bar end connection is the standard MANZ tapered one with a 10mm cap screw up the centre and the rear tube end is a turned tapered steel part fitted with a 1/2 inch rod end to the chassis attachments which are 2 x 3mm plate and that attachement point is behind the rear axel centre line with their full knowledge and approval. When they saw and understood the design / strenght of the chassis, there was no issue...its not a Subaru rally car was fully understood.
Cheers

 

[Leon]

Hi Russell,
The 10mm cap screw at the roll bar end, is it going through a boss welded in the roll bar and then into a plug welded in the end of the back stay, am I reading it right. its easy to see what you have done at the other end with the rod end but not so easy to comprehend what is at the roll bar end.
Thanks Leonmac.

 

[Terry Oxandale]

I second that query. A shot of the main hoop's connection to the frame would be very helpful.

 

[Russ Noble]

The other alternative, which I have done with my backstays, is very neat and tidy as per Drawing 253-28 in Schedule A

Leon and Terry, 253-28. This is what Russell has done. There is an excellent drawing in Sch. A

MSNZ safety regs (Schedule A) are online here
http://www.motorsport.org.nz/assets/MotorSport-Manual/App-2.02-Sch-A-2010.pdf
and 253-28 is at the top of the second to last page