Another RX7 in the mix

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heymagic
Yes, put the main hoop way back on the shelf and not the actual floor. You can lean it back 10* also if needed.

Yeah so far back the backstays are at some "great" angle...oi!

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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pdxphil42

I think you'll find that with a race seat, you'll have a lot more flexability. The stock RX7 seats put you pretty far off the floor. It is a tight fit though. I've got my seat set pretty far back, almost to the main hoop.

Definitely flexability more than if I were 6'2"! One of the few benefits of being pretty short.
It'll be interesting to start trying seats out. I've only sat in 1 or 2 bucket seats in my life.

JVL - You've lost me.

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011

Ya he lost me too...

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heymagic
Ya he lost me too...

If you move the main hoop waaaaaaaaaaaay back AND intend to have the backstays actually brace the main hoop and run the backstay tubes to somewhere half reasonable you could end up with a really steep angled back stay, like way less than 45^o.

Fat lotta good they'll do just a couple of inches back from the main hoop and nearly straight up....

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Ok I thought that may have been what you meant, after I gave it some more thought. Yeah that makes sense.

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011

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john vanlandingham

Quote
heymagic
Ya he lost me too...

If you move the main hoop waaaaaaaaaaaay back AND intend to have the backstays actually brace the main hoop and run the backstay tubes to somewhere half reasonable you could end up with a really steep angled back stay, like way less than 45^o.

Fat lotta good they'll do just a couple of inches back from the main hoop and nearly straight up....

Cage doesn't do anyone any good if they can't fit in the car....
The backstays can be dropped on the main hoop a bit and they can be located a bit further back on the inner fenders.
The purpose of a cage is occupant safety not suspension mounting.

More steps closer to a point cloud. Not ready for sharing yet though.

Pete, those photos are helping immensely! I noticed that it looks like you cut out all the inner skin in your ceiling. Is that the case and is that something you would suggest doing?

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011



Edited 1 time(s). Last edit at 01/25/2012 11:48PM by MeCalledEvan.

Today I got my point cloud measured out, mocked up with tape and cardboard, and drawn up in CAD. Here is my first revision of my cage design. I think I have some of the measurements and geometry around the doors/front downstays wrong and will need to double-check them. I also need to measure the suspension mounting points and redesign them to have a panhard bar and parallel trailing links.

Note: This design is currently with the stock rear strut tower height. I am not sure how much higher I should box the towers yet, but that will be easy to alter in my design.

How should I go about having a scrutineer analyze my design before I start constructing it?

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011

Where do the backstays connect to? It looks like they come together as a inverted V and connect to the mid point of the top of the main hoop?

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"I, for one, welcome our Robot Overlords." - Philip J. Fry

If you grab a copy of the FIA Article 253 App J: AppJ Art 253

My RX7 is done as such:

Main structure: 253-3
Diagonal member: 253-7
Door bars: 253-9
Roof re-enforcement: 253-14
Windscreen pillar re-enforcement: 253-15
Backstay diagonals: 253-22

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"I, for one, welcome our Robot Overlords." - Philip J. Fry

Phil,
I've got the regulations and have gone through them.
Like you, I'm using---
Main structure: 253-3
Diagonal member: 253-7
Door bars: 253-11
Roof re-enforcement: 253-14
Windscreen pillar re-enforcement: 253-15
Backstay diagonals: 253-22
Strut bar: 253-18
Further strut reinforcement: 253-17 (still unconfirmed)

I forgot to add in the side of the backstays, so you're right, for this photo, they are just an inverted V. I was shooting for 253-22 in case I ever have to crawl out the back hatch, I don't have to circumnavigate 2 Xs (253-7 and 253-21).
I decided to go with 253-11 because I think with 253-9, my funny bone would become great friends with the door bar, which I don't really want. Doesn't seem like much fun.

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011



Edited 1 time(s). Last edit at 01/27/2012 03:06AM by MeCalledEvan.

Evan, WHY would you do the inverted V with the backstays rather than at the sides, and diagonals?

Doesn't that corner, right where we often land, look awfully unsupported to you??

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Ok...
You cannot have that many bends in the main hoop. Looks like 7 to me, needs to be 4.
You need conventional backstays from the main hoop outside bends.
Your door bar configuration doesn't make sense. The mass of your body and vital organs are just in front of the main hoop . You have virtually no side protection there.
You would have to be one of the Fantastic 4 to squeeze between the seats and out the hatch of a wrecked RX7....

Phils cage is what you should be looking at, forget the cloud points, CAD and etch a sketch. Get a tape measure and piece of chalk.

Quote
heymagic
Ok...
You cannot have that many bends in the main hoop. Looks like 7 to me, needs to be 4.
You need conventional backstays from the main hoop outside bends.
Your door bar configuration doesn't make sense. The mass of your body and vital organs are just in front of the main hoop . You have virtually no side protection there.
You would have to be one of the Fantastic 4 to squeeze between the seats and out the hatch of a wrecked RX7....

Phils cage is what you should be looking at, forget the cloud points, CAD and etch a sketch. Get a tape measure and piece of chalk.

Gotta agree.
In some things, CAD is a nice aid....For example right now, today, I gotta figure a way to put TWO sets of boltholes for pressure plates in some steel flywheels Each has 6 holes tapped M8 and 3 plain 6mm holes for locating pin. It occurred to me That I have to "clock" the patterns so I don't end up with holes overlapping or the 6mm pin holes disappearing down some 8mm hole..

Easy with CAD. And I don't have to go out in my fawkin freezing garage..

But I could do it with the physical parts.

In the cage realm, every step taken away from the car towards a keyboard is a step away from having a cage in the car..

The CAR, real physical thing, is the CENTRAL thing, not opinions , not anything. The RULES come next, the cage must satisfy the rules but it must FIT WITHIn the CAR. And leave some sort of tiny cramped, annoying and ultimately limited space for the poor bastids who will be crammed in there.


Evan, Your signature posits a seriously erroneous idea with relevance to this first basic step of the cage---which we see has veered away from the point of the cage and reality...
Your siggy:
My life as an engineering student, stated by my friend Joe:

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"We were brainwashed in elementary school to think that making assumptions makes an ass of you and me, and that's crap.
As engineers, we make assumptions, check them, and if we're right then we're geniuses"

You and Joe were not brainwashed. Your friend Joe was not smarter than those who obviously did not manage to teach him well enough..they may not have been smarter, but they had experience, an often good substitute for intelligence.
A usually good substitute.

Cutesy homilies aside, assumptions are the root of most blunders.
Assumptions in small details, assumption about the main purpose of doing things, about our own abilities, everything.......

The part that is particularly flat wrong is "we make assumptions, check them and if we're right...."

No that's what lifetime students with unlimited funds and who never need to get anything done do...

Engineering is not about "making assumptions"...

I have to go work on some actual physical things made of steel and bronze, but this subject is one you should explore ---with an open mind and with a broader question "What is the MAIN POINT I am trying to accomplish?" in mind.
Exploring this one fundamental error could be the most important thing you do at college.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
heymagic
Ok...
You cannot have that many bends in the main hoop. Looks like 7 to me, needs to be 4.
You need conventional backstays from the main hoop outside bends.
Your door bar configuration doesn't make sense. The mass of your body and vital organs are just in front of the main hoop . You have virtually no side protection there.
You would have to be one of the Fantastic 4 to squeeze between the seats and out the hatch of a wrecked RX7....

Phils cage is what you should be looking at, forget the cloud points, CAD and etch a sketch. Get a tape measure and piece of chalk.

Gene:
I had forgotten the 4 bends in the main hoop and was trying to follow the curvature of the body. That is an easy remedy.

I replied to Phil commenting on the backstays. I had just forgotten to add them into my CAD model.

As for the door bar, I'm small enough and need to sit forward enough in the car that I still have side protection from that design. Maybe not enough though and I will look into that further.

Egressing out the back hatch, although difficult, would be made completely impossible with 2 X-patterns. I don't see why the inverted V would not function just as well.

I did the tape measure thing yesterday and mocked up Gene's design with masking tape. I can't draw well at all, all my attempts at sketching a cage look like shit, and so CATIA has been my chalkboard.

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"The more I learn, the more I realize I don't know and have so much more to learn." - Claude Rouelle, Optimum G lecture June, 2011