Another RX7 in the mix

who me? what? rust! i know no such thing.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Quote
john vanlandingham

Can't be that rough. Ford and Opel and about everything else rwd have been turreted and 4 linked for 3 1/2 decades or longer in most of the world, we first did one back in 87, another in 90, Dana 30 and 4 link first in a Colt, then in a RX3.

Maybe, but I can't afford to lose an inch of interior space, since I drive the car everywhere and haul all of my gear in it. Loading the car is like playing Tetris.

I'd love to do shock turrets, but that'd mean having to get a tire trailer, which would mean having to rent a storage locker for it. Maybe later.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 02/05/2012 04:04PM by Pete.

more reasons why i have a trailer now!

So what length would be ideal if im planning on making it all from scratch, and dont much mind cutting things? Perhaps up to the middle support beam behind the seats?

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

I keep thinking the front of the beam is a good place to stop if one were to do an Escort 4-link, then you could plate the link box to the front of the beam with ease.

The links, if I'm remembering right, will work out to be about 24" long if you do this.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Quote
Pete
I keep thinking the front of the beam is a good place to stop if one were to do an Escort 4-link, then you could plate the link box to the front of the beam with ease.

The links, if I'm remembering right, will work out to be about 24" long if you do this.

Is the "link box" that middle support beam behind the seats?

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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 02/06/2012 12:59PM by MeCalledEvan.

The link box is the box you install in the car, one per side, when you put in a Group 4 Escort style 4-link.

Find the Group 4 Escort Prep Manual - you WILL find it here if you look for it, but to prevent search engine spiders from finding it, it's never linked - and check it out. Lots of good ideas in that book.

Then go to MAT.fi's Projects section and drool over the Toyota Celicas that they quite literally rebuilt from scratch, and notice what the rear suspension looks like.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

i look at those pics. Thats basically what i would like to do

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

I have the Ford Escort manuals already downloaded. I took another look at them.
I see what you mean by the link box. My hope was to incorporate that into a support structure at the bottom of my main hoop. I had the idea that I could make the mounting location strong enough there that I wouldn't have to create the whole box structure and use shifter boots to prevent mud from flinging into the cockpit.

Alex, me too man. Me too. If I don't get into racing R&D or car setup and tuning, that right there is my dream. And hey man, we're still young and dumb! No reason it can't happen!

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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

I do have a couple questions though.
I've noticed that everyone relocates the links mounting locations on the axle itself. What is wrong with the location of stock mounting brackets on the axle? Is it because of potential interference under greater suspension travel?

Also, pertaining to seat mounting (which isn't too vital at the moment since I don't have a seat or money for one), I haven't seen any seats be mounted to the cage itself. I know in road racing, that is practically a must for car feedback and safety. Is it just too harsh of a ride if done in a rally car.

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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

Update:
I figured out geometry for most of the members in my cage-to-be this past week and ordered tube yesterday. 2x20' of 1.75X.095, and 2 of 1.5X.095. I also got 1 of 1.0X.095 for seat mounts and a few non-critical members for chassis rigidity.

For the rear strut tower extensions, I'm trying to decide whether I want to use 6" diameter pipe, or make boxes for them out of plate steel.

I've been playing around with electronics some as well. I've been trying to get my turn signals to work. I tore into my turn signal combination switch and cleaned out all the connections. Put it back together last night and will see if that fixed the problem.
I'm also going to look into wiring in an e-fan today or this weekend.

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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

my rear diff input flange does hit the tunnel when i'm totally mashed. off jumps, hard dips when i'm going too fast. I have done some hammer work for clearance, but mostly I've just angled the flange down a bit by adjusting my upper links a bit longer. the (very very small) downside to this is that power transmission is a bit less efficient if the input and output aren't parallel.
I use the buzzing sound it makes as a warning. it might happen once per rally. If I got much more compression travel, I'd end up crushing the gas tank.

For adjustable top shock mounts in the rear, I've thought of a quick way to run it. If I have time I'll CAD it up.

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"I put the hurt on dirt" - adam crane
http://CraneRallyCrew.com
corolla gt-s "Patches"
Op: S.S.

I guess I'll have to wait and see if I face the same problem. Doesn't sound like it is as big of an issue than what I assumed from hearing Jack. I won't have the risk of crushing the gas tank either since it is mounted behind the diff in the FB.

That's an interesting idea. I'm guessing that with it, you would have to leave the top of the strut "boxes" open to accommodate for the adjustable capture. Wouldn't this make them more susceptible to crushing, since you would be removing a structural surface that provides rigidity?
Also, I'm curious as to why you decided to run a square tube as your rear strut brace. Did you have a particular reason for this?

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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

Gas Tank - behind the diff doesn't mean attached to the diff (same in ae86). pull the springs and shocks off the rear, I bet the car will the ground at the same time the fenders hit the tires. if the road is rutted, the tank will take the hit. the diff is always going to be the same height off the ground.

Rear towers - This is something I was thinking of doing on 'hatches'. mostly because I may have a rear shock with an external reservoir.
the shock mount has one job - take the force of the shock in relation to the chassis. It can do that job better if it's tied to the cage. If you get your geometry right, the forces are pretty much "straight up" through the shock shaft, which should stay in a pretty small "cone".
Square tube has two (four) flat sides. flip it over, no alignment problems. easy to fabricate.
since the bar is attaching one tower to the other, there isn't much force in it (until the tree hits your shock - sideways). Strut braces are just that - For struts. rear shocks don't have the same problems as the engine bays of sentras.
the crushing you're worried about would be more of a problem of ripping the base of the mount from the trunk floor. there's more force from the car bumpstopping the landing of a jump then the axle dropping full stop in mid-air. The two bolts holding the cross bar have some of the job of the force, and would direct it "straight down" the open pyramid mount. It would focus the action on a smaller area (the bolts and metal below them), then the perimeter of a full enclosure, welded all the way around the trunk.

Pro:
adjustable up-down and inboard-outboard by flipping/fab-ing new crossbar.
ease of installation and inspection.
pass through area for remote reservoir.
in a crash anything that didn't rip your axle from under the car would have to travel further to adjust your shock mount.

Con:
Heavier (depends on how you do it)
more bolts.
dirt city (I would seal it with zip up snowboard pants, glued/riveted to the "tower"
complex.
un-necessary - once you have your shocks picked out and (carefully) fit, you shouldn't need any adjustment.
forces focused on goose-neck, 2 bolts, and smaller base area.

Full enclosure (tube or tower)
Pro:
lots of landing area for the rear stays of the cage,
keep out the dirt,
robust,
simple.
lots of load path for shock forces.
Con:
hard to lift the shock and line up the bolt (get JVAB heim reducers or a helping hand from a friend)
topmount location is now adjustable by sawzall.
where to put that remote reservoir?
spring adjustment?

Now I want to CAD it more than ever.

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"I put the hurt on dirt" - adam crane
http://CraneRallyCrew.com
corolla gt-s "Patches"
Op: S.S.

Gas Tank: I didn't think of that. The FBs is recessed up into the underside of the chassis a bit. I'll have to look into that.

Rear Towers: That's a cool idea, but there does seem to be some unnecessary complexity. Especially for me since I'm still way in the learning process of all this.
A simpler way to make towers with adjustable top eyelet pickup points could be to fabricate the towers "a la" the extended upper trailing link boxes. Then drill a couple sets of holes through the sides at different heights. Slam a bolt through the eyelet and whichever hole you would want to use. Yeah?

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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

If you wanted to do something like that, keep the shocks mounted off the end of the rear instead of on top, and use drag racing style coilover axle mounts. Pre-fabricated and you have a ton of adjustability to play with. That way you don't have to worry about having 2" of spacer hanging off of each end of the upper eyelet, holding the shock in with a 5" long bolt.

If adjusting the ride height that much, that way, is even important.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.