Rotus

[RV8a/Stalker]

Anyone have a Rotus?

Do you need any info/help?

Well its your lucky day, I work with the designer.

Contact me off line.

[JohnCh]

Not sure there are any Rotus owners on here, but there are a few who post on USA7s.

-John

[slngsht]

Would that be Lee?

I'm afraid he won't be able to help me much with my Rotus anymore :D

[RV8a/Stalker]

Yea thats him, your response sounds interesting, anything you want to discuss back channels?

[JohnCh]

I believe Slngsht was referring to his car’s slight transformation from the original design ;) Details are available here.

-John

[soareyes]

Yea, I think the car's nickname 'Franken7' says it all...
:)

Stan

[RV8a/Stalker]

Reminds me of an airplane that had a Franklin engine installed which did not fit as clean as the previous engine..........they called it Franklinstien.

[slngsht]

The engine retrofit actually required VERY little modification of the chassis.

It's what happened two years later that slightly altered things.

Rotus had the tank in front of the rear axle. While I really liked that design feature from a safety perspective, I decided to move pretty much everything back in the car, so the driver's butt now occupies that space. Engine and transmission both moved back several inches, as did the passenger compartment and the roll bar. The entire trunk area was redone, as well as the entire tunnel, dash area, and roll bar. With these changes I think I will achieve a rear weight bias (I have measured each component individually, along with location in the chassis, and estimate a 47/53 F/R weight distribution).

Another motivation for the big move was that like most sevens, mine had the hanging oil pan problem, preventing me from lowering the car. I moved the engine and tranny up into the chassis, and now have the entire car lowered. Looking at the bottom of the car, now you see one flat sheet of aluminum with nothing hanging down. The ride height is now 3".

I changed the front suspension (by now Lee will be rolling his eyes and shaking his head. LOL ). I thought the brakes in the rotus were marginal for its performance potential. Many routes to upgrade... I decided to go with C5 uprights and brakes. One thing that concerned me was that Rotus' cantilever upper Aarm setup transmitted suspension loads through the upper ball joint, which my upright - as well as most other uprights - aren't designed to do. So I went back to a traditional outboard spring. I don't have the rising rate suspension anymore. Once my final setup in the front is done, it will be less than 10% effective spring rate change through its motion range.

That's pretty much a summary of what I've done to it. Of all the original parts on the car, the radiator and its fan are still there, as well as steering rack. The bottom plane of the frame, as well as all the tubes for the front suspension and the engine bay are still original. Pretty much everything else is changed.

[RV8a/Stalker]

You mentioned the oil pan.......I am making a baffled pan right now for my L67. I know the pan touched a speed bump once, and obviously has happened more than once but I could not tell when it happened the other times.

The pan will be 1.5 inches shorter and fully baffled with doors so no matter what the G's are doing to the oil, it will have no choice but to flow towards the pick up.


You said you raised the engine and lowered the car........how does this work exactly. On my car I set the lower A arm horz and the tire with 0 camber. Lower the car until there is 1/2 degree tire camber and that is the sweet spot on the front suspension. I would imagine all 7 type cars are near this setting? Are both of your A arms significantly angled upwards? How is this correct in the suspension geometry world? Not an attack on you just trying to pick your brain:)

[slngsht]

I still have alot of playing around to do to set the front suspension. I just got the car running again, and still have to remake the front Aarms - my original design last year ran into a slight interference at the limits of steering. Rotus' original Aarms are straight on the back side, and I went with the same design, but with my wider wheels, when I turn the wheel all the way, the inside of the wheel would rub against the front of the Aarm, which obviously needs to be fixed. I need to make symmetrical Aarms to cure that problem.

To answer your question, yes, my lower Aarm would be slightly angled at ride height. I can't remember off the top of my head what the angle is, but the outer end is 1.5" higher than the chassis end IIRC. I plan to start with no more than 1 degree static camber, and about 5 degrees caster, and use tire temps to guide what I do from there.

I ran the numbers about 2 years ago when considering all this, and again, if i recall right, my camber gain improved with the lower aarm angled slightly up (chassis end lower).

As for the oil pan, I could've gone with a dry sump system, but after driving the car for 2 years I realized that even though the pan was the lowest point on the car, most often I would hit the bottom of the bellhousing on speed bumps.