Rotus 7 front suspension help...

Hi all, I recently got a 1990 Rotus 7 <woop!> It's been in the garage since I got it, after a lap around the block, up on stands while I wrap my head around it and give it a good check/refresh before another lap around the block. While bleeding the front brakes I noticed the front upper control arm bushings (bearings?) are shot, the ball joint end moves ~3/16" forward-to-back.  Also (at least) one of outer steering heim joints has some play. 

Wondering if anyone knows what's inside the control arm at the center pivot? Mostly looking for where to source replacement parts. Also wondering what the tightening torque should be on bolts at the heim joints, the upper bolt is likely a 5/8" thd and the lower a 1/2" thd. 

Here's a couple pictures (pay no attention to the wire nuts and scotchlocks installed by PO, yeesh)

I have no rotus specific knowledge, but would suspect that it's a bushing. You will probably have to disassemble, measure ID of the control arm and OD of you bolt and hit the Googles or have a new one machined. Same story for a bearing, but with better odds you can find a number stamped on it to find a replacement.

The bushing is probably off some common car, I think the UK cars use something from an Escort. Rotuses (Rotii?) have been around long enough, I'd check with the UK Locost or USA7s forums and see if someone knows.

Rod ends are a consumable. Get good ones and plan on replacing them regularly. I've used a lot of FK units. They come in many different grades, might be worth talking to a specialist about the best type for your application. You should also install a safety washer under the bolt heads so the joint holds together if the rod end fails.

Tightening torque for the bolts through the rod ends should be appropriate for a bolt of that size and grade. Given their size, it will probably be "nice and tight". You're not going to snap one and the rod end doesn't need any slack.

Is it an optical illusion that the teeter totter is bent?

In reply to bentwrench :

I hope so! The inner tubes are parallel, where the outer taper to he joint, and they're boxed underneath. But I'm going to double check!

Just don't set it on your Hootus.

I have all of the factory documentation from my car with part numbers for all of the "off the shelf" parts that were used.

One of the problems with the front suspension is the upper ball joint that you have circled in the first picture. All of the forces from front suspension movement and spring pressure act at the high-misalignment rod-end that is being used as your upper ball-joint. When you align the car and set the camber, the exposed threads between the body and jam-nut tend to "bend" over time. Most cars still use the stock Toyota ball joint which easily bends. I would guess that your set-up is a big improvement as the Rod-end is surely much stronger. On my car, I machined a much longer jam-nut to cover more of the threads. I've also spoken with others who have the same bending issue but don't have access to machinery to make the nuts so they simply double-up the jam-nut with good success.

The only reference in the parts list is for "suspension bushings(all)"      (Harris)64-A 62367

In reply to bentwrench :

They should be flat/parallel and not "bent".

Thanks! It's great to see/talk to another Rotii. Luckily I have a couple notebooks full of owner/builder docs also, but hadn't checked for these parts since a lot has been changed. Mine seems to have spent most of it's life on the track and was 'improved' in a variety of ways, including 3" longer A arms, longer rocker arms and custom spindles. The A-arm mounting at the frame looks the same as yours and so maybe the bushing P/N you gave will work - it appears to cross to a Moog K8042 or AC Delco 45G12003 (1962 Ford Fairlane idler arm bushing at the Center Link End).

When looking at the assembly from above I noticed the rear tube of LH lower control arm was closer to frame (front face of your radiator) than the RH. I can't see anything bent, nor any sign of impact so I spend much of yesterday with a plumb bob and tape measure checking for anything weird... When factoring in the fudge factor of me crawling around on the floor with a tape measure and a plumb bob most everything looks pretty good except the LF wheel is ~1/2" further back than the RF wheel... so I'm hoping the bushings are the cause, seems like a lot but...

I just ordered 8x bushings and a reman steering rack, looks like I'll be getting more intimate with this thing. I appreciate the assistance!

The above picture is from a car listed currently on Bring A Trailer. Mine is sitting in the shop waiting for the fuel tank to be reinstalled and a pinion seal changed. This summer will be fun as this will be my DD.

Old picture before clamshell fenders installed and a new rollbar fabricated.

That one on BAT is practically new, I might have to keep an eye on it... it wouldn't be totally crazy to own two of them, would it?!  The one I bought is pretty hard core and the motor is probably not going to like modern traffic, I'm pondering a modern duratec with individual throttle bodies...  but my head is kind of swimming as I've been learning about these cars for all of 3 weeks now. Again, I appreciate the input!

Edit: Holey crap that one is less than 5 miles from me!

I came very close to bidding on the purple & black car on BAT a bit ago... is that the one you ended up with? I'll have to keep my eyes open for you when you get it in the road - I'm at William Cannon and Manchaca 

In reply to Espartan (Forum Supporter) :

Howdy neighbor! Yep that's me, I hope to get it out for another lap around the block once I get the front end sorted in a few weeks <fingerscrossed>

@hayduke, What did you end up ordering for bushings and how did it turn out?  I have the lower rear links on mine disconnected at the moment and am staring at the same bushing (as suggested by the parts list).  Also, did you reuse the all-metal stop nuts?  They appear to be softer than the bolts and thus fine to reuse, but I am cautious about unknown hardware.

Now contrary to the parts list, the panhard bar uses a different bushing.

The bush is two identical rubber ends sandwiching a metal spacer which appears to be a permanent part.

While all these could do for a refresh, my real motivation was to rotate the nose of the diff down to access the pinion flange; as the flat floor blocks access to the pinion nut.

Howdy @mn01752 nice to see another Rotus!  I haven't tackled the rear yet, but I'm assuming the rear links use the same bushing as the front... I cross referenced the numbers in the parts list and came up with AC Delco p/n 45G12003 from Rock Auto 

There's a little more info here...https://grassrootsmotorsports.com/forum/grm/replacing-bushings-in-tubular-control-arms/189862/page1/

After doing the fronts I'm thinking of exploring something like this if I tackle the rears... https://www.summitracing.com/parts/paj-1206-5-8  rather than trying to replace the old bushings. I'm not sure what "the all-metal stop nuts" are but I replaced all the hardware up front. Mostly because this was a race car and I have no idea what (care/abuse) they've seen. If they've been there since new I'd consider reusing.

And the panhard bushing looks like an old-fashioned shock absorber mount bushing, Dorman has a variety of sizes.

As for pinion access, have you tried from above? Mine has a sheet metal cover over the driveshaft, between the seats, I had it off when replacing the trans mount and there may be better access to the diff from there.

I took a deeper dive into the suspension (plus a few tangents) over on the locost forum...  https://www.locostusa.com/forums/viewtopic.php?f=5&t=21528 

Good luck!

Chris Custer (Rotus manufacturer) didn't do the design work himself, he farmed it out to a proper suspension engineer, who I'm still friends with. If you have specific suspension questions, I'll pass them on. Just keep in mind that it's been a long time and he may not remember all the details.

You can thank me by buying one of my books :)

Hi kb, actually you replied to a similar thread on the locost site back in January, is your friend Dennis? I've been slowly learning the history of these cars and the 'pedigree' of mine, which was built/raced by Frank Nolfi  in the 1990's. I've seen several references to him, Chris and Dennis working together back then. 

Thankfully Frank took meticulous notes, mostly on the engine, but there is a note from July '95... "RF spindle broke, LF cracked, installing wide track".  

Any info on the wide track suspension would be interesting, if nothing else just thank him and let him know his work is still appreciated! I've got the suspension back together, with more adjustability, and my initial on the garage floor alignment looks like a good starting point.

Actually a specific question is how to calculate the spring and wheel rate with the inboard springs, I haven't found an online calculator that deals with inboards.

And I've added a book to my christmas list! 

Thanks!

Stover nuts - an elliptical metal stop nut.  

Except for the panhard rod, all the suspension links on #57 are attached with ⅝" stover nuts.

I hadn't considered tackling the pinion from the top!  I believe on my car the skins are riveted in place; but if not, this is likely the easier route.

Thanks for the tip on bushings.  We do have a press in the shop which should make short work of them - especially without the complexity of the front links you faced.  The current bushings are seized and I can imagine the combined stiction of the eight bushings on the four rear links add to the spring rate in the rear.

Hayduke said:

Hi kb, actually you replied to a similar thread on the locost site back in January, is your friend Dennis? ...

Actually a specific question is how to calculate the spring and wheel rate with the inboard springs, I haven't found an online calculator that deals with inboards.

And I've added a book to my christmas list! 

Thanks!

He goes by Lee but is mentioned in the Rotus magazine article as Asher. At one time I was seriously interested in buying a Rotus back when they were being manufactured. Even talked to Dennis a few times and checked out one in the Reno area. It wasn't so much the car that concerned me, but the way the business was run... enough said about that. As for the suspension ratio, I seem to recall it being 1:1. It's easy enough to find out. Remove the spring (to make things easier) and compress the shock by 1", measuring how much the wheel spindle moves. Compress the shock another inch and repeat, charting the results.

Decades ago I started a new job at an aerospace company. During a business trip, I got to talking to a fellow engineer about cars, and mentioned offhand that the only kit car I really like was the Rotus. He looked at me oddly and said "I designed that!" That was the beginning of a long friendship. I'll let him know that people are still running and working on the cars - and thank you about the book!

Oh, and you asked what's inside the rocker arm pivot. I can ask him but think it uses spherical bearings.

In reply to mn01752 :

Thanks for the nut info, I'm a visual learner :o) McMaster has 'Distorted thread' nuts...  I think I read that type of nut is OK to reuse if the threads are still able to bind on the screw... if it threads all the way with little effort, toss it. Pegasus racing mas a pretty good selection of hardware also.

Here's a pic of the mcmaster 5/8-18 distorted nut, I'm using nylocks for now as I anticipate taking it all apart at least once more

In reply to kb58 :

Neat story!  As for the ratios I was trying to ask about calculating the spring rate/wheel rate, it occurred to me that if the rocker arm has equal lengths from the fulcrum it's 1:1, so a 350# spring would exert 350# at the wheel - I think. But doesn't the angle of the spring relative to the rocker come into play? This isn't critical to anything in particular, I'm just trying to get a better understanding of what's what.

I already learnt about the insides of the rocker pivot, it uses the same bushing as the lowers (1962 Ford Fairlane idler arm bushing) on the ends with a steel spacer in the middle. Or at least mine does. 

Those Heim joints should have safety washers on them to retain the rod end if the the joint fails.

APEowner said:

Those Heim joints should have safety washers on them to retain the rod end if the the joint fails.

Good catch and thanks, that pic was 'as-delivered', safety washers on all of them now.

This conversation inspired me to send Dennis an email asking if he had any recollection about my car; as the story goes it was used for a press event.  He responded quickly and confirmed my car was the first Turbo II and was driven to the Chrysler Proving Grounds in Michigan and spent a few days with Csaba Csere of Car & Driver.  I suspect this was used in the March 1990 issue of the magazine.  I've found a copy and look forward to reading it when it arrives.

Dennis confirmed he has the jigs and molds for the car and can reproduce parts.

My favorite line from the email, "Your car made the naturally aspirated car look like a yard ornament, so much quicker.".

The list of media references I have found for these cars includes the following.  I am curious if others have additional references.  I am missing copies of the 1984 Kit Car and 1985 Autoweek articles.

"The Sweet Rotus V-8"                          Car & Driver Magazine    March 1990
"Active suspensions and other atrocities."    Brock Yates        August 1988
"A Corvette Stomper from Maryland"    Rob St. Francis    STOPWATCHER    
"WHAT A SPORTS CAR IS SUPPOSED TO BE"    Brock Yates    Washington Post. ISSN 0190-8286    8 November 1987
"Rotus Buildup Part 3"    Dave Fults    Kit Car Magazine    
"Rotus Buildup Part 2"    Dave Fults    Kit Car Magazine    January 1987
"Rotus Buildup Part 1"    Dave Fults     Kit Car Magazine    November 1986
"Driving Impression" ROTUS SEVEN"    Dave Fults    Kit Car Magazine    
"The Rotus Seven"          Peter Egan    Road & Track    
"1985 Rotus 7: Custers Last Stand"      Autoweek    11 March 1985
"Retro Review: '84 Rotus 7"                  Motorweek    1984
???                                                             Kit Car Magazine    1984

I did learn from scanning the articles that replacement Lotus Seven frames produced by the company are likely serialized in the number sequences we see in the VIN of our cars.  So the 93 (the highest number I have run across) or so chassis are Rotus cars and replacement chassis combined.

just ran across this thread...find it interesting you mention #93... I OWN that car ser #93 that is.

I have a copy of the 1984 kit car magazine ( bought in 1984) wi the Rotus article you mention you are missing.
I could scan a copy if desired.

My biggest issue with #93.... no documentation. I'm flying blind trying to find parts for it. I've seen a couple lists now, but none seem to match my car.
Any help would be MASSIVELY a[appreciated.!

Paul Tegler