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PostPosted: January 7, 2022, 8:21 pm 
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Joined: January 7, 2022, 9:53 am
Posts: 45
Location: Buda, Tx
Greetings, first post here, lurked many times over the years, an amazing collection of people and machines here!

Back in November I had a mid-life-crisis moment and bought a 1990 Rotus online. I've always loved 7's and while I also wanted to build one, approaching 60 I decided this was the better route. So I got it shipped to me and the total sum of my driving experience in a 7 was a trip around the block before putting it on jack stands in the garage. Supposedly there were about 70 of these built and the front suspension was derived from the Formula Fords of the early 1980's. This is my first experience with a 7 and also with such unique components.

Upon inspection I discovered the car spent quite a few years as an SCCA roadracer. At some point in it's career, according to the info in the notebooks that came with the car, it clipped the haybales with the right front, notes then state "Installed wide suspension". The car was used for quite a few years after the suspension was modified, covering another 10k miles.

During inspection I found the left upper A-arm bushings were shot, allowing ~1/4" fore-aft movement at the UBJ. So I replaced all the bushings in the control arms with new and replaced the heim-joints and LBJ's as well.

During the initial reassembly, with no bolts tightened, I also discovered the left front Lower A-arm bolt hole is elongated allowing ~1/8" fore-aft movement at the LBJ.

I don't know how to weld so I'm pondering how to address the problem.

The LCA's are fixed length with no adjustments, that seems like a shortcoming.

So far, the "best" solution I've come up with is to get new LCA's built using heim joints at the frame. In this case since the 5/8" hole is "wallered out" I'll use a 3/4" ID on the front joint and retain the 5/8" ID on the rear. This way I can simply enlarge the holes for the front mounts and if I'm a little off it's not a big deal.

I'm open to suggestions...

Also... since the suspension was modified sometime in the 1990's I was curious about the geometry. I found Vsusp and measured everything best I could. After entering the info into Vsusp I found in some conditions (mostly ~2-3 roll angle with the suspension compressed and/or extended) the roll center would briefly shoot way outside the vehicle width. I have all of 30 minutes learning about suspension design, so I'd appreciate input on the current design. There are a couple of unnerving spikes in some of the graphs, like this one...

Link to my suspension Rotus-2.1

Thanks


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PostPosted: January 8, 2022, 9:37 am 
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Location: 4AGE in S.E. Michigan
Post your location. Some one here, my be close enough to help you weld the bracket. 2nd option most welding shops will have a mobile welding set up.
Davew


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PostPosted: January 8, 2022, 9:56 am 
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Congrats on your purchase! We’d all like to see more of it.

I expect the wide suspension was a kit with longer control arms and steering links with no modification to the locating points but your vsusp looks like the rotus could be improved or the data entered is not correct. I tweaked the chart with no change to your specs in order to see what we normally look at:

Rotus-2.1 chart update
Ride height adjusted to level the LCA, estimate of UBJ spaced an inch higher is much improved with twice the camber gain (if you set static camber the same) and about half as much RC migration:
Rotus-2.1 chart update, lvl lca, 1 inch spcr ubj

Spacing the UBJ should include fully welding of the spacer to the upright and a grade 8 fine bolt with as few threads as needed (longer unthreaded shank) or rebuild the fabbed upright. I also don’t see a safety washer on the UBJ to keep the UCA from popping off the ball in droop.

There is a lot of scrub due to the upright design and wheel offset. Not easy to fix with fab and welding and/or special high offset/backspace wheels that would likely hit the raised UBJ. Could also be data error.

Imho, ideally, the UCAP on the frame should be lower and further outboard but again, lots of fab and weld.
Regarding the slotted LCAP, all have some clearance when loose to allow for assembly and sometimes adjustment. That’s why alignment checks are always with the bolts tight. However, 0.125” is quite a lot.

If I could not weld or find someone to weld a 1/8 strip washer over the flange, a heavy washer under the head with an external tooth lock washer could be used:
https://www.mcmaster.com/standard-washe ... /id~0-656/
and
https://www.mcmaster.com/standard-washe ... ial~steel/

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 8, 2022, 11:40 am 
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Joined: November 6, 2020, 6:29 pm
Posts: 440
Location: Spring, TX
Interested to see more. I'm building a rotary 7, but am the 3rd owner of the project.

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http://www.locostusa.com/forums/viewtopic.php?f=35&t=20899


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PostPosted: January 8, 2022, 3:09 pm 
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Joined: April 23, 2006, 8:26 pm
Posts: 6281
Location: SoCal
I know the engineer that designed the Rotus suspension and highly doubt that he did it wrong, as he’s still very happy with it, specifically the front suspension. I agree that maybe there was some measurement error. If not, someone along the line likely changed the A-arms, the pick up points, or maybe even the uprights. Regardless, you have what you have and you have to make it work. If you're unhappy with it as-is, very carefully double check all the pivot point dimensions and start in on redesigning it. First try, I'd leave the inboard pickup points where they are, as well as using the existing uprights, and see if you can get it where you want. If not, start altering the A-arms as well, keeping mind that altering the length of the upper A-arm will change your shock ratio.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


Last edited by KB58 on January 8, 2022, 6:29 pm, edited 2 times in total.

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PostPosted: January 8, 2022, 5:28 pm 
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Along those same lines, you could try to validate some data by physically checking for camber gain with travel, scrub with a wheel off and suspension at ride height, with a rod or ruler through the ubj and lbj as viewed from the front and mark where it strikes the ground then mark were the tire center line would be and measure the distance between them.

Yes, we are not bad mouthing anybodies work, especially suspension which is full of compromise anyway.

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 8, 2022, 7:00 pm 
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Joined: January 7, 2022, 9:53 am
Posts: 45
Location: Buda, Tx
I appreciate all the feedback! I just wrote a lengthy reply but lost it because I guess I took too long and the site wanted me to log in again... doh!

-take 2: apologies for my rambling writing style, I draw pictures for a living for a reason...
The car was listed as having a 2.3L Ford Lima (Pinto) motor and a T5 transmission. I assumed it was a 'regular' motor with some hop up bits... nope, pretty much full on race motor, lots of Esslinger speed parts, dual DCO50 Webers, cam rated for 6-10K rpms... yikes! I also discovered the car spent at least 6 years as a race car...hmm.

My short term goal is to make sure the basics are functional and safe, then assess the motor/drivetrain as I have my doubts about the civility of the engine. Longer term is a fun, somewhat reliable car for sunday sprints thru the countryside and autocross/driving events. Perhaps a modern Ford duratech with ITB's and IRS.

Originally the Rotus used oem Toyota steering parts, this car replaced all but the steering rack and ITR's with 'bespoke' parts. The upright is next to nothing, I don't know if the original ball joint locations were carried over to the current design, that's why I wanted to find a software program. It's obvious I'll need more precise measurements to confirm. Although according to the notes the car covered more that 15k miles with the current parts so it's likely better that my numbers suggest.

Further disclosure, the last post was getting long so I left a few things out...

With the mention in the notes of hitting the hay bales I had my suspicions about the frame, though most of my measurements were within the plumb bob and tape measure fudge factor something wasn't jiving. When I was initially disassembling the front end the 5/8" x 10" UCAP bolt was difficult to remove, I had to use a wrench to unthread it thru the bulkhead and once it cleared the end of the bolt sprang up ~1/4"... further inspection found a bend sq. tube just above the pivot bolt mount, hiding beneath some bright red wires.

That same sq. tube is deformed slightly near the bulkhead also. Just now I checked the lower frame tubes from the bulkhead with a carpenters square and they appear to be bent to the left ~1/8" over a 12" span. Also the LCA's aren't parallel to the bulkhead, the gap from the rear tube to the bulkhead is ~1/2" consistent on the RH, the gap reduces quite a bit on the LH LCA. I also neglected to mention the wheelbase on the left is ~95-3/8" where it's ~95-13/16 on the right.

Since some fairly involved work is required to correct the issue, and I want to see what the motor is like, I decided to use the shade-tree method of correcting the mount tube... I bought a 5/8" drill bit and some cutting fluid and managed to remove enough material from the top-front and lower-rear of the tube to get the bolt aligned with the bulkhead hole.

With all this info swimming around in my head pondering how to get the wheels back where they should be is how I stumbled onto the adjustable LCA idea. If they aren't too expensive seems like it could make the bent frame issue not a big deal. I don't intend to change the geometry. I modeled the front end based on my measurements and came up with the adjustable LCA shown on the left side of the car with the existing on the right. It seams like a reasonable design, but I'm open to suggestions. There are a few racecar fab shops in the area, I'll try to talk to one next week

Miatav8,MstrASE,A&P,F - thank you for the feedback about the suspension layout, it's really interesting to see how large a change can come from such a minor change. I've read about suspension design a little, but it seemed too theoretical, having the graphics of Vsusp is really great.

KB58 - that's fascinating you know the guy! I have no doubts they had it right when the sold it, I'm was more curious to see how the current set up is. As for shock ratio, one of the notes indicates "original = 0.86, new = 1.19". It currently has the same 350#/in spring as the notes "Wheel Rates: new 247#/in, original 243#/in"

Fascinating stuff here


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PostPosted: January 9, 2022, 1:30 pm 
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Nice!

Concentrating on repairs, I suggest looking for a local “frame alignment” shop to repair the lcaps and left LCA which is also likely to be bent. They could have quickly corrected the UCAP misalignment as well with some heat and a rod through the boss. No need to cut everything out and they would be quick to get you back on the road.

The cooling fan may not have sufficient capacity (amp draw) for operating in city traffic. Hopeful there is a coolant overflow tank but I don’t see it.

Determine if it is solid lifter and check the wire thickness of the valve springs for an idea on the seat pressure. Check the compression too as the head may also have been excessively milled (check adjustable cam pulley setting). If the mods are too extensive, it may be better to swap the complete head for something more conservative to run pump gas and less rapid valve train wear with softer springs. You might just shelve the entire engine and exhaust for a used 90's lima and fit a dgv or holley 350 for now.

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 9, 2022, 2:34 pm 
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Posts: 45
Location: Buda, Tx
Thanks, it's quite an assembly of interesting parts! I hadn't really considered a frame shop, assuming they wouldn't be interested in something so 'unique', but I'll ask around.

The notes are quite extensive relative to the motor development and the owner was in direct contact with Doug Esslinger about different things over the years, one thing they discuss is the new triple valve springs good to 10k rpm. He weighed every component of the valvetrain, checked main bearing clearances frequently, shaved the head at least twice. It's definitely impressive, if you've ever seen a '70's Boss 302 head next to a standard 289 head, that's what this looks like compared to a Pinto head. The roller cam provides something like .63" lift... that's insane.

I'm hoping the PO didn't damage it, as he said he used 93oct pump gas

The top end looked good, valve clearances were almost right, no signs of damage. I put a small camera down the sparkplug holes and couldn't see and scoring, plugs looked rich...fingers crossed. I tried to do a compression test but my gauge wasn't holding the reading, but I could see they were all swinging to roughly the same region of the gauge while cranking the motor...cautiously optimistic.


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PostPosted: January 9, 2022, 7:27 pm 
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Since this seems to have been an all out effort, you may have the tall SVO block that can be bored and stroked out to about 3.0L.

I'd try just a cam swap or regrind without reducing the base circle, add a quiet exhaust back to the rear fender with a turn out, then retune the carbs. If needed, a head saver shim (.020") should drop the compression about 1/2 a point. Probably a walker quiet flow, long round muffler then weld tabs to fit a stainless shield around it or just have it ceramic coated.

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 10, 2022, 11:15 am 
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That's a very interesting cam profile. It reminds me of the old Isky 404 profile for flathead Fords, which was very radical in its day. It must have a very lumpy idle.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: January 10, 2022, 12:54 pm 
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Also, you may want to convert back to hydraulic lifters. They should have the same od.

You may not want to park this for a year converting to a different engine and sorting out the injection and fuel system changes.

I have an ancient Esslinger catalog. All the roller follower cams from esslinger were circle track cams back then. The mildest was 4500-7800rpm with 260@.050, 650 int/exh, 288 adv dur, 109.2 cl.

I think a good street/strip cam for this would be the 2200-6500rpm flat tappet/cast follower spec with 236/246@.050, 437/463 int/exh, 272/282 adv dur, 110 cl.

The factory roller in the 90s 2.3 is very mild but another option and could adapted to a dgv using the ranger lower intake. It is similar to the earlier 80s 2.3l lower but the ports are further apart.

The complete ranger engine would be a very easy swap if you didn't want to undo all the hard work that went into the current setup or had a buyer for it as-is. Tough decisions to make.

http://schneidercams.com/pinto4cylinder.aspx
http://www.rmcompetition.com/custom-gri ... afts-.html
https://www.bo-port.com/index.php?act=viewCat&catId=1
https://www.therangerstation.com/tech_l ... ders.shtml

Grind on a 90's ranger roller core or your own core:
https://deltacam.com/services/camshaft-grinding/

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 10, 2022, 9:22 pm 
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Posts: 45
Location: Buda, Tx
Good gravy, you're a wealth of knowledge!! I really appreciate the feedback/advise. I've had so much new info swimming in my head, your plans sounds like a good path to follow. I'm pretty sure it's a turbo 2.3 block, decked, align bored and who knows what else. I'm thinking new pistons might be needed to get down to ~10.5 or 11:1, that seems livable, maybe.

You're right about not wanting to park it, just yet at least. I like your plan of taming the motor a bit, I'd like to use this head if possible, but we'll see.

The cam is the 2232.5 , did someone say lumpy? :)

The front face of the cylinder head has a series of numbers stamped onto it, one day I'll call Esslinger and see if maybe they have records, and can maybe provide some specifics


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PostPosted: January 11, 2022, 2:43 pm 
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On the exhaust front, if the pipe after the header is 2 inch, this is the muffler I’d use to save the ear drums.

Walker SoundFX 18553, 2” in/out, 25x6 inch round case, and about $40. Checks all the boxes for quiet, overall length to run parallel to the frame with a mandrel bent turnout, and it is locost:
https://www.summitracing.com/parts/wlk-18553

If the pipe is 2.25, 17166, 2.25” in/out, 26x6.5 round, and about $30.
https://www.summitracing.com/parts/wlk-17166#overview

You’ll want to fab a heat shield from .050” 300 series stainless (don’t perforate) with an inch overhang on each end and weld four, 1x1x1/8 tabs to the muffler end cap edges 90 degrees apart to mount the shield.

Another alternative is to buy a caterham or westfield exhaust assembly to adapt. Probably the easiest and best looking option. They both have U.S. distributors for parts. The pipes will probably be 2 inch.

_________________
Miata UBJ: ES-2074R ('70s mazda pickup)
http://www.vsusp.com
ford IFS cheap viewtopic.php?f=5&t=13225&p=134742
Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
Tiger Avon: 114x40x13.3-12.6
Champion (Book): 114x42x11
Gibbs Haynes: 122x42x14
Voo Doo: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


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PostPosted: January 15, 2022, 10:54 am 
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Posts: 45
Location: Buda, Tx
There were/are no bump stops aside from the rod ends/spherical bearings as the mechanical stops for droop and the fully compressed shock is the other.

There was a crusty old 1/4" thick rubber one on the shock for compression. I replaced that with one ~3/4" thick, sold as a 'universal' shock mount bushing.

I've been looking for info on limit straps and don't find a lot here, Summit sells these https://www.summitracing.com/parts/tgi-111277-kit#overview but they have 1/2" mount holes where I have 5/8" bolts thru the top of my shocks... and I'm not sure where/how to attach them to the frame. Open to suggestions/ideas/pictures.

Happy Saturday!


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