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Req Droop% 100 Frequency 83.99 CPM Extended Compressed Travel Rideheight
1.40 Hz 9 7 2 7.0
Corner sprung wt req travel (Control) 10 7.5 2.5 7.5
250 5 50 Req wheel rate 11 8 3 8.0
droop 5.00 12 8.5 3.5 8.5
bump 0.00 13 9 4 9.0
14 9.5 4.5 9.5
wheel to pivot shock to pivot Arm Installed MR 15 10 5 10.0
16 D2 7.00 D1 0.44 16 10.5 5.5 10.5
17 11 6 11.0
18 11.5 6.5 11.5
Spring correction 261 For Arm Motion Ratio 19 12 7 12.0
20 12.5 7.5 12.5

Spring corrected for tilt and motion ratio
261 272 281 297 319 348 396 443 522
Tilt Deg (A) 0 10 15 20 25 30 35 40 45
Total MR 0.44 0.43 0.42 0.41 0.40 0.38 0.36 0.34 0.31


shock travel req. 2.2 2.1 2.1 2.1 2.0 1.9 1.8 1.7 1.5

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Thom

meant to say LCA.

Thom

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Thom

So you have close to my rates in the front, I have 425. I also am running 42 degree shock angle. I did weigh the car with me I it and full fuel. The one I got bit on is the rear. Started out at 300 and ended up at 425 with 2 people in the car, full fuel with 20 degree shock angle. It took up rating the rear to stop hitting the bump stops. My front corner weights came in around 375. I have some reservations about the calcs as opposed to the real world. Order the springs from some place you can exchange them from because it doubt your going to be happy the first time around. Just my experience anyway.

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Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

Many of your inputs don’t look right to me. Before calculating, you need to perform a mock up of the coilover to determine the motion ratio, mounting angle, droop, and necessary coilover travel. I don’t think you will be able to use the existing upper coilover mount. Mock up a “coilover” with threaded rod and 2.75 inch rigid washers (plastic, wood, foam, etc), then lower the LCA to where you want full droop. Put the lower pivot eye as close as practical to the LBJ, then tilt the upper pivot eye outboard as far as necessary to clear the UCA.

Have you completed anymore work on the LCAP framing? Last pic I saw was a year ago.

With 2 inches of droop, the rate at the LBJ should be about 0.65 x the corner weight for sport touring (i.e. semi-casual with cup holders). The actual spring rate will be higher due to motion ratio of the LCA and coilover mounting angle, since coilover compression is less than wheel travel.

Hypothetical: If the LCA ratio is 14/12 (0.86) and the coilover angle is 20 deg (0.94), if the corner weight is 325 then:

325 x 0.65 = 211.65 / 0.86 = 246.1 / 0.94 = 261 lb spring rate. At full droop, the spring will come off the seat less than a 1/2 inch. Should never be a problem unless you have a habit of jumping things (Thom, the estranged, red-headed step-child of the Duke family?).

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

The front suspension is complete. The figures in I posted are the dimensions as it is set up It is a Mustang II design. Tubular upper and lowers. The shock mounts are just tack welded. I did set up a mock shock yesterday.



I plan on replacing the uppers with adjustable capabilities. It will help with alignment in the future.

https://www.ebay.com/itm/Specialty-Prod ... 1683186127

Thom

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Thom

You need a bump value in there too. You’ll never have 100% droop. Also run a 20% stiffer rear if you can so you set up some sort of flat ride quality with the frequency. I tried, it didn’t really work out. I set the rebound differently from front to back so it don’t get a tether-totter going.

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Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

I was referring to a bad ‘80s tv show with an orange mopar.

The upper spring seat looks like it will be really close to hitting the UCA cross shaft at full droop. Consider stock NA miata springs are around 150/100# f/r but more efficiently installed and made soft enough to satisfy everybody.

Brunton is going by the tire centerline leverage where most calc based on the LBJ which is partly why the MR looks so bad. I'd rather do my own math than rely on a spreadsheet that I can't modify.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

When I used the formula above- I get 308lbs. That's very close to Burton's calc of 319lbs. I can move the upper Shock mount out. Right now I have a little over an inch clearance. And for the rears it came out 127.8lbs.

Nick47 used 350/140lbs. He felt it was too stiff and was going to switch to 300/120lbs on his MGB powered car.

So I think going with 300lbs frt/120lbs rr may be the way to go for a street car- not track use.

I need to get the coil overs so I can do a final position for the upper mount. The little difference in shock angle will not make a lot of difference in the required spring rate.

Thom

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Thom

I just went thru the QA1 Tech calc table for spring rates. Using their calc I should have 240lb front springs and 105lbs for the rear. Since a Cobra replica uses 345lbs for a 625lb wheel load weight (2500lbs) on the front vs. 300lbs (1400lbs), I think something along the lines of 250lbs makes sense. But I think 105lbs for the rear seems light. I think 120lbs makes sense from what everyone else has in a live axle.

Thom

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Thom

Did you add all your weight for 2 people and full fuel? That was one mistake I made. As light as my daughter is she made a big difference in how the rear end reacted on bumps. My bump experience want bump either, it’s compression. Keeping it from hitting bump stops was the challenge at speed. At 70 going through troughs on the road really compress the springs.

_________________
Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

It makes a difference in how heavy the damping needs to be and lower rate springs are thinner and lighter. You could at the same time move the lower coilover pivot toward the LBJ about 2 inches without the uca hitting the spring in droop. That would make a bigger difference in the necessary rate. You might also want to raise the upper and or lower the lower to fit a coilover where the spring doesn't stack solid at full comp length and still has some adjustment either way from ride height. Might look at smaller than typical spring ODs to maximize the fit if they still clear the coilover body.

Here are some ideas for moving the lower pivot closer to the LBJ and lower.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

[/quote]It makes a difference in how heavy the damping needs to be and lower rate springs are thinner and lighter. You could at the same time move the lower coilover pivot toward the LBJ about 2 inches without the uca hitting the spring in droop. That would make a bigger difference in the necessary rate. You might also want to raise the upper and or lower the lower to fit a coilover where the spring doesn't stack solid at full comp length and still has some adjustment either way from ride height. Might look at smaller than typical spring ODs to maximize the fit if they still clear the coilover body.

Here are some ideas for moving the lower pivot closer to the LBJ and lower.[/quote]

So I looked at your suggestions MV8 and I agree. But the more I review what I designed, the less I like it. It is more "hot rod" in looks than Lotus 7.

So I have decided to redesign the UCAs. I have the upper ball joint collar rings. I used (for mock up only) my swedged tubes from the rear (will purchase the final correct lengths). This corrects the look, and gives me more adjustment for alignment.



I worked with the V Susp program to get my numbers right. The four bar rod ends will be replaced with ball rod ends on all of the frame pivots allowing for less movement resistance.

I will remove the angle iron I installed across the frame that supported the Mustang II UCA, and relocate the upper shock mount to the frame tubes. It will then be a little higher and allow a longer coil over shock between the higher upper mount and the outward placement of the lower shock mount. I will look at moving the lower shock mount closer to the LBJ, most likely use a top plate with a shock mount on top. There will be no problems with shock/spring fitment and add better control of the arm movements.

Thom

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Thom

The LCA anchor point will destroy that arm. You need to weld in a plate as close to the LBJ as you can. Then run that shock to the frame point you originally had. I read a bunch of text in the earlier posts about full deflection and how this front will operate. You will never, ever see full deflection. You’ll see about 2” up and 2” down in the life of your travel. I’ve set my bump stop and tracked its movement in the front and it’s way less than people think. You’ll drive your self nuts chasing this design.

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Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782

Thanks for the reminder to not get into the weeds Steve. I just could not live with the old design esthetically. It just did not fit the car in my head! I ordered the swedged tubes and heim ends. Should be here Wednesday.

Thom

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Thom

I have the new Vsusp set before I weld.


My new (longer) swaged tubes and QA1 Rod Ends arrive tomorrow. So I do a final positioning of the UCAs.
Old layout


This is the layout of the new UCA with the old UCA attach points removed. It is a much cleaner design and more adjustability.


I will fab new upper shock mount brackets once the UCAs are positioned.

I also have to get a reamer tool for the Tie Rod end so I an flip it over And I need to add the inner tie rod extender to get rid of the bump steer geometry.

But I am getting loser to the frame set up being done!

Any suggestions are welcome!

Thom

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Thom