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PostPosted: December 27, 2015, 8:49 am 
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I understand

Here is my final tweak (not to change your final. I just like tweaking):

MV8 Final

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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


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PostPosted: December 27, 2015, 6:40 pm 
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Miatav8,MstrASE,A&P,F wrote:
I understand

Here is my final tweak (not to change your final. I just like tweaking):

MV8 Final


I totally understand that. This link is actually a pretty good one actually and exactly the same lower mount as the first design. I'll keep on looking if you keep changing 'em. That's the nice thing about digital drawing boards these days.

I was experimenting with an UCA today that is the pivot for an inboard mounted shock. The shock is mounted at a 5 degree angle at ride height and is near 0 degrees at 3inches of bump. The UCA it's self provides a .72 motion ratio (8.63/11.98) but, beyond that I've got no idea of the math needed there.


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PostPosted: December 27, 2015, 8:28 pm 
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I don't follow. My lower what is exactly the same as which one? I looked through the designs again and saw nothing identical.

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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


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PostPosted: December 27, 2015, 10:36 pm 
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Miatav8,MstrASE,A&P,F wrote:
I don't follow. My lower what is exactly the same as which one? I looked through the designs again and saw nothing identical.



The LCA pivot in your last link is 3.2in above the frame, and that's the same height but, it's further out then my orignal, that's what I meant, sorry.


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PostPosted: December 28, 2015, 8:42 am 
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Nema problema. I just didn’t know what you were talking about is all.

I'm not sure exactly what the question is. What are you trying to determine? The required motion ratio to be provided by the uca rocker ratio and spring rate are usually results, determined by the sprung weight plus occupants, coilover travel and desired wheel rate.

Which books are you using?

Also, there are considerations for geometry and switching spring loaded arms.

All I know is your vsusp 58middy and the front suspension is miata based.

_________________
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


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PostPosted: December 29, 2015, 6:56 am 
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Posts: 110
This was kind of the idea I was going for.


Attachment:
Capture2.PNG


It's rough measurements. I didn't really play with the suspension much but, this is what it looks like at it's current numbers.

Middy 58in

I wasn't sure how to calculate the actual motion ratio here because of the angle of force from the spindle, the angle of the actual upper arm, and the angle the shock is mounted at. With this configuration at 3in of bump the shock is nearly vertical.

Seems like a bunch of force on the upper ball joint though between the spring and turning and such. If I mess with a bellcrank any I may just stick with other geometry and the LCA attachment...

As far as books I've got Herb Adams - Chassis Engineering, Des Hammi - Kit Car Suspsension (I abrev. title name) and the Midlana book.


You do not have the required permissions to view the files attached to this post.


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PostPosted: December 29, 2015, 6:33 pm 
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Damper angle is relative to a line drawn between the ucap and the damper upper attachment center; 90 degrees at full bump and ideally no less than 80 degrees at full droop. The motion ratio is a separate determination.

The math is the law of cosines, which you can rearrange to find for the adjacent sides or just keep plugging in numbers to zero in on the correct inner uca length. Using VSUSP, check the ucap outboard angle at zero bump then subtract that from the angle at 3 inches of bump. This gives you the angle to get the cosine from.

EDIT: I screwed this up so I am fixing it now (below).

If you want a motion ratio of .72, for the wheel rate, use spring stiffness required at the wheel for the sprung weight. I'll assume about 1500# total wt so 1/4 of that minus unsprung, maybe 80# for a corner wt of 1500/4-80= 295#.

295 / motion ratio squared for 295/0.5184 = 570# spring effective rate when compressed to ride height, depending on how much droop you have available. With 3 inches of droop, that's 2.16 inches of damper travel for a 136# spring.
With 2 inches of droop, a 205# spring would do. I still think a 150# is close to what you want if you have 3 inches of droop.


Also, the ubj will be under compression rather than tension for a lbj. I'd use the oem ubj or tie rod and regularly check for wear. If it does wear too quickly for your taste, ream the spindle for a heavier duty joint.

_________________
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


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PostPosted: January 1, 2016, 5:14 pm 
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Posts: 12
Location: Chicago Ill
Hi fellas, I was looking for some advise on this set-up, Im not really sure what Im doing right or wrong. I am open to any build from scratch for a 46" track width set-up using na miata knuckles, I'm just about ready to start on the front of my build so any info would be awesome.

Thanks, Scott.

default values


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PostPosted: January 1, 2016, 7:48 pm 
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Looks like a track only ride at 2 inch gc.

The front track should be as wide if not wider than the rear, whatever the rear is going to be.

The tires are massive for what I assume is a 1500 lb or less car, so if it is a short track, you may have difficulty keeping street tires hot enough to work well. Consider a 205.

Static camber is what people add when the suspension isn't getting it done. No need to add static to the design phase, as it just makes the numbers look better than they are.

The rack will probably need to be about 18-19 inches between the inner pivots.

There is a lot of scrub, which should be minimal if any. If you created the scrub in trying to reach the track width desired, use frame width or arm lengths instead.

Need more info about the build specs and purpose of the car.

_________________
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


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PostPosted: January 1, 2016, 8:07 pm 
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I just found your build page. It helps to put a link to your build in your signature block that displays every time you post.

Based on this new info, I assumed the offset was wrong and changed it to 2.2 from 1.0 to reduce scrub.
To adjust out the camber, I lengthened the uca to 7.11, which is 0.625 of the lca length.
These changes narrowed the track, so I widened the frame which will allow a slightly shortened miata rack to be used at around 21 inches, maybe.

default values

The results are no loss of camber in roll, no static camber to wear the tires out, fairly flat and reasonable rc height at 3 inches, and a swing arm greater than 32 inches at 5 degrees roll.

If you want to use an unmodified miata rack of 24.5 inches, I can work on that.

_________________
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


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PostPosted: January 1, 2016, 8:20 pm 
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Joined: January 1, 2014, 8:13 am
Posts: 12
Location: Chicago Ill
Thanks for posting the info! I see you found my frankenstein build so... A little more info of the build.

The rear is done and all tied together with a 48" track width with a 9" wheel with a 1" offset, square set-up all around. I thought I would have the same width in the front but I dont due to fender clearance resulting in a smaller track width, stupid mistake. What's the result of this set-up?

Thanks again, Scott.


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PostPosted: January 1, 2016, 8:31 pm 
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The link in my post "default values" is the default name for a link to every combination of settings.
That particular one is yours. Just change the wheel offset back to 1 inch and subtract 0.6 from the frame upper and lower to the center to bring it back to 46 inches.

_________________
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


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PostPosted: January 2, 2016, 6:31 am 
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Miatav8,MstrASE,A&P,F wrote:
The results are no loss of camber in roll,


I make mistakes too. Not sure where I got zero camber loss from; obviously not! I made the changes and posted that in about a minute. Camber gain is the same as yours without the static at .5/degree.

Using the graph, the lower/flatter the camber curves are in roll, the more gain there is in roll to combat the loss.

Putting the camber peaks on top of the rc height seems to work well.

The rc should be flat through the range of roll allowed by the spring rate and swaybar.

The instant center swing arm pivot (pink dot) should not cross the rc (green dot) at the maximum allowed roll angle.

This one was tweaked for a wider rack; it will have the same camber gain with half as much static, lower rc, and sa longer than 30 inches at 5 deg roll.
default values

_________________
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


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PostPosted: January 2, 2016, 7:45 am 
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Joined: January 1, 2014, 8:13 am
Posts: 12
Location: Chicago Ill
Thanks for this. I think im starting to grasp vsusp with the way you explain things, appreciate your time.

Scott.


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