LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently July 30, 2021, 9:29 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: February 20, 2020, 2:49 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
Ok, I hope I can explain this properly. I’m redoing the front suspension and brakes on my British made locost. While painting the lower “A” arms I noticed that they sit flat on a perfectly flat surface. They rock about 3/8”corner to corner. I thought this must be how they were made but they both rock the same and not a mirror image like you would expect if they were made to be that way. Should I take them to a place that has a good strong hydraulic press and have them straightened out so they lay down flat??? Or should I just put them back on as they are? They look to be made from pretty strong material. The upper “A” arms seem to lay flat. Russ

_________________
You meet the nicest people in a Locost Se7en.


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 2:52 pm 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 6988
You should improve them so they don't bent further or back and forth. They may work better with the bend so I would not necessarily bend them back. Any pics? Maybe we can figure out why they bent and what to do about it.

_________________
MV8

https://www.youtube.com/watch?v=Om3C1Ep ... D3E18BB447


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 2:57 pm 
Offline

Joined: October 3, 2009, 1:33 pm
Posts: 33
Location: FL
If you can achieve the correct alignment then it should be good. Bending the members will reduce the remaining ductility in them (slightly). The vehicle doesn't know if the suspension is bent or not, it will behave as the alignment directs it.

_________________
Thinking is the greatest leverage on effort
Great workmanship will not turn a bad idea into something good
Poor workmanship can ruin a great idea
R1 single seat track car, in progress
Maxima VQ35 mid-engine 2 seater track car, on hold


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 3:08 pm 
Offline

Joined: February 8, 2014, 10:47 pm
Posts: 738
Location: Cornholio OR "Where the magic happens"
Pictures would help, I don't understand how a triangle can be bent.
Any 3 points are always in the same plane.

Any bending would be from, for example, where the spring connects to the arm causing the area between there and the ball joint area to bend up. (we have seen this type of failure previously here)
Or the ball joint end be to bent back from braking forces, or from clipping something on a turn.

Bending them back would not be a good move, as they will just fail again.
Best to redesign the arm adding strength where needed to resist bending.
Or correct the design to prevent binding that caused the bend.

Since they are not mirror images perhaps they were built that way (unintentionally?)

I again ask for pictures as this may be a significant safety issue that should be addressed before the car is operated again.

_________________
I don't know who I am, when I am somebody else.


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 4:14 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
Ok I'll try to send some pics. This is what both "A" arms look like:


Attachments:
_IGP9973.JPG
_IGP9973.JPG [ 1.73 MiB | Viewed 5008 times ]

_________________
You meet the nicest people in a Locost Se7en.
Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 4:19 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
Balancing on the shock plate. If you look at the bushing end of them the left "A" arm it measures 1 3/4" to the top of the tube that holds the bushing on the left side of the pic and 1 13/16" to the top of the right side. On the right "A" arm it measures 1 3/4" to the top of the tube that holds the bushing on the left side of the pic and 1 7/8" to the top of the right side.


Attachments:
_IGP9974.JPG
_IGP9974.JPG [ 1.81 MiB | Viewed 5008 times ]

_________________
You meet the nicest people in a Locost Se7en.


Last edited by trialsmangasgas on February 20, 2020, 4:25 pm, edited 1 time in total.
Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 4:23 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
In this pic your looking from the wheel side of the "A" arm balanced on the tubes. The shock mount plate on the left "A" arm is tilted up .4 degrees up to the right. The shock mount plate on the right "A" arm is tilted up .2 degrees up to the right.


Attachments:
_IGP9975.JPG
_IGP9975.JPG [ 1.63 MiB | Viewed 5008 times ]

_________________
You meet the nicest people in a Locost Se7en.
Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 5:19 pm 
Offline

Joined: February 8, 2014, 10:47 pm
Posts: 738
Location: Cornholio OR "Where the magic happens"
It's hard to say from this distance, it appears to me to not be a bend but sloppy assembly? (poor jigging or welding technique?)

Being that the bars continue past the weight bearing point and connect fairly directly to the ball joint mounting area those arms seem to be strong enough.

My only concern is.
I would hope that the ball joint is inserted from the bottom through the hole in the arm plate and the car is not supported by (2) 5/16 bolts?

_________________
I don't know who I am, when I am somebody else.


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 5:22 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
I may have just answered my own question. If the bushing tubes are level and aligned (which they appear to be) then it should not matter if the plate holding the BJ and lower shock is off a degree or two the BJ and rubber in the lower shock should be able to overcome that minor difference. Russ

_________________
You meet the nicest people in a Locost Se7en.


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 5:35 pm 
Offline

Joined: February 8, 2014, 10:47 pm
Posts: 738
Location: Cornholio OR "Where the magic happens"
Yep, in the end they are just a bridge between the frame and the upright and they are not showing signs of bending or cracking.

And that the ball joints are installed from below the arm, I see no reason to not run them as is.

_________________
I don't know who I am, when I am somebody else.


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 5:49 pm 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6145
Location: SoCal
Bent Wrench wrote:
...it appears to me to not be a bend but sloppy assembly? (poor jigging or welding technique?)...

Agree, and also agree that it doesn't matter (assuming that you aren't leaving out something like "well there was this huge pothole one day...", and that the shocks have never bottomed out, and that the A-arm can't, under any circumstances, hit the frame, etc...).

Actually, looking at the on-edge picture again, I see why it's that way... the plate was welded in slightly crooked, with the right side being slightly lower than the left. As was said, it doesn't matter, though *I* would add a stiffener bar under the shock bracket. As it is, it seems like an eventual metal fatigue failure could occur due to flex.

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


Last edited by KB58 on February 21, 2020, 1:17 am, edited 1 time in total.

Top
 Profile  
Reply with quote  
PostPosted: February 20, 2020, 7:14 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
Thanks guys

_________________
You meet the nicest people in a Locost Se7en.


Top
 Profile  
Reply with quote  
PostPosted: February 21, 2020, 5:50 pm 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 6988
For the inevitable pot hole on the way to the big show, I'd reinforce with vertical, 1/2 inch strip near the coilover flanges. Is that powder coat?

_________________
MV8

https://www.youtube.com/watch?v=Om3C1Ep ... D3E18BB447


Top
 Profile  
Reply with quote  
PostPosted: February 21, 2020, 7:25 pm 
Offline
User avatar

Joined: March 3, 2006, 10:48 pm
Posts: 1524
Location: Shawnee, Ks
rattle can

_________________
You meet the nicest people in a Locost Se7en.


Top
 Profile  
Reply with quote  
PostPosted: February 23, 2020, 9:15 am 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 6988
If you want to improve these at some point, here is one way that should minimize the amount of fab or you could just add the light blue flange.
Make a wood jig of the old dims.
Reuse the lbj plate but trimmed along the red line, new tube for pivots to save effort and same od tube for the legs.
Slot the legs so the lbj plate fits into the center of the tube.
Add the light blue 1x1/8 flange.


Attachments:
trailsmangaggas lca.JPG
trailsmangaggas lca.JPG [ 120.13 KiB | Viewed 4798 times ]

_________________
MV8

https://www.youtube.com/watch?v=Om3C1Ep ... D3E18BB447
Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 14 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY