LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently March 18, 2023, 9:32 am

All times are UTC - 5 hours [ DST ]




Post new topic This topic is locked, you cannot edit posts or make further replies.  [ 108 posts ]  Go to page 1, 2, 3, 4, 5 ... 8  Next
Author Message
PostPosted: September 2, 2008, 2:41 pm 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6317
Location: SoCal
[was: "My brother and his Stalker won the lottery, they're intact" -editor]

My brother's Super Stalker's been done for a while now and he's been taking it on various drives to get used to it. Many of the drives involve heading up into the local mountains to drive on twisty roads, early in the morning before anyone's out. This Saturday he was coming to a blind righthand turn at about 30mph and starts his turn in - no steering!

He managed to get the car stopped before it headed over a huge cliff on the other side, but which left him stopped in the middle of the on-coming traffic lane - on a blind curve. Because it was early morning, what could have be a very different story wasn't a big deal.

After he's stopped he tried letting it coast and turned the wheel again, and it turned like nothing was wrong. He gets it safely off the road, gets out and has a serious look to see WTF just tried to kill him.

As you may know, Brunton, the manufacturer, speeds up the steering by cutting the steering arms short and adds a part for the steering tie-rod to connect to. Picture a traditional rod-end with its swivel ball; now picture instead of the ball it's a one-piece part, no ball, and the hole is tapered. The part is screwed into a threaded hole drilled through the shortened steering arm, and the steering tie-rod end slips into the tapered hole.

The thread on thier fabricated part is massive, maybe 5/8" diameter, and right where the thread stops is where it failed, breaking clean off. The reason why the car acted like nothing was wrong when he turned the second time is because the castor on the non-steered wheel made it track the wheel that was still steering. The reason it failed on corner entry is because he had the brakes on, which pulled the left wheel outward.

My brother's learned that FOUR other cars have had the same failure. I looked at the pictures (I'll post them tonight) and asked him if the steering tie-rod that slips into it could have bottomed out and applied a sideways force. He said no, that it has plently of over-travel. I then asked how tight he'd tighened it. Due to how the part is designed, the body itself bottoms on the cast iron suspension arm, placing their adaptor not only in tension, but bending due to how the hole is never at exactly 90 deg to the arm (which is curved.) In otherwords, one side of the adaptor bottoms before the other, placing a huge bending force in addition to being under tension, in effect, saying, "tear here."

I'm posting this in case anyone has a Stalker or is contemplating modifying an upright to do what they did. On possible solution is to countersink the hole slighly so that the body doens't contact the steering arm, but it's not a great situation.

[edit: He says that Brunton changed the steering design since he bought his kit. Don't know what they did but it sounds like they became aware of "issues."]

Image
Image
Image
Image
Image

_________________
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 Anonymous on September 3, 2008, 2:46 pm, edited 7 times in total.

Top
 Profile  
 
 Post subject:
PostPosted: September 2, 2008, 2:44 pm 
Offline
Always Moore!
User avatar

Joined: November 9, 2007, 3:40 pm
Posts: 4075
Location: Pittsburgh, PA
Glad to hear it turned out alright. Theres something to be said for shaking down new cars in lower traffic areas.

Not that it really matters here, but I've always though the Stalker mod was on the scary side.

_________________
-Andrew
Build Log
Youtube


Top
 Profile  
 
 Post subject:
PostPosted: September 2, 2008, 2:46 pm 
Offline

Joined: December 17, 2007, 1:17 pm
Posts: 558
Yikes! Glad to hear he is just fine.

That right there is why I can imagine it would be so difficult to make a business of selling kits. The liability for such an incident has the potential to be HUGE.

Hopefully we all learn a bit more, and improve the breed!


Top
 Profile  
 
 Post subject:
PostPosted: September 2, 2008, 10:06 pm 
Offline

Joined: February 9, 2008, 1:05 am
Posts: 678
Location: San Antonio
Well, that's a mildly alarming story. Solidifies my decision to pony up for a proper fuel cell and steering rack eventually.

_________________
JSullivan


Top
 Profile  
 
 Post subject:
PostPosted: September 2, 2008, 10:54 pm 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6317
Location: SoCal
Posted pics... for some reason imbedding the image links didn't work.

_________________
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/


Top
 Profile  
 
 Post subject:
PostPosted: September 2, 2008, 11:59 pm 
Offline

Joined: August 15, 2005, 10:13 pm
Posts: 7043
Location: Charleston, WV
Wow. Looks like a nightmare. I hope they make good on it by giving him the "updated" parts. It's amazing to me that anyone would expect that skinny little bolt to be as strong as that beefy cast steering arm. I mean it is like 1/20th as thick. :?
Image

_________________
He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 12:29 am 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6317
Location: SoCal
The scale of the picture makes it look that way, but it's around 1/2-5/8" diameter.

_________________
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/


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 12:42 am 
Offline
Man of Constant Hazard
User avatar

Joined: February 20, 2006, 11:18 am
Posts: 3185
Location: Lexington, KY
I'm having trouble picturing what it is. Would you mind posting a photo of the entire upright as well?

JSullivan - Nothing wrong with what you're planning, but understand that Kurt is warning us about modifying the steering arm on the upright. Don't overlook that area...my amateur mind sees that as a much greater threat than the steering rack and fuel tank.

-dave

_________________
...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 1:17 am 
Offline

Joined: February 9, 2008, 1:05 am
Posts: 678
Location: San Antonio
dhempy wrote:
JSullivan - Nothing wrong with what you're planning, but understand that Kurt is warning us about modifying the steering arm on the upright. Don't overlook that area...my amateur mind sees that as a much greater threat than the steering rack and fuel tank.
-dave


Yeah, I wasn't too clear that I understood that, was I?

What I meant was that once I figure out the relevant dimensions, I'll buy something that works for those dimensions. I'd rather not risk my steering with poor fabrication or hasty planning! And minimize the amount of parts. Simplicity==reliability and safety in my mind.

_________________
JSullivan


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 8:37 am 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7654
Location: Massachusetts
So I think it's obvious from this, but just to be clear... The suspension needs to examined for freedom of movement thru it's entire range plus a little bit extra. You need to measure the shocks, extended and compressed and then cycle the suspension up and down with the shock removed and see what limits it's travel.

With a kit you assume that that was done for you, bit even things like changing the rubber bump stops could effect this. Clearly not all Stalkers were effected by this, considering the track footage I've seen. Ouch...

What a nightmare! So glad things came out ok....

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 11:18 am 
Offline
Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6317
Location: SoCal
dhempy wrote:
I'm having trouble picturing what it is. Would you mind posting a photo of the entire upright as well?


The best picture's probably this one. The green thing is the steering tie-rod. Its taper pin extends through the yellow block below it. That block brock off from the threaded rod you see sticking through the shoulder on the right. That's the cut-off steering arm on the upright. Brunton cuts it off, drills that hole through it, threads it, and screws that yellow block into it.

IMHO, the failure is caused by it bottoming unevenly in the threaded hole, applying both tension and bending loads.


Image
Image

Why can't I post pictures... I know how to do it and you can see the tags above...

_________________
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/


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 11:49 am 
Offline
Hack
User avatar

Joined: September 11, 2007, 12:23 pm
Posts: 621
Location: Marietta, GA
Ok, I understand now.

I'm assuming that part isn't heat treated. It seems like a design failure on multiple fronts.

The scary thing about these sorts of things is that it probably won't be detected with a visual inspection. Fatigue failure sneaks up on you.

Glad to hear they've addressed the issue.

_________________
William Conway
Building the Spartan 7 - Build Blog
LocostUSA Build Log
How do you eat an elephant? One bite at a time...


Top
 Profile  
 
 Post subject:
PostPosted: September 3, 2008, 3:04 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7654
Location: Massachusetts
KB58:
Quote:
IMHO, the failure is caused by it bottoming unevenly in the threaded hole, applying both tension and bending loads.


That's interesting. Sorry if I jumped to a conclusion. Was there a lock nut on the back of that part? Did bottoming of the suspension when the wheel was turned tighten it more? I would have thought it would have just cut the thread a little further...

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
 
 Post subject:
PostPosted: September 7, 2008, 6:46 am 
Offline

Joined: December 18, 2007, 7:10 am
Posts: 7
Location: Adelaide Australia
That setup wouldn't get past the first Engineering inspection, let alone the Rego inspection in Australia. A manufacturer allowing that sort of thing on the road is leaving themselves wide open to litigation when it fails.
The thread has no support and has failed at the root, it's obviously under severe load. I suspect the steering arm is "shortened" to speed up the steering response but that's a VERY agricultural and unsafe modification. That sort of thing is why we have Engineering requirements to adhere to in Australia.
Regards,
Mike.

_________________
Mike.
The "CLUBHOUSE"
Clubman Workshop.


Top
 Profile  
 
 Post subject:
PostPosted: September 7, 2008, 9:24 am 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 7754
There is so much wrong with this, I don't know where to begin.


A fix for the existing spindle is to use a rod end instead of the tierod end, a u bracket (such as one from Speedway) that fits tightly against the spindle over a larger area, bolted on with a separate, rolled thread, heat treated bolt and nut, then brazed along one side. Brazing is at a much lower temp than welding and very strong.

_________________
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
VoDou: 113x44x14
McSorley “442”122x46x14
Collins “241” 127x46x12


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic This topic is locked, you cannot edit posts or make further replies.  [ 108 posts ]  Go to page 1, 2, 3, 4, 5 ... 8  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 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

Jump to:  
POWERED_BY