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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 27, 2010, 11:20 pm 
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Location: Charleston, WV
STARMAN1 wrote:
has anyone thought of the bearing surface on those suspension brackets, since youe were talking about brackets???? i was wondering how long it would be before the holes elongated or the bolts failed???? I was also wondering if anyone ever checked those suspension bolts or the elongated holes after a few years of driving down the road with your loved one in the other seat beside you???? Any production car has substansial bushings and bobust brackets with oversized bolts going thru them. These are very important areas of concern.......................


The holes in the brackets shouldn't fail or elongate since the bolt going through the hole doesn't move or pivot but rather clamps things into place. All movement should take place about the rod end/spherical bearing or bushing that is being clamped by the bolt.

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PostPosted: September 28, 2010, 11:17 am 
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STARMAN1 wrote:
has anyone thought of the bearing surface on those suspension brackets, since youe were talking about brackets???? i was wondering how long it would be before the holes elongated or the bolts failed???? I was also wondering if anyone ever checked those suspension bolts or the elongated holes after a few years of driving down the road with your loved one in the other seat beside you???? Any production car has substansial bushings and bobust brackets with oversized bolts going thru them. These are very important areas of concern.......................


As long as you do not use thin sheet, they should be fine. I ran the numbers before building my car and 8AN bolts in double shear mild steel 1/8" brackets will typically be fine with a nice safety factor for the loads experienced by the typical 7 configuration. The numbers said they would experience a bearing failure at about the point the el-cheapo 2 piece rod-end connecting everything was rated to fail (although this failure mode seems to be unpublished). On the other hand, the 8AN bolt holding everything together would still be spotless in like-new condition since its ultimate strength is only three times as much as everything else. ;)

The hole failing in bearing is not the end of the world - in the aircraft industry its actually the design norm for riveted structure since an elongated/deformed hole will still be capable of carrying load. What you do not want in any structure is a tear-out or tension failure where the fastener tears through the end of the bracket or the bracket rips in two pieces. Life gets much worse when this happens since it has no load carrying capacity.

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PostPosted: February 11, 2017, 4:40 pm 
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My suspension brackets are made from 1/8" mild steel. Every 10,000 miles I dis-assembly the rod end and seals-its on each joints and clean and re-lube. I'm now over 40,000 miles and no sign of any elongation on any of the brackets. With 1/8" thick stock on a Seven you should not have any structural problems. Typical automotive suspension brackets are only about .150" thick, and last the life of the vehicle. The suspension loads should theoretically be fed into the sides of your typical "U" shaped bracket via the attachment clamp load, and not through the connect area between the bolt and the bracket hole. As Andrew already stated, we are way over designed for shear loads, we need the larger bolt size for clamp load. Dave W


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PostPosted: May 2, 2019, 4:24 am 
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Only 10 years late to the party. Since I have my CAD model, for complex intersections I start with a tube that is the correct length to it's longest tips, but i cut both ends square. Then while looking at the CAD model I scribe what I can with my caliper from the square end. Then finish up with a machinist protractor. Then I use an angle grinder with a thin abrasive wheel. Usually fits the first time.

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PostPosted: May 5, 2019, 2:07 pm 
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Joined: April 10, 2019, 2:33 pm
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Location: Northern Nevada
Been lurking here for awhile, but figured I could chime in on a subject posted earlier concerning the attaching hardware for control arms, etc. I have developed a project over the years involving a complete crossmember installation into a 60's era sports car that eliminated horrible geometry and outdated parts. Gave a huge improvement in safety as well as reliability and offered adjustability. The control arms were fabricated in jig assy's and tig welded. The attachment of the lower control arms were using poly bushings with steel sleeve inside the control arms along with an Oilite hat bushing in the crossmember that the 5/8" Grade 8 hardware with teflon locknut passed through. I thought the .125" material thickness of the crossmember might wear over time, so I incorporated a removable bronze bushing that could be easily replaced, thereby preventing the fabricated structure from elongation. This also allowed the 5/8" bolt shaft to ride on 1" of overall bearing surface instead of two 1/8" knife edges. I recently had this sports car apart last year and the control arms were stripped and inspected to look at the last 12 years of use and to my surprise, showed no wear of the components (Car weighs about 2300 lbs with 450HP and has been subjected to some autocross usage). I worked with aircraft flight controls over the years and incorporated a few ideas into my suspension design back in the mid 2000's when this particular project began. Just an idea for someone who might be at the crossroads into their build of a Locost and are at that point to make a decision. I recently acquired a built Locost chassis and thought I might like to incorporate the idea into the suspension. I would like to change the control arm design to something like mine that offers the adjustability. And as I looked at the chassis here, I thought I'd like to move the motor back, maybe a different roll bar design, radiator and steering rack placement, etc, etc..... Just food for thought.


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