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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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Location: Fort Worth, TX
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the point the el-cheapo 2 piece rod-end connecting everything was rated to fail (although this failure mode seems to be unpublished).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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Joined: September 22, 2005, 8:12 am
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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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