Re: Trailing Arm Bolts - Engineering

[tobyp@xxxx]

Hello List - 

I guess that I had better start with an apology to all of you. I had 
wanted to make my ealier comments "value added" to the DeLorean 
community, but I obviously missed the mark. I am sorry for diving 
head first into the pool without asking you if you wanted to go for a 
swim. With that said, I will offer my conclusions on my studies of 
the TAB situation, without a lot of lecturing on my part. All of the 
following are "in my humble opinion", and I invite discussion on any 
or all of it.

The key issue in the trailing arm installation is that the TAB's are 
bending under the loads applied while driving. I don't believe that 
the issue is that the nuts are backing off, and allowing the joint to 
become loose. The numbers suggest that the bolts are stretching and 
relaxing due to tensile yielding, because the numbers for that are 
somewhat lower than compressive yielding. The bolts are getting 
stretched slightly everytime they are loaded up to the point of 
bending, and the little stretches, over time, will cause the bolt to 
get slightly longer (This is actually called 'creep'). This causes 
the bolt/nut to appear to come loose. As the bolt stretches, the 
other components in the joint (washers, sleeves, etc) begin to move 
around as the bolt bends, resulting in wear at each point where the 
parts are pressed together. This actually adds to the loosening of 
the joint. All of you have either seen or heard of the wear and 
fretting on the washers, etc. I better stop this ... I'm beginning 
to "go there again".

Bottom line - Yes, I have used science and engineering principles to 
design a bolt that will not bend or yield, at all, under the loads 
that I believe that we are seeing in this critical joint. I have 
installed them first in my car, and then in several others. I am 
absolutely convinced that I will never have any joint loosening or 
any more wear of any of the noted components in these cars. I will 
never have to think about bolt rust or corrosion again. I talked at 
length with the manufacturer, and he is willing to forego profit for 
these custom bolts. He just needs to cover his costs of making them, 
so that the accounting department doesn't have a fit. However, this 
level of quality is not cheap. If you want the best, you have to pay 
for it. But, you only pay once. For a moderate-sized batch of bolts 
(200 pieces), with very good aerospace-quality NAS1805-7 self-locking 
nuts and hardened washers (for grip length adjusment when 2 or less 
alignment shims are installed), and including repacking and shipping 
to you, it's going to cost about $66 per car (2 bolts, 2 nuts, and 6 
washers). I am talking with Darryl Tinnerstet as the potential 
distributor for these. My goal is not to profit from these 
personally. My goal is to get rid of TAB's as a concern from a 
safety and reliability standpoint. I need to get a good feel for 
whether there is a demand for these at that price point, so that 
Darryl and I can feel good about investing the money up-front in the 
first batch. I've already "got mine", as do a handful of PNDC 
members. The question is ... what do you want? Peace of mind? 
Or ... not. Please give me some feedback on this.

Toby Peterson, VIN 2248
Winged1

--- In dmcnews@xxxx, Les Huckins <jhuckins@xxxx> wrote:
> I think he's trying to say that he's developed a better bolt is 
that right Toby? Reminds
> me of some of my college Physics classes, I was never too sure what 
was going on there
> either.