Will have to start somewhere

more fun today-and a question

After spending way too much time on the left side rear shock brace which by the way should not be attempted by anyone who values their back or wishes to walk like they don't have a roll of Susan B. Anthony's up their ........ for the next week, I turned my attention to some more mundane tasks; In an effort not to stray too far from originality which, yes, is a very slippery slope I decided that although the air cleaner and vent fan cover were peppered with imperfections they should be cleaned and not re-painted. The under-hood area needs to be repainted because the corrosion dictates such, but my hope is to preserve the aged look of the entire car as long as it is not detrimental to its health-so to speak. I won't re-chrome anything as long as it's not rotting, etc. On another note (shot) I had a heck of a time getting the elephant skin on the passenger side without some wrinkles. Not sure why but the driver side looks good and the other side well, could look better. Still hoping to get some feedback on the shock braces before I spend another 3-4 hours making the other side. Also spent a fair amount of time clearing the sunroof drains- gentle persuasion with a coat hanger and lots of air back and forth.

Reminds me, question, the hood latches that are close to the windshield (attached to the hood) are those usually flat black or are they painted the same color as the hood? Mine are a rather flat black so I'm just wondering if those need to be painted too?

Thanks-
 

Attachments

  • passenger trunk.jpg
    passenger trunk.jpg
    74.8 KB · Views: 225
  • old parts.jpg
    old parts.jpg
    93.4 KB · Views: 215
guys, think about putting a sheet of a thin material in a frame (under tension) a sheet of plastic, and push on it with a blunt object. it won't tear from the edge - it will deform (under tension) until it punches thru. paper will punch thru then tear (not much deformation due to shear). sheet metal is more similar to paper than the plastic - it deforms a little until the modulus of elasticity gives out and it breaks. in this case, thickness is the determining factor that reduces the shear force as well as the tension deformation. now consider the washer or dish on top of the shock mount - the further the distance from the "point" load - that the thickness extends, the more it disperses the tensile load ... and it reduces the effective load per square inch (or centimeter).

we have to resist the two separate forces - tension (the surface elongating across the top of the mount) and shear (the surface breaking off or punching thru). shear multiplies due to distance from the load point - since the load that the steel will withstand is measured in reference to the material's thickness, the thicker it is, the more shear force it will withstand.

the washer or dish at the top of the shock mount will always be in tension. - the wider it is, the more tension force it will resist by distributing the load - so a 1" washer will only add a slight give a certain amount of tension distribution. a 2" washer or dish has twice the circumference - so it will distribute twice the tension force. a 3 inch diameter will resist 3 times the tension of the 1", and so on.

so now think of this in terms of thickness. a 1" diameter with a 1/8" thickness should have approx. twice the tensile strength as a 1/16" thickness - so a 1/8" - 1" diameter would theoretically resist the same tension as a 2" - 1/16" thick material. the danger of the last discussion is that 1/16" thick material will no longer be governed by tension, it will likely be governed by shear.
 
Peter Coomaraswamy said:
After spending way too much time on the left side rear shock brace which by the way should not be attempted by anyone who values their back or wishes to walk like they don't have a roll of Susan B. Anthony's up their ........ for the next week, I turned my attention to some more mundane tasks; In an effort not to stray too far from originality which, yes, is a very slippery slope I decided that although the air cleaner and vent fan cover were peppered with imperfections they should be cleaned and not re-painted. The under-hood area needs to be repainted because the corrosion dictates such, but my hope is to preserve the aged look of the entire car as long as it is not detrimental to its health-so to speak. I won't re-chrome anything as long as it's not rotting, etc. On another note (shot) I had a heck of a time getting the elephant skin on the passenger side without some wrinkles. Not sure why but the driver side looks good and the other side well, could look better. Still hoping to get some feedback on the shock braces before I spend another 3-4 hours making the other side. Also spent a fair amount of time clearing the sunroof drains- gentle persuasion with a coat hanger and lots of air back and forth.

Reminds me, question, the hood latches that are close to the windshield (attached to the hood) are those usually flat black or are they painted the same color as the hood? Mine are a rather flat black so I'm just wondering if those need to be painted too?

Thanks-
Click to expand...
i have a new pair of hood latches - unfinished. the latches on my car are painted to match the car, but i always thought that was laziness on the part of the painter. so anybody know the answer?

thought - cleaning sunroof drains - how about using a thick fishing line, a tennis string or a piece of flexible stainless steel cable (i have some left over from my sailboats). something that is thick enough to go down the hose ... but is thick enough to push down straight.
 
OK, so

Fishing line, good idea, I'll probably substitute with some thick weed-wacker cord, hood latches black, previous painter not lazy, RS, so, what you are saying is that if I put a BIG washer inside the shock holder from underneath, 3X the diameter of the standard washer then my shock holder will withstand 3X the upward force thus averting a possible "Steve" issue? If that is the case I would surely prefer to do that than fab another one of those braces. Please advise as currently both holders are in very good condition.

Thanks all!!!
 
Peter Coomaraswamy said:
Fishing line, good idea, I'll probably substitute with some thick weed-wacker cord, hood latches black, previous painter not lazy, RS, so, what you are saying is that if I put a BIG washer inside the shock holder from underneath, 3X the diameter of the standard washer then my shock holder will withstand 3X the upward force thus averting a possible "Steve" issue? If that is the case I would surely prefer to do that than fab another one of those braces. Please advise as currently both holders are in very good condition.

Thanks all!!!
Click to expand...
Peter,

i have not calculated the load or size of the washer required - as i do not know what forces that you have to withstand. sorry to be vague - but i just don't know the answer - just the science.

you are trying to resist shear force as well as tensile forces. the bigger the washer is, the more it spreads out the tensile load ... as circumference works off of Pi, then it works of of that factor (pi x diameter). so yes the larger washer will distribute the tensile forces significantly better. but as i also said - that is not the only force you have to deal with - you have to resist shear / punch thru. that force is best resisted by thickness.

my point is, you could use a 3" diameter / 1/16" thickness washer - and it could still fail - as it could punch thru if the washer failed due to shear.

weed wacker cord - perfect. my latches are black too ... but so is my car.
 
Another job to do twice, looks like I'll be removing the rear shocks and fitting a washer of larger diameter on the underside, however, since I already fabricated the outer brace and it's small and is completely hidden by the elephant skin, I will use that as well that way I can be reasonably assured that I won't punch through the mounts. Would just hate to do the job 3 times :) Now, maybe I can start putting that darn trunk together and start on the engine and finish up the engine bay. I'm waiting on a couple more parts from Ben/Carl which should arrive today- then it's just a matter of time.

Thanks all!

RS, thanks, it's taking my brain a little bit longer these days to absorb knowledge but I think I understand a little- much appreciated.
 
I had a large washer under the bottom. The thin metal on top needs reinforcement somehow.

Peter Coomaraswamy said:
Another job to do twice, looks like I'll be removing the rear shocks and fitting a washer of larger diameter on the underside, however, since I already fabricated the outer brace and it's small and is completely hidden by the elephant skin, I will use that as well that way I can be reasonably assured that I won't punch through the mounts. Would just hate to do the job 3 times :) Now, maybe I can start putting that darn trunk together and start on the engine and finish up the engine bay. I'm waiting on a couple more parts from Ben/Carl which should arrive today- then it's just a matter of time.

Thanks all!

RS, thanks, it's taking my brain a little bit longer these days to absorb knowledge but I think I understand a little- much appreciated.
Click to expand...
 
Stevehose said:
I had a large washer under the bottom. The thin metal on top needs reinforcement somehow.
Click to expand...
Steve, if you had a large washer underneath ... was it welded to the body, or just part of the bolt sandwich? i was actually wondering if that would work - i guess that answers that question.
 
No just a sandwich, I thought it would spread the load away from the spot welds. Obviously did not work :razz:

rsporsche said:
Steve, if you had a large washer underneath ... was it welded to the body, or just part of the bolt sandwich? i was actually wondering if that would work - i guess that answers that question.
Click to expand...
 
follow-up question - how big of a washer? if the washer was less than 1 1/2" diameter, that is why you got a big rip when the fatigued body metal gave way.

my guess is that we need to weld a dish (cap) or maybe weld a bigger washer underneath ... so that the metal acts together.
 
3" washer

rsporsche said:
follow-up question - how big of a washer? if the washer was less than 1 1/2" diameter, that is why you got a big rip when the fatigued body metal gave way.

my guess is that we need to weld a dish (cap) or maybe weld a bigger washer underneath ... so that the metal acts together.
Click to expand...
 
hmmm ... new quote - bigasswasher. okay, i'm officially out of ideas other than metal fatigue and the spot welds gave way.
 
I agree with you that something split apart starting a Titanic-like chain reaction tearing of the structure.

rsporsche said:
hmmm ... new quote - bigasswasher. okay, i'm officially out of ideas other than metal fatigue and the spot welds gave way.
Click to expand...
 
Pre welding: Supports are made and I came up with a little idea to position the supports properly, I used an outer front wheel bearing race and the stock washer to hold the top of the brace flat against the 1/16 inch thick stock washer on top of the shock can. The new steel is 1/8 inch and the side straps are 1-1/2 inches wide and the top "washer" is 3 inches in diameter with a 1-1/8 hole drilled in the center which clears the stock Bilstein washer so once in place the shock can be changed, bushing and all. Pictures attached-
 

Attachments

  • shock support.jpg
    shock support.jpg
    61.2 KB · Views: 200
  • shock support1.jpg
    shock support1.jpg
    62.2 KB · Views: 201
Peter Coomaraswamy said:
Pre welding: Supports are made and I came up with a little idea to position the supports properly, I used an outer front wheel bearing race and the stock washer to hold the top of the brace flat against the 1/16 inch thick stock washer on top of the shock can. The new steel is 1/8 inch and the side straps are 1-1/2 inches wide and the top "washer" is 3 inches in diameter with a 1-1/8 hole drilled in the center which clears the stock Bilstein washer so once in place the shock can be changed, bushing and all. Pictures attached-
Click to expand...
looks good Peter ... so question on behalf of all of us. when are you going to go into production of these units to help protect all of the rest of us?

we know it will be after you complete the rebirth of the polaris coupe.
 
You will all have to wait until I find a small but attractive Polynesian woman to walk on my back for a week, and if she happens to have a taste for the "unusual" it may take a bit longer. I can do the specs but I would like to also run them by others on the forum in case I'm doing anything that is not as effective as it could be. I'm welding them in in a few minutes so let's see how that goes- Anything could happen:oops:
 
You must log in or register to reply here.
Back
Top