So, i broke a Grade 8 bolt........

I've read the hardware stainless bolts fall between a grade 5 and a grade 8 for strength.

 

Oh Fuck... I'm crawlin under the desk until THIS blows over....

 

...and your set up does look mighty fine. I will apologise for my 'ratrod 2003' look ahead of time. I was going more for the 'ratrod 2006' look but I obviously missed it.

Out of date before it hits the road ...

Pete

 

Hot rodders have been using spring hangers/perches fabricated from bolts and tubing for years.

Both speedway and Total Performance use them in the suspension systems they sell:

http://www.speedwaymotors.com/xq/aspx/paging.yes/dept_id.367/display_id.3308/qx/Product.htm

http://www.tperformance.com/street_rod_store/front_suspension/spring_mounts/

I don't think they would be in business if they had a reputation for killing off their customers.

I could have fabricated the perches here. But I went with Bob because I trust his judgement and his welds.

 

I don't know Bob or his reputation, so I speak only about what I see in the pictures, and what I see is scary engineering & fabrication. That welded-on bolt has been heat-treated to something other than Grade 8 for some or all of it's length. The welds look globby and I'd guess he only got partial penetration into the tube. Putting a cyclical bending load on brittle weld (assuming they weren't carefully annealed) scares me. I'm not saying I can weld any better, but I'd never drive on that, no matter how light my car was.

As as for Speedway, they can sell whatever they want. Doesn't mean it's good or bad. They offer it in a chromed version, too, and I wouldn't dream of putting a chromed bolt in a suspension part. I don't have enough faith in a mail order hot rod catalog to understand hydrogen embrittlement and make sure their suppliers prevent it.

 

I don't know much about your ride or how it is built but I'm going to suggest that the bolt wasd defective. A 1/2" grade 8 bolt should hold up just fine in the type fo situation that you describe.

Where did it break? the most natural place for it to break is where the threads meet the shank unless your threads are at a shear point, the threaded part of the bolt is its weakest [place, if you had cut threads that makes them even worse.

What you want is shank at the shear point and threads only outside of that area. i usually try and set my suspensions up so that the shank of the bolt passes through whatever is being bolted and then use a flat washwer out side of that to take up the space between the threads and the mateing surface for the nut.

 

any one here able to tell me if i'm gonna die on my set up i have a picture of a set of mock up bones with old batwings done exactly as my new shit was done . here. i had my fab guy take a set of total performance bolton spring perches and cut a large diameter whole in the outside of the bone and a smaller (bolt size) diameter whole in the inside and insert the perch through the bone . he then welded all around the outside and then went to the inside and instead of threading a nut on there he cut the bolt threads off about an 1/8th" from the inside surface and went all around that area with a weld . any opinions on this from the metal masters ???it seems perfectly fine to me and i'm gonna run em. but i'd like to know what ya'll think.

i thought i had a picture in my computer but i don't . i'm gonna have to take one tomorrow and i'll post it

thanx
jp

 

The bolt at the top was the one that came out of the other side....The broken one was identical.

...The break is exactly where the perch lies flat against the bone.....If you read one of my other posts it says that when i went to assemble it with the new bolt, i had to loosen the jamb nuts on the bone and the drag link to pull the axle back about 1/4" to 3/8" so i could line up the bolt going through the bone and into the perch, meaning that there was some foward pre-load on that bolt.....Now, was that enough to cause this?.....I don't know, but i can't imagine it helping the situation


What your saying about the bolts makes a lotta sense, but it almost sounds like you need custom bolts, since i need a 1'2" x 1 3/4" bolt with at least a 1/ 1/4" shank......My brother works in the aviation field and if this sucker was fine thread, any size bolt wouldn't be a problem

 

does this broken bolt go from the outside of the bone and thread into a nut thats welded onto the shackle part??

 

AN bolts are available in every 1/8" increment of shank, with just enough threads for a washer and nut. They are avail. in coarse thread for special applications (read: more money ). I would recommend counter-boring about 1/2" of threads out of the perch, reaming it to size and then get a bolt with enough shank to go all the way in there. That way the shank is carrying a lot of the side load instead of the thread. We do this on all the critical single shear attachments on the race car, and have yet to have a failure other than crash damage...
Just my .02...

 

That bolt is being used IMPROPERLY! Bad design. Get Carrol Smith's books "Nuts Bolts Fasteners and Plumbing" and "Engineer to Win" and read them to see how bolts should be used.

 

Where?....I've looked online and don't see any descriptions of shank lengths

 

I have a Lawson Products catalogue here at work and have the part numbers for the supertanium bolts that Roy was talking about if any one needs numbers for them.

 

Different types of fasteners: http://www.coastfab.com/boltsseries.html

General Info on AN bolts: http://www.coastfab.com/pdf/an3-an20%20genspecs.pdf

Available lengths: http://www.coastfab.com/pdf/an3-an20%20chart.pdf

There's a page on their site that has whats in stock, but I lost the link and couldn't find it again.

Hope this helps.

 

??????????????????????????????????????????????????????

 

PS, They're actually avail. in 1/16ths, that's what the number after the hyphen is. It is the shank length (no thds), NOT overall length like hardware store bolts.

 

Ding, ding, ding........We have a winner!......

I didn't put this thing together....yep, just three threads per side holding it together....Have longer bolts in now temporarily but am working on getting the bolts with the right shanks........

 

bolts with the right shanks ain't gonna do you shit. you're just rockin that perch on those threads..

That bolt is being used wrong. Time to lookup at Blownolds post, find that book and have a read... doesn't matter if you built it or not... you need to fix it right!

buy perch bolts and slide em through your bones. I wouldn't use the welded style shown above.

 

Good advice.

There is NO WAY I would trust a 1/2" coarse bolt in single shear supporting the load of your front end.

As for the coarse thread being stronger than fine thread it depends. If its in shear then coarse isn't stronger because the root diameter is smaller on a coarse thread bolt so it will shear before a fine thread. If it is threaded into a weaker material where the material will fail before the bolt in tension (strip, pull out, whatever you want to call it) Then a coarse bolt is the better choice. This was all mentioned earlier.

As for stainless, if I remember correctly (don't quote me exactly, I don't have a design book handy) 316 stainless has about a 35 ksi tensile strength, whereas mild steel is 36 ksi. Grade 5 and 8 are much higher. There are grades of stainless that don't necessarily have the corrosion resistance but have much higher strengths. For the most part all a hardware store has is 300 series stainless. This also was said earlier.

Bolt strength, size, thread type, and material construction needed varies a great deal depending on the loading.

 

Is this what you mean? Crude drawing, but the shear point is now on the shank which is the proper way......The bung that the bolt goes into is tapered, i would imagine for the taper on the bolt to fit into.......

 

Longer bolts will not help, as stated above. The design is unsafe. DO NOT DRIVE the car.
Quickest and easiest fix would be to buy a pair of early ford perch bolts, drill right through the bones, pass the new perch right through the bones and weld both sides (really well, no pigeon shit) then cut off the excess bolt that's sticking out.
Be sensible, be safe.
Mart.
PS if the person that built that front end was responsible for the rest of the car I'd have a good look around the rest of it.
M.

 

Some one has probably already pointed this out but that's a corse thread bolt. You don't have anyway near enough thread in the socket and to get it the way I explained earlier you just get a longer bolt and cut some of the threaded part off. The longer bolt will have more smooth shank.

DOH I just saw your drawing, yes that's the shear point where the two pieces of metal that can slip past each other meet. A lot of the felas are useing a apring perch that has its own bolt that passes trhough the bone with a nut on the other side. I think a stock A perch bolt comes pretty close to matching up.

 

Another thing that scares me is that there is no positive way of locking the bolt into place. Are you using some locktite? Me I would drill the head for a safety wire so it wont work loose. But that is the Aircraft mech in me talking.

Dawg

 

Okay, so can i use one of these?.....It's too long but cut it flush and weld both sides?......The hole it's going through id double walled.....Still need a sleeve?......Also, need a 29x1 3/4 main leaf......Anyone sell single leafs?

 

If you are going to weld the perch bolt right to the bone then a sleeve won't be needed. Sleeves or bushings are to support the bone with a hole in it. The perch bolt will do the same thing. If you want to be able to remove the bolt for some reason then a nice tight bushing welded on both sides would be in order, then a good quality locking nut. I say get a new spring, perch bolts and shackles from Posies (fast delivery to our area and excel. quality), set up your perch bolts nice and straight and weld 'um right to the bones. Tig them if you can or have someone do it for you to be sure there is a good,clean penetrating weld.

 

I've twisted a 3/8" grade 8 bolt off by hand, might even of been a 1/2" using a 1/2" drive before and no cheater bar. I have a problem of "it can go a little tighter..."

 

I admittedly didn't read to the end of the thread, so if my following two points have been covered please ignore...

I believe hydrogen embrittlement issues can arise from yellow zinc plated hardware as well. Regarding design, be sure that all of the shear planes in your application are in the shank of the bolt. I made the mistake once of placing a shear plane at the transition between the shank and the threads, after breaking a couple of bolts in testing I put in a longer bolt and fixed the issue.