Discussion
BogBeast said:
Am I right in thinking that the nuts & bolts used of the suspension are AN8?
No, but they should be.
http://home.comcast.net/~rosenracing4/wsb/html/view.cgi-photo.html--SiteID-680061.html
The factory supplied bolts are grade 8, but the shoulder length is wrong, which allows the threads to make contact with the support areas of the attaching lugs. This will be most critical on the rear toe link attachment points as there is tremendous shear loads as the car accelerates and decelerates. If these bolts weren't origionally highly tightened, I wouldn't be surprised if the holes were not elongated. This will cause the toe of the rear wheels to change constantly.
The replacement bolts are AN8's, probably -22, and -24.
-10 is one inch, -20 is 2 inches, and each number adds 1/8". These numbers reflect shoulder length. Aircraft standards do not allow more than 2 washers to be used at either end of the bolt, and at least 2 threads have to be showing past the nut.
Measure what the shoulder length should be, including washers, and contact Aircraft Spruce in England, and they will calculate the required length. The proper length is having one washer against the head of the bolt, and the threads begining at the outer edge of the mounting lug. Then one washer will allow the nut to tighten without running out of threads.
Jack
Ultima Factory said:
Jack has brought up an interesting topic in a recent posting regarding suspension bolts.
In theory Jack is correct in his post about bolt selection and this is best explained in my favourite bedtime reading “Engineer to Win” by Carroll Smith.
Please note that if aircraft quality bolts are used on the suspension their design tightening torques are far higher that the standard bolt that Ultima supply and this will induce forces that have not been allowed for in the design of the suspension bushes and will result in premature failure of the bushes.
Ted
There are two points that Ted and I do agree on, one strongly,, and one not so strongly. We both love Carroll Smith's books, and I will agree with Ted, that
under normal driving conditions, the factory supplied bolts are adequate. In my opinion, they are 100% safe.
But I still maintain, that the use of incorrect bolts in the toe link area will cause a the problem as stated in the ealier post if they are not torqued sufficiently, and become loose.
We all have our "quirks" when it comes to certain procedures, and forgive me Ted, but using the proper bolts, regardless of the application is one of mine.
A major mis-use of mounting hardware, was the supplied hardware with the Factory Five Cobra I built in 1998. They also use 1/2" bolts for the suspension, but not only is shoulder length wrong, but the thread is course, not fine. The diameter of the bolt is usually smaller on the threads, therefore if the threads are in the mounting area, you will have play. This was even more apparent with the Factory Five hardware.
Since I live 3 miles from Factory Five, don't think that they didn't hear about it. Their reply was something about cost, which with their low end priced kit, I can understand.
What I don't understand is why the torque settings should vary using aircraft bolts or Ultima supplied bolts, as the thread is similar. While I did replace the bolts from Ultima, I did use the Ultima nuts and washers. The quality of the Ultima supplied bolts appears to be very high, just the threads are too long.
The comments I've made about this hardware issue were not made in any way to degrade the thinking and engineering of the Ultima Factory, as I believe as stated previouly, that the bolts are adequate, but with my aircraft training and background, it's just something I cannot change my thinking on, and I put my money where my thoughts were, and spent the extra money.
In all fairness, since the shop where I built the Ultima is at an airport, it was only a 50 yard walk to a supplier to get the aircraft hardware. That makes it much easier.
Ted, maybe we can continue this discussion at Carlisle, where I'm looking forward to meeting you.
Jack
>> Edited by USCANAM on Thursday 6th May 13:38
USCANAM said:
But I still maintain, that the use of incorrect bolts in the toe link area will cause a the problem as stated in the ealier post if they are not torqued sufficiently, and become loose.
Errr... but that's going to be the case with any bolt Jack regardless of whether you think they are 'incorrect' or not?
Stig said:
But I still maintain, that the use of incorrect bolts in the toe link area will cause a the problem as stated in the ealier post if they are not torqued sufficiently, and become loose.
Errr... but that's going to be the case with any bolt Jack regardless of whether you think they are 'incorrect' or not?
Quite true Chris, but in regards to the Ultima suspension, It could be a problem.
Let's look at the construction of the areas where the 1/2" bolts are used.
Where the upper and lower arms of the front and rear suspension attach to the frame, you have a steel spacer that is actually making contact with the lugs. So actually, you have two items that are holding the bushings in place, the force of the nut being tightened, and the increased contact area of the spacer against the lugs which is being held in contact by the bolt and nut assembly. Granted, if this bolt was loose, it would be a problem, albeit minor, and you might not even notice it because of the design.
But, the toe link does not have the same construction design. It's simply a heim bearing (rose joint) being held in by the 1/2" bolt. Granted you have the contact area of the inner race in contact with the lugs, but you have to picture (especially you with the high H.P.)the high shear forces that these bolts are subjected to. Also remember that they are tightened up against a layer of powdercoating, that will diminish in thickness if subjected to any fore and aft movement if the bolt starts to work in the hole, thereby causing the bolt to loosen further. Now what you have is when the car accelerates, your rear wheel will toe in, and when you brake the wheel will toe out.
In the real world am I being overly critical..probably, but who says I live in the real world!! I just know I've constructed it to proper engineering specs.
Jack
Stig said:
In the real world am I being overly critical..probably, but who says I live in the real world!! I just know I've constructed it to proper engineering specs.
Jack
Should that be 'your' engineering specs rather than 'proper'?
Yes, they are "my" specs that I've learned from others smarter and more learned than I.
I've done 15 single engine Atlantic crossings in my plane and ones that I've ferried. Don't think that the result of a failure of one small bolt or fitting crossed my mind while out over the cold Atlantic. That's when you put your faith in the engineers and pilots before me that pioneered and established the technical standards we adhere to.
In my view, I cannot come up with any reason that a high performance automobile should not be built to the same standards as an aircraft.
Nuff said on this subject.
JAck
Interesting thread guys, thankyou for the replies.
So I am assuming that the bolt are 1/2" fine thread & grade 8.8, my local bolt supplier shouldn't have too much problem with that...
Incidently, are there any good online resources for this sort of stuff, I have a basic understanding of grades etc but really would like to understand a bit more..
(blimey, a bolt spotter in the making..)
So I am assuming that the bolt are 1/2" fine thread & grade 8.8, my local bolt supplier shouldn't have too much problem with that...
Incidently, are there any good online resources for this sort of stuff, I have a basic understanding of grades etc but really would like to understand a bit more..
(blimey, a bolt spotter in the making..)
BogBeast said:
Incidently, are there any good online resources for this sort of stuff, I have a basic understanding of grades etc but really would like to understand a bit more..
(blimey, a bolt spotter in the making..)
You might try Carroll Smith's Nuts, Bolts and Fasteners and Plumbing Handbook. It goes into more detail about the different fastener grades and characteristics. Its a great book to add to your library.
I changed out all my suspension bolts, nuts, and washers to AN. The cost is probably 2 to 3 times what you'd pay for grade 8. You have much more thread sticking out the lock nut though, the threads don't touch the bushing sleeve or the frame mounts, and you can get two different thicknesses of washer to fine tune the bolt spacing. The lock nuts are also taller with more surface area. You know your in a different league of fastener when each bolt comes with a rubber boot protector on the threads.
Cheers!
-Mack
p.s. Don't forget to order some torque seal indicator while your at it. Its nice to be able to visually look things over and know that all the bolts are still torqued. Especially usefull on the driveshaft bolts!
Jack //edit// and Mack,
I'm all for using bolts that have a "proper" shoulder as the bearing surface, or however you care to describe having NO threads in the area that is under load or tension. Look for any motorcycle racer and ask them if they have pivot points using any fasteners with threads in the loaded areas. I learned this in the late '70's.
The hard way.
Learning this is why I can no longer race motorcycles. One shoulder, elbow and both wrists can't take the pounding.
Why would you want to use a suspension bolt that is the correct hardness, but has its dia. reduced 15% (by threads) on the last 40% of the bolt? Aircraft grade may be overkill, but think about that shoulder dimension....
Dave
YMMV
>> Edited by just dave on Saturday 8th May 01:32
I'm all for using bolts that have a "proper" shoulder as the bearing surface, or however you care to describe having NO threads in the area that is under load or tension. Look for any motorcycle racer and ask them if they have pivot points using any fasteners with threads in the loaded areas. I learned this in the late '70's.
The hard way.
Learning this is why I can no longer race motorcycles. One shoulder, elbow and both wrists can't take the pounding.
Why would you want to use a suspension bolt that is the correct hardness, but has its dia. reduced 15% (by threads) on the last 40% of the bolt? Aircraft grade may be overkill, but think about that shoulder dimension....
Dave
YMMV
>> Edited by just dave on Saturday 8th May 01:32
just dave said:
Look for any motorcycle racer and ask them if they have pivot points using any fasteners with threads in the loaded areas. I learned this in the late '70's.
The hard way.
Learning this is why I can no longer race motorcycles. One shoulder, elbow and both wrists can't take the pounding.
>> Edited by just dave on Saturday 8th May 01:32
Dave
Would you care to elaborate on what happened
bigmack said:
Incidently, are there any good online resources for this sort of stuff, I have a basic understanding of grades etc but really would like to understand a bit more..
(blimey, a bolt spotter in the making..)
You might try Carroll Smith's Nuts, Bolts and Fasteners and Plumbing Handbook. It goes into more detail about the different fastener grades and characteristics. Its a great book to add to your library.
I changed out all my suspension bolts, nuts, and washers to AN. The cost is probably 2 to 3 times what you'd pay for grade 8. You have much more thread sticking out the lock nut though, the threads don't touch the bushing sleeve or the frame mounts, and you can get two different thicknesses of washer to fine tune the bolt spacing. The lock nuts are also taller with more surface area. You know your in a different league of fastener when each bolt comes with a rubber boot protector on the threads.
Cheers!
-Mack
p.s. Don't forget to order some torque seal indicator while your at it. Its nice to be able to visually look things over and know that all the bolts are still torqued. Especially usefull on the driveshaft bolts!
Excellent. 11 quid on Amazon. Cheers Mack
Stig said:
Should that be 'your' engineering specs rather than 'proper'?
I think that "established engineering best practice" would have been more appropriate phrasing.
Ted's point that the Ultima suspension is overengineered to allow for the fact that it is assembled by novice car builders, lives on the road with potholes, has to be possible to safely replace with commodity parts is a very important one though. If the suspension were to rely on a highly customised aircraft spec bolt...you can bet some well meaning amateur car builder will replace it with a substandard part...and come to a sticky end.
It would be nice to have bolts with the correct shoulder though. Does anyone know of a good mail order bolt supplier in the UK to buy this kind of fairly specialised stuff? OTOH We've got a hell of a big motorsport industry here. Where do they get their fasteners?
davefiddes said:
It would be nice to have bolts with the correct shoulder though. Does anyone know of a good mail order bolt supplier in the UK to buy this kind of fairly specialised stuff? OTOH We've got a hell of a big motorsport industry here. Where do they get their fasteners?
www.aircraftspruce.com/home.php
One of their locations is near London
USCANAM said:And, if you have not been to McMaster Carr, you should check it out...they have just about everything under the sun. However, I don't know if they have a location anywhere in GB.
It would be nice to have bolts with the correct shoulder though. Does anyone know of a good mail order bolt supplier in the UK to buy this kind of fairly specialised stuff? OTOH We've got a hell of a big motorsport industry here. Where do they get their fasteners?
www.aircraftspruce.com/home.php
One of their locations is near London
-- Scott
Reno, NV
davefiddes said:
It would be nice to have bolts with the correct shoulder though. Does anyone know of a good mail order bolt supplier in the UK to buy this kind of fairly specialised stuff? OTOH We've got a hell of a big motorsport industry here. Where do they get their fasteners?
So far I have found:
www.tridentracing.co.uk/info/fastas.htm
and edited for NAS:
www.coastfab.com/tech%20info.html
www.sky-craft.co.uk/an8_bolts.htm
www.aerofast.co.uk/products.htm
Haven't contacted them yet as I'm still trying to get my metric head around fractional imperial measurement..
Also found this:
www.zenithair.com/kit-data/ra/hardware.html
and the Pegasus catalogue contains all the AN pn's
>> Edited by BogBeast on Sunday 9th May 13:40
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