smart51
|
| posted on 1/1/06 at 06:32 PM |
|
|
Sierra Lobro drive shaft bolt failure
The bolts holding the lobro shaft to my rear right wheel broke today. 4 of them came loose and two then snapped. There was a Clonking noise and a
loss of power, just before a layby, luckily and only 3 or 4 miles away from home.
My wife brought me a trolley jack and I put back in the 3 remaining good bolts and drove home slowly. The broken stud came out alright and there is
no real damage, I just need a full set on new bolts now.
It seemed that I hadn't put threadlock on this end. I checked the others whilst I was under the car and they were all tight and threadlocked.
It seems the shake proof washers on their own are not enough.
It seems like a weak design to me, only the bolts hodling the shafts on and transmitting all the power. Not fail safe really.
Are the 12.9 cap head bolts that I used a good enough spec?
What is the best way to clean the threads prior to applying threadlock?
How much threadlock should I have used?
I'll go round and check ALL the bolts on the car for tightness tomorrow.
|
|
|
|
|
amalyos
|
| posted on 1/1/06 at 06:57 PM |
|
|
I'm sure the std bolts are 12.9 quality, they should be OK. (I'm just about to order some for my build so I hope so!!!)
I did notice the doner I used had some loose bolts.
An idea may be to fit and torque them up (to stretch them) without threadlock, then remove them an apply threadlock after, but they do need to be free
of any grease, try using a good degreaser or thinners maybe.
Steve.
|
|
|
Wadders
|
| posted on 1/1/06 at 06:59 PM |
|
|
To be fair i think you should use the genuine ford tab washer thingies, its virtually impossible to clean the threads properly for threadlock,because
the bolts pick up grease from the lobros as you assemble them. Saying that i've had no problems since i fitted spring washers, although i do
check them regularly. Grade 12.9 is fine btw.
Originally posted by smart51
The bolts holding the lobro shaft to my rear right wheel broke today. 4 of them came loose and two then snapped. There was a Clonking noise and a
loss of power, just before a layby, luckily and only 3 or 4 miles away from home.
My wife brought me a trolley jack and I put back in the 3 remaining good bolts and drove home slowly. The broken stud came out alright and there is
no real damage, I just need a full set on new bolts now.
It seemed that I hadn't put threadlock on this end. I checked the others whilst I was under the car and they were all tight and threadlocked.
It seems the shake proof washers on their own are not enough.
It seems like a weak design to me, only the bolts hodling the shafts on and transmitting all the power. Not fail safe really.
Are the 12.9 cap head bolts that I used a good enough spec?
What is the best way to clean the threads prior to applying threadlock?
How much threadlock should I have used?
I'll go round and check ALL the bolts on the car for tightness tomorrow.
|
|
|
steve_gus
|
| posted on 1/1/06 at 07:11 PM |
|
|
Ford used these joints on sierra and granada and there must have been about a gadzullion made - and I dont think that your problem was common or we
would have heard about it.
Anyways, the propshaft drive flange to the diff also only attaches by two flat surfaces and four bolts..... I wouldnt mind betting thats standard
practice....
I have to refit a shaft on my car soon, and I dont have enougth bolts. (Had to cut them as the T40 bit just shatters on these old bolts) So, im gonna
buy 6 bolts and three of the locktab thingys from a ford dealer - i dont expect them to be that expensive......
atb
steve
http://www.locostbuilder.co.uk
Just knock off the 's'!
|
|
|
aerobrick
|
| posted on 1/1/06 at 08:56 PM |
|
|
Hi i am building an f27 but mainly i am on the ford sierra owners club website got lots of info on ford bits there good bunch of guys and gals.
As for lobro bolt failure its the 1st time i have heard about it and some of the cars are seriously modded .
The replacement bolts and lock tabs are still available and pretty cheap best to change the lot .
I have found that cleaning out the holes with carb cleaner helps then sealing the holes with masking tape to prevent grease etc to get in prior to
final assembly
helps.
Oh dont bother getting them off ebay cos all they try and do is add cossie tax  and you dont know how good the spec is.
|
|
|
twinturbo
|
| posted on 2/1/06 at 08:08 AM |
|
|
With Aero here, Also a sierra club member.
Ford don't actualy supply a locktab it's just a flat plate with holse for two bolts, I am not sure what purpose it servers other than to
prevent the bolt head chewing up the shaft surface.
I have run a car 1000's of miles with two missing without a problem.
And the same bolts are used on cosworths producing 500BHP+
I have snapped and twisted 3 T40's getting them out but they have never been threadlocked. Once the head is ground and the shaft removed they
usualy twist out by finger.
Ford do a T45 version of the bolt apparantly which is obviously better for un/doing..
TT
|
|
|
twinturbo
|
| posted on 2/1/06 at 08:09 AM |
|
|
P.s.
An impact driver and a 5lb hammer is a good idea when trying to remove...
TT
|
|
|
bob
|
| posted on 2/1/06 at 10:22 AM |
|
|
The banana shape two hole washer/tabs on the bolt on drive shafts are there to spread the load of the bolts,i was told by a local ford mechanic not to
over tighten these bolts as it is possible to crush the case of the cv joint.
The torque setting for the bolts is less than people would think at 38 to 43 Nm 28 to 32 lb ft
|
|
|
Avoneer
|
| posted on 2/1/06 at 10:25 AM |
|
|
Hi Mr Smart51,
Sorry to hear about that.
The bolts were good quality from my local bolt place and I have used the same ones/type for various apps without failure.
I also know several cars that only use these with the "frilly" washers.
Very rare that you hear of them working loose/snapping.
Were they torqued up right and not just FT?
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
|
|
|
smart51
|
| posted on 2/1/06 at 10:27 AM |
|
|
quote:
Originally posted by bob
The torque setting for the bolts is less than people would think at 38 to 43 Nm 28 to 32 lb ft
How, then, do you stop them coming loose?
|
|
|
Avoneer
|
| posted on 2/1/06 at 10:27 AM |
|
|
I'd use the same bolts again, but drill a 1mm hole through the wall of the head and lock wire pairs together.
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
|
|
|
RichieC
|
| posted on 2/1/06 at 10:29 AM |
|
|
For all there should be no requirement to do that, it will definately prevent them coming loose, might also help with peace of mind. Still not sure
why some worked out and some snapped.
Ill be using the banana shaped spreaders I think in the same way as Ford did.
Rgds
Rich
|
|
|
bob
|
| posted on 2/1/06 at 10:43 AM |
|
|
quote:
Originally posted by smart51
quote:
Originally posted by bob
The torque setting for the bolts is less than people would think at 38 to 43 Nm 28 to 32 lb ft
How, then, do you stop them coming loose?
Threadlock has worked for me,before re fitting i did degrease the new bolts so as not to infect ot weaken the threadlock.
|
|
|
Jon Ison
|
| posted on 2/1/06 at 11:12 AM |
|
|
I'll start by saying "dont use frilly washers"
Ive used frilly washers with no probs for 3 years on two cars that have seen serious road and track work............
And i will finish by saying "dont use frilly washers"
If I said jump off a cliff.........
|
|
|
smart51
|
| posted on 2/1/06 at 02:59 PM |
|
|
quote:
Originally posted by Jon Ison
I'll start by saying "dont use frilly washers"
Ive used frilly washers with no probs for 3 years on two cars that have seen serious road and track work............
And i will finish by saying "dont use frilly washers"
If I said jump off a cliff.........
Cryptic
|
|
|
NS Dev
|
| posted on 2/1/06 at 03:38 PM |
|
|
quote:
Originally posted by Jon Ison
I'll start by saying "dont use frilly washers"
Ive used frilly washers with no probs for 3 years on two cars that have seen serious road and track work............
And i will finish by saying "dont use frilly washers"
If I said jump off a cliff.........
I'LL START BY AGREEING!!
EITHER: Clean the threads, then lightly oil them and torque them up to the correct torque (which I think is considerably higher than I saw mentioned
further up the thread but I don't have the figure handy. It's certainly more than you can do with an allen key!)
OR: Clean and loctite the threads and do the same.
I have NEVER had these come loose, when fitted to a car which has a locked diff and will twist it's driveshafts through 90 degrees, and I used
NO washers at all and no load spreader plates either.
|
|
|
RichieC
|
| posted on 2/1/06 at 03:41 PM |
|
|
Do I remember you saying you had done some destruction testing on these bolts Dev? Im sure you said you ran them tighter than Haynes reckon?
Rich
edited to add previous thread
[Edited on 2/1/06 by RichieC]
|
|
|
Jon Ison
|
| posted on 2/1/06 at 04:02 PM |
|
|
quote:
Originally posted by smart51
quote:
Originally posted by Jon Ison
I'll start by saying "don't use frilly washers"
Ive used frilly washers with no probs for 3 years on two cars that have seen serious road and track work............
And i will finish by saying "dont use frilly washers"
If I said jump off a cliff.........
Cryptic
It wouldn't be that cryptic if you had read a thread from many moons ago when frilly washers or no washers but only ford spready things was the
only way too go, hence "don't use frilly washers" as I don't want too recommend them just let people know Ive had no probs
with them even though you shouldn't use them, does that make any sense ? prob not, clear as mud then.
|
|
|
Avoneer
|
| posted on 2/1/06 at 04:10 PM |
|
|
I think what Jon is trying to say is that he uses them with no problems.
I took his advice on this one as if anyone knows how to test things to destrucion, it must be Jon.
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
|
|
|
bob
|
| posted on 2/1/06 at 05:53 PM |
|
|
NS Dev
I 'm just quoting what the haynes said re torque levels on the bolts,local garage agreed it seems low but mine havnt come loose although i doubt
very much my torque wrench is perfect.
Like said earlier if everything is clean and threadlocked everything should be fine.
|
|
|
jono_misfit
|
| posted on 2/1/06 at 06:05 PM |
|
|
Were the bolts definatley torqued correctly when fitted orriginally?
Ive taken quite a few of these apart, all you should do is replace them with the equivilent strength bolt and do them to the required torque.
One thing to do is make sure the banana washer thing is propperly free from rust on both faces. If its not it can fret abit and reduce the clamping
torque of the bolt and when that happens they may loosen and fall out.
On the subject of lock wire, im pretty sure it doesnt stop things loosening off it just stops them falling out. You can often see a big change in
clamping torque for a small rotation of the bolt.
A good book to read on the subject is "Nuts bolts and fastners" by Carrol Smith. Covers most things you'd ever want to know about
bolts in great detail.
jono
[Edited on 2/1/06 by jono_misfit]
|
|
|
RichieC
|
| posted on 2/1/06 at 06:41 PM |
|
|
Providing wire locking is done correctly (ie not antilocked) the bolt is prevented from rotating and therefore slackening.
Rich
|
|
|
Avoneer
|
| posted on 2/1/06 at 07:33 PM |
|
|
Yep - two bolts tightly (and correctly) lockwired together would prevent either of them turning.
And would provide extra piece of mind.
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
|
|
|
Stu16v
|
| posted on 2/1/06 at 08:03 PM |
|
|
A lot of the time, it isnt the bolts coming loose that is the (initial) problem. It is the loss of clamping force - and that may occur for a number of
reasons...
As mentioned above, make sure the 'banana shaped washer things' are spotlessly clean, no damage etc. This equally applies for the whole
'lobro-joint-to-flange' assembly. Even the finest coating of paint on one mating surface can cause havoc when things get warm for the
first time, and the paint softens. Also, some CV boot kits/CV joints are supplied with paper gaskets. On NO account should these be used, as the
gaskets will compress, and again lose clamping force -make sure all of the mating surfaces are damage free metal to metal only.
It is sadly a more common thing than most here would believe, and often occurs after a new build, or disturbance. With care, and a regular spanner
check for the first few times of use, they shouldnt be a thing to worry about. The use of frilly washers shouldn't be necessary, and may also
possibly affect clamping force. Others have used them with success, but YMMV...
[Edited on 2/1/06 by Stu16v]
Dont just build it.....make it!
|
|
|
NS Dev
|
| posted on 2/1/06 at 10:28 PM |
|
|
quote:
Originally posted by RichieC
Do I remember you saying you had done some destruction testing on these bolts Dev? Im sure you said you ran them tighter than Haynes reckon?
Rich
edited to add previous thread
[Edited on 2/1/06 by RichieC]
Aha!!
Cheers mate!
Yes I did do that and the figures are as per the thread you nicely linked!
Stu's advice is also spot on, everything needs to be cleaned in solvent etc before assembly. I molg grease the joint then clean off around it
with brake cleaner before assembly.
|
|
|
%20(WinCE).JPG)
fastavatar.jpg){kind=avatar}
