20 replies to this topic

[Wirra]

It’s more than three decades since I ‘played’ with cars or did any real hands-on engineering and now that I’m starting the final assembly of my kit car I’ve become aware that all the components I salvaged from the donor car (’05 GM product) were secured without spring washers. All appear to have flat washers integrated with the bolt head or nut,which I assume expedites assembly, but I’m wondering what’s happen to the humble spring washer and what in the design of current fasteners compensates for their function.

Should I be using these bolt in the assembly of my car?

[275 GTB-4]

The problem with split washers is if they split elsewhere (break) under tension....ergh.... you loose tension.

Whereas the slightly oval nut or "nyloc" and with or without integral washer hangs on well...assuming they are good quality in the first place.

Edited by 275 GTB-4, 18 May 2013 - 02:59.

[Magoo]

The spring aka split washer works by digging the sharp cut corner at the split into the surface of the component being joined. So if the surface is harder than the washer, or if the washer has lost its tension, or if the corner is dulled, the locking property is reduced or lost. You may notice when reassembling an um, assembly that the split washer wants to return to the rutted little place where it was previously tightened, which is also to be avoided. When all is said and done, the modern fastener as pictured above is a significant advance in a number of ways.

Edited by Magoo, 18 May 2013 - 03:21.

[malbear]

The spring aka split washer works by digging the sharp cut corner at the split into the surface of the component being joined. So if the surface is harder than the washer, or if the washer has lost its tension, or if the corner is dulled, the locking property is reduced or lost. You may notice when reassembling an um, assembly that the split washer wants to return to the rutted little place where it was previously tightened, which is also to be avoided. When all is said and done, the modern fastener as pictured above is a significant advance in a number of ways.

I am a fan of the marsden nut.
lmarsden nut

[rachael]

Check this page for one of the reasons spring washers are no longer specified;

Bolt Science

Lots more of interest on that website too.

[Greg Locock]

I did a fastener course, based in part on the bolt science material, and in NONE of the joints we analysed did we use spring washers. The only exception I have seen in practice is electrical terminations of soft wire.

[Lee Nicolle]

On non standard applications I use spring washers, often coupled with a flat washer as was common in the 60s and 70s on suspension components. Especially where the bolt is not normally done up to its full torque. eg grade 5 1/2 UNC bolts on suspensions.. No spring washer and they come loose. Unlike many I use them on speedway shocks too. 1/2" NC or NF done up to around 45-50lb will not come loose with a spring washer but is guaranteed too without.
Washer head bolts and nuts are generally ok though after a few uses come loose. Coupled with nyloc or crimp nuts will be ok. BUT, those 'self locking' nuts do not after a few uses. And I always use spring washers with them, as manufacturers did often anyway.
Ideally a spring washer should be used either on the head of a bolt, or with a flat washer. And hold the bolt end with the springy so the washer does not turn and try to get bigger.
On sheet metal they are almost essential as you just nip the bolts and the spring washer stops it loosening. Almost always combined with a large flat washer.
On engines again for limited load items such as alternators etc a spring washer will stop bolts loosening far better than a washer head bolt. A manufacturer while not doing a recall issued a bulletin for this in the late 80s.
The Ford UBS system for accessories was/ is a nice touch. I have never seen one come loose though overtightening will do some collateral damage. Eg On A/C compressors will split the alloy and alloy the gas to leak out. If your lucky some head stud sealer will keep it in,, maybe.
If using a simple bolt and nut though normally a spring washer is still an imperative

[bigleagueslider]

The split ring lock washer was a miserable way to provide a locking function in threaded fastener installations. The idea behind the split ring washer was that it created some axial preload force on the bolt/nut, which helped prevent the fastener from loosening. The principle behind the split ring lock washer was disproved long ago, and they are no longer used for most applications. The flanged bolt and nut shown in your picture likely use an adhesive compound for locking.

[275 GTB-4]

On non standard applications I use spring washers, often coupled with a flat washer as was common in the 60s and 70s on suspension components. Especially where the bolt is not normally done up to its full torque. eg grade 5 1/2 UNC bolts on suspensions.. No spring washer and they come loose. Unlike many I use them on speedway shocks too. 1/2" NC or NF done up to around 45-50lb will not come loose with a spring washer but is guaranteed too without.
Washer head bolts and nuts are generally ok though after a few uses come loose. Coupled with nyloc or crimp nuts will be ok. BUT, those 'self locking' nuts do not after a few uses. And I always use spring washers with them, as manufacturers did often anyway.
Ideally a spring washer should be used either on the head of a bolt, or with a flat washer. And hold the bolt end with the springy so the washer does not turn and try to get bigger.
On sheet metal they are almost essential as you just nip the bolts and the spring washer stops it loosening. Almost always combined with a large flat washer.
On engines again for limited load items such as alternators etc a spring washer will stop bolts loosening far better than a washer head bolt. A manufacturer while not doing a recall issued a bulletin for this in the late 80s.
The Ford UBS system for accessories was/ is a nice touch. I have never seen one come loose though overtightening will do some collateral damage. Eg On A/C compressors will split the alloy and alloy the gas to leak out. If your lucky some head stud sealer will keep it in,, maybe.
If using a simple bolt and nut though normally a spring washer is still an imperative

Maybe you need shake-proof washers on your shockers?

https://www.google.c...o...548&bih=704

or maybe you could lock-wire your nuts

[Tony Matthews]

I fail to see how a flat washer combined with a split washer is going to work. The split washer has 'tangs' that bite into the underneath of the nut and the surface below the nut.

[MatsNorway]

http://www.nord-lock.com/nb/

[Magoo]

I fail to see how a flat washer combined with a split washer is going to work. The split washer has 'tangs' that bite into the underneath of the nut and the surface below the nut.

exactly. The two washers are at cross purposes.

[mariner]

If its safety critical then always go look at what aerospace people do. Their level of safety obsession is much, much higher and and those pesky AN and NAS sizes were done for a good reason as was their rejection of spring washers.

Bolts can be dull but I read that Keith Duckworth's new graduate test question was " desrcibe to me all the forces acting on bolt as it s done up"

I think a comon problem is understanding the crush resistance of the bits being clamped. If its, say aluminium or even wood, then an entirely different locking approach is needed verus two bits of high stength steel.

[mariner]

I have just watched the bolt science video - quite alarming!

It made me think of three things

1) it is always said that bolts are NOT locating devices! Since it seems to be lateral movement which loosens things most then good dowelling should prevent most loosening.

2) The locking mechanisms are all compared to the " worst case " of no locking scheme.

3) Fine but that leads to my questions

- What is the most agressive example of lateral shake - answer a engine flywheel getting constant impluse loads laterally across the bolts.
'
- What bolts dont use washers - many flywheel bolts.

- do all flywheels use dowels to stop lateral movemnet - no

Now I am worired because I've just had to remove and replace the flywheel on my Chevy V-8 with no dowels. I've use ARP bolts and ARP's specified Loctite but there are 6 bolts and , roughly , 600 ft-lbs of torque . So each washerless bolt gets two lateral loads of about 400 lbs across it every 90 degres of rotation.

I hope I did them up right !!!

Edited by mariner, 21 May 2013 - 18:36.

[Magoo]

I have just watched the bolt science video - quite alarming!

It made me think of three things

1) it is always said that bolts are NOT locating devices! Since it seems to be lateral movement which loosens things most then good dowelling should prevent most loosening.

2) The locking mechanisms are all compared to the " worst case " of no locking scheme.

3) Fine but that leads to my questions

- What is the most agressive example of lateral shake - answer a engine flywheel getting constant impluse loads laterally across the bolts.
'
- What bolts dont use washers - many flywheel bolts.

- do all flywheels use dowels to stop lateral movemnet - no

Now I am worired because I've just had to remove and replace the flywheel on my Chevy V-8 with no dowels. I've use ARP bolts and ARP's specified Loctite but there are 6 bolts and , roughly , 600 ft-lbs of torque . So each washerless bolt gets two lateral loads of about 400 lbs across it every 90 degres of rotation.

I hope I did them up right !!!

Since lock washers don't work, I wouldn't worry a lot about not having any. Chemical thread locking is the best locking so you are good to go. Yes, it would be better if the flywheel were doweled but oh well. I have never seen an issue on BBC flywheels when properly assembled with far more grunt than you are running. I encourage you to find something else to worry about.

[gruntguru]

1) it is always said that bolts are NOT locating devices! Since it seems to be lateral movement which loosens things most then good dowelling should prevent most loosening....
...
- do all flywheels use dowels to stop lateral movemnet - no

Some flywheel bolts have a precision shank which is a close fit in the flywheel and crankshaft for location - a de facto dowel.

[Kelpiecross]

Some flywheel bolts have a precision shank which is a close fit in the flywheel and crankshaft for location - a de facto dowel.

Which are usually called "fitted bolts" - at least that is what they are called around here. After a lifetime of using spring washers I doubt if I could bring myself to not using them.

The most unusual self-locking nut I have seen is on the main bearing caps of a Cooper S - the nut is visibly deformed before you put it on and straightens itself out when tightened up. Like all BMC new parts for the S they were fiendishly expensive.

Back in the seventies the motocross riders used "Bear" glue on the nuts and bolts - the glue was referred to as "yellow peril".

I notice this forum now has "spellcheck" - a very good improvement.

[Beamer]

Check this page for one of the reasons spring washers are no longer specified;

Bolt Science

Lots more of interest on that website too.

Nice read, thx!

[gruntguru]

I notis this fourem now has "spellchick" - a vary gud improovment.

Cheers KC

[Tony Matthews]

I thought 'spellcheck' was wrong, but I couldn't think how.

[bigleagueslider]

Some flywheel bolts have a precision shank which is a close fit in the flywheel and crankshaft for location - a de facto dowel.

With any fastener intended to take shear loads, the fastener body must have an interference fit with the hole. Otherwise, the clamped interface will be subject to relative sliding, and will experience fretting damage. Almost every fastener used on an engine (flywheel bolts, conrod bolts/nuts. main cap bolts/studs/nuts, cylinder head bolts/studs/nuts, etc.) all rely on preload for locking function, and to ensure sufficient shear capability by friction across the clamped interface.