Monday, Dec 15, 2003 at 15:58
Hi All
This business of using the tow bar to snatch from worries the hell out of me.
See post 9066 for further discussion about various issues of snatch points.
But lets just clarify somthing here, Example - My heavy duty Toyota branded / supplied tow bar on my Landcrusier is rated at 3500 KG or 3.5 tonnes same as a Reece Hitch.
It is Probably made by Reece with a Toyota Label on it. Anyway that is beside the point.
The Tow hitch is Designed to pull a weight of up to 3500 KG in a largely fore and aft direction, I am sure it has a safety factor built in exactly what I am not sure maybe 20 %.
I continually read about connecting a snatch strap with a safe working load of 8000 KG or 8 tonne to a rated bar of 3500 KG.
Remember the strap also has a safety factor built in again I am not sure what it may be but assume it's 20% or 1600 KG.
I read constantly about snatch straps breaking assuming it is not because of a weakness in the strap itself due to age or whatever, then it has to be assumed it is because of exceeding the safe working limit of the strap.
Even if you do not break the strap it is not unrealistic to consider that you have to be exceeding the load rating of the tow bar virtually each time you snatch.
I base this on each vehicle weighing 2 tonnes that's 4 tonnes in total plus the load for resistance caused by the medium that one vehicle is bogged in, You pick a figure 1 tonne 2 tonne whatever.
Bottom line I would think that most snatches would involve loads of 5 to 8 tonnes without much difficulty.
My point is what sort of stress related damage may this sort of work be doing to the tow hitch assembly and consider when you find out what damage may have been done it might be when your trailor glides past you on the road and hits another car head on or the bar leaves the back of your vehicle and parks itself in the front windsreen of the car you are snatching out. (With snatch strap attached)
In the field I work in we conduct heavy lifts and and I have seen the results of lifing slings and cables that have parted for various reasons the force involved is unreal and if you are in the way
well it's not a nice situation.
I have raised these concerns in prior posts about rated snatch points not to be funny but because I have a real concern about this situation continuing.
Your Tow bar is not designed or rated for this sort of work, the fact that it is common to use it as such means we as a group of users should consider ourselves lucky that perhaps no one has yet had a failure that we know about causing injury or death.
Hence why I believe we all should ensure we have proper rated snatch points fitted to our vehicles.
Regards
John
AnswerID:
40252
Follow Up By: Member -BJ (Sydney) - Monday, Dec 15, 2003 at 17:05
Monday, Dec 15, 2003 at 17:05
John,
The rating on the tow bar is related to your
suspension capacity not the pull rating, I have done several
driver training cources all certified & they all recomend the haymen reese pin for a recovery point.Regards Bob
Where to next
FollowupID:
257877
Follow Up By: Member - Ross - Monday, Dec 15, 2003 at 17:11
Monday, Dec 15, 2003 at 17:11
I stand by my earlier comments. With the greatest of respect for the certified courses .. using the pin is asking for trouble.
I play with these sums for a living. (B.E.)Fidei defensor
Rosco
FollowupID:
257878
Follow Up By: Outnabout David (SA) - Monday, Dec 15, 2003 at 17:26
Monday, Dec 15, 2003 at 17:26
I see what your saying but I would rather snatch from a towbar held on by several HT bolts than by a rated hook held on with only two bolts. I think some caution always needs to be exercised. Too many gungho people out there that reverse up to a vehicle and have 10 meteres of slack and then floor it. I prefer a little bit of slack and if not successfull then increase and try again. The key is to keep everything to a minimum and that will increase your safety.We have so little time to enjoy our land
FollowupID:
257882
Follow Up By: Member - Ross - Monday, Dec 15, 2003 at 17:53
Monday, Dec 15, 2003 at 17:53
David
I agree with your comments entirely, particularly about not going at it like a bull at a
gate. Yes there's an overabundance of dickwits out there.
My point relates to using an oversize shackle through the toe ball hole as against linking directly to the pin with the draw bar removed. That's the part that's a no no as far as I'm concerned.Fidei defensor
Rosco
FollowupID:
257885
Follow Up By: John - Monday, Dec 15, 2003 at 18:30
Monday, Dec 15, 2003 at 18:30
BJ you may be correct in that the
suspension is one component in the Tow bars load rating, this is related to down force normally not to exceed 10% of the bars rating EG 3500 KG bar has a maximum 350 KG down force load on the bar.
Vehicle weight and mounting / chasis point is also a significant consideration as
well.
The bar is certainly not designed to cope with repeated direct rear pull's in the order of 5 plus tonnes.
My point is I know we are doing this but what potential damage is being done to the tow bar which will potentially show itself with an unexpected future failure of the bar.
At least if you damage a rated load hook you will not jepodise the tow system and it will more than likely be more easily detected by visual inspection for distorsion etc of the rated point.
I also agree with
Ross about using the pin except my reasons are for those already stated his is that the pin itself is not rated to cope.
I have said it before on this
forum, It is a real problem and the only satisfactory way to build in some sort of safety factor is to mount independent rated snatch points.
My guess is the reason people cut corners and use the tow bar is because it is easier and more to the point it cost's almost nothing.
Regards
John
FollowupID:
257888