Safety factor for spare wheel bracket

[Djinh]

I'd like to relocate the spare wheel on my 4x4 RV (an Unimog) and have to make a new bracket for it. As the spare wheel is in the order of 120 kg and we'll be driving it across rough terain shock loads will be a lot higher than on a normal car with a normal spare wheel...

What would be a reasonable safety factor to use in this case?

 

[MintJulep]

And just how high are these "a lot higher" loads?

 

[patprimmer]

A reasonable safety factor is at least double the expected maximum shock load allowing for acceptable fatigue life at that load.

Variables not mentioned are.

1) Grade of steel.
2) Shock load expected.
3) Frequency of load being applied.
4) Expected life.

Even if you provide all the data, it is to much to ask here that someone does all those sums for you.

Are there existing examples with known performance to use as a guide.

Regards
Pat
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[MikeHalloran]

Reverse-engineer the stock mount, and make the replacement stronger.


Mike Halloran
Pembroke Pines, FL, USA

 

[Djinh]

Right, that'll teach me posting late at night when I'm half falling asleep already, I was a bit unclear...

I'm not looking for anyone to do my sums. What I'm looking for is pointers to information about the kind of shock loads and frequencies that I can expect for this kind of bracket.

Further information:

- I'd prefer to use S235
- Lifetime should be for the rest of the live of the vehicle, which is pushing 44 years already now

For reverse engineering the original part I'd have to find one first. A previous owner already relocated the spare wheel and replaced the original bracket with storage space.

Alex

 

[GregLocock]

If it is mounted on the sprung mass of the vehicle then it won't see much more than a passenger does, ie 1g or so. A reasonable safety factor would be 10, as the most likely max load is a chain link fence/tree getting caught around it. That is really you are designing for abuse loads.

You also need to decide whether going back to retrieve a spare wheel that gets ripped off the vehicle is more hassle than straightening a bent spare wheel, if you make it too strong.




Cheers

Greg Locock


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