Aluminum Rear Wheel Carrier/Bumper

Submitted: Tuesday, Dec 15, 2015 at 10:12

ThreadID: 131133 Views:3016 Replies:4 FollowUps:16

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Member - abqaiq

Anyone know of vendor or experienced fabricator [done some] of such? The steel ones are heavy and every kilogram is detrimental/ Don't see a reason aluminum would not work with steel pivot pins. Looking for a dual unit for a 78 Series Troopy.

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Reply By: Gronk - Tuesday, Dec 15, 2015 at 10:35

Tuesday, Dec 15, 2015 at 10:35

No reason why it can't be done, but I don't think anyone does do it .

Aluminium fatigue is a common problem and unless you get someone who knows how to weld it and knows the right grade to use and has also made and tested a unit, I would steer clear !

AnswerID: 593821

Reply By: Hoyks - Tuesday, Dec 15, 2015 at 18:42

Tuesday, Dec 15, 2015 at 18:42

Cracking is the main reason. Commercial grade aluminium is quite soft and can be bent reasonably easily, to get around this you would want a 6061 T62 aluminium alloy, the down side here is that once you weld it you then need to heat treat it all back to the required temper or you will have cracking in the heat affected zone around the weld. Or over engineer the hell out of it so it is less likely to crack, but then the extra weight vibrating can shake it's self to death anyway..

Then there is the issue of attaching aluminium to the steel pivot, where you will need some quality aerospace fasteners and will probably have electrolytic corrosion.

If it does crack and you are away from a major town, good luck finding a workshop that is tooled up with a TIG welder or a MIG with a teflon liner all set up for aluminium welding and has a bottle of pure argon on hand.

If weight is the issue, then 4130 chrome-molly tube, fish mouthed, gusseted and TIG welded would be a better bet.

AnswerID: 593838

Follow Up By: fisho64 - Tuesday, Dec 15, 2015 at 19:50

Tuesday, Dec 15, 2015 at 19:50

you will only get electrolytic corrosion if you put it in an electrolyte like salt water

FollowupID: 862154

Follow Up By: Hoyks - Tuesday, Dec 15, 2015 at 21:04

Tuesday, Dec 15, 2015 at 21:04

I beg to differ.
If it gets damp and gets dust on it, then you will get electrolytic corrosion.

I daily drill out corroded corrosion resistant steel fasteners from aluminium aircraft structures. They, as a general rule, don't get immersed in salt water, if they do then they don't work really well afterwards.

I'm also an aircraft welder, so I hope I have a bit of an idea what I'm on about.

FollowupID: 862161

Follow Up By: fisho64 - Tuesday, Dec 15, 2015 at 22:23

Tuesday, Dec 15, 2015 at 22:23

What you are talking about is called galvanic corrosion.
How long does it take before you need to drill out these fasteners?
If it is not many years then the aircraft industry is many many years behind the maritime industries of which I am heavily involved in.
If the corrosion would be so bad in the referred to in the post, then alloy heads on cast iron engine blocks bolted with HT steel bolts would have no lifespan at all.

All I am saying is that any corrosion from disimilar metals on a spare wheel carrier would be so negligible as to be not worth worrying about

FollowupID: 862167

Follow Up By: The Landy - Wednesday, Dec 16, 2015 at 06:18

Wednesday, Dec 16, 2015 at 06:18

I think Hoyks hits on the head by highlighting that repairs in the field if a weld is required is much easier if it is made of steel.

A consideration worth taking into account...

Good luck, Baz - The Landy

FollowupID: 862176

Follow Up By: Les - PK Ranger - Wednesday, Dec 16, 2015 at 08:40

Wednesday, Dec 16, 2015 at 08:40

Yes, I feel if aluminium was a long term commercially viable material for this, they would be getting made from them now.
Hunt around, maybe there are better high strength (thinner / lighter) steel ones on the market ?

FollowupID: 862180

Follow Up By: Member - abqaiq - Wednesday, Dec 16, 2015 at 08:53

Wednesday, Dec 16, 2015 at 08:53

Good points all guys, they close the query - Thanks

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Follow Up By: ian.g - Wednesday, Dec 16, 2015 at 11:11

Wednesday, Dec 16, 2015 at 11:11

If its such a big problem how come the large number of alloy bull bars on heavy duty road trains operating in all sorts of conditions over,and in some circumstances horrific circumstances, these are all connected to steel chassis rails and on a whole don't crack and fall apart. My observations only.

FollowupID: 862191

Follow Up By: 671 - Wednesday, Dec 16, 2015 at 11:50

Wednesday, Dec 16, 2015 at 11:50

Ian

This is only a guess but it might have something to do with the amount of material (mass) in them and the distance it is from the mounting points on the chassis.

There is not much material at the top of a dual wheel carrier but that changes considerably when a couple of wheels of around 35 kilos are attached. That is a lot of material vibrating around on the end of a long lever i.e the distance from the wheels to the car chassis.

If you were to place two wheels on the top of a aluminium bull bar, the aluminium may no longer be suitable for the job.

FollowupID: 862197

Follow Up By: ian.g - Wednesday, Dec 16, 2015 at 12:04

Wednesday, Dec 16, 2015 at 12:04

The vibrations that go through a alloy bull bar on the front of a road train travelling on corrugated roads is fairly horrendous and as you say they hang a fair distance from their fulcrum point. I have never weighed my bar however there would be very little change from 80kg or possibly more. The other point was the possibility of electrolytic corrosion, have never had to drill out bolt holes on the pivots. I quite agree that 4130 Chrome Molly would be a better proposition, however I believe structural alloy tube could be used without much fear.

FollowupID: 862200

Follow Up By: Slow one - Wednesday, Dec 16, 2015 at 12:23

Wednesday, Dec 16, 2015 at 12:23

Alloy bullbar for a road train will come in over 200 kg

FollowupID: 862203

Follow Up By: ian.g - Wednesday, Dec 16, 2015 at 12:47

Wednesday, Dec 16, 2015 at 12:47

Just went and checked Alloy King Bar "Warrego 4 post Bar" without backing plate weighs 110kg.

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Follow Up By: Slow one - Wednesday, Dec 16, 2015 at 14:26

Wednesday, Dec 16, 2015 at 14:26

Just looked up the Kings roadtain Warrego bar and it comes in at 220kg.

Warrego roadtrain bar.

FollowupID: 862208

Follow Up By: Gronk - Wednesday, Dec 16, 2015 at 16:08

Wednesday, Dec 16, 2015 at 16:08

Just went and checked Alloy King Bar "Warrego 4 post Bar" without backing plate weighs 110kg.

Would the backing plate be to add strength ??

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Follow Up By: fisho64 - Wednesday, Dec 16, 2015 at 16:28

Wednesday, Dec 16, 2015 at 16:28

Plate spreads the load of bolts

FollowupID: 862211

Follow Up By: Ron N - Wednesday, Dec 16, 2015 at 18:45

Wednesday, Dec 16, 2015 at 18:45

The steel backing plate adds strength to an alloy bull bar.
Hitting a bull at 100kmh would smear a 100% alloy bar over the front of the truck, the steel provides the necessary tensile strength to resist the impact.
To get even somewhere near the strength of steel, you need more than 3 times the thickness in aluminium - and even then, it will still bend more readily than steel.
However, having said that, there's a wide range of aluminium types available, with an also wide range of strength levels.
You can get some pretty strong aluminium alloys if you want to pay accordingly.
Naturally, aviation grade alloys possess the lightest weight for the greatest strength.

FollowupID: 862214

Follow Up By: Slow one - Wednesday, Dec 16, 2015 at 20:24

Wednesday, Dec 16, 2015 at 20:24

Spot on Ron, the train bulbar is useless without the backing plate as is any alloy bar.

FollowupID: 862217

Reply By: Steve - Wednesday, Dec 16, 2015 at 18:06

Wednesday, Dec 16, 2015 at 18:06

Have a word with David here:

http://www.warringahaluminium.net/

he's in Brookvale, Sydney and knows his stuff. He is 4x4 enthusiast himself so understands the application as well as the job side of it.

As a guide, he told me he did his own roof rack at double usual strength in aluminium, which works out at half the weight of steel. Think I remember that correctly.

AnswerID: 593875

Reply By: swampy - Wednesday, Dec 23, 2015 at 12:03

Wednesday, Dec 23, 2015 at 12:03

hi
rule of thumb ,
alluminium weighs 1/3 of steel, typically to bring the alloy up to steel strength the alloy needs to be doubled in thickness . This brings the alloy to 2/3 the weight of steel .
The above only works well with a car trailer sized project .Then u must consider fatigue and wear .
Economical is alloy wheels floor ramps guards . This saves around 150kgs . Use with light weight suspension system also.

In a project as above light weight steels would be the best option

swampy

AnswerID: 594086