FAT Radius arm

[SIM79]

Found this on the Patrol forum

[QUOTE=Induro;324807]Well i dropped this pic in another post, a few coments so i thought i would start a new thread.



This has taken me about 6 years to put into production. why?
well,
i've laminated arms, they broke.
i've made the dropped standard replacement laser cut arm out of mild and high tensile steel, they broke
i have made them simillar to the 3rd's style using a ChroMo spherical bearing, they broke

i've been playing with this design for a few years trying to get it right and this is the about the 10th time round and they haven't broken.

The round stuff is hollow bar with an 10mm wall, the web is 10mm mid steel (needs to twist)

the drop down is to allow more twist in the arm instead of relying on bushes, and in regard to flex pretty much every body who has used them has put back on there sway bars.

the standard arm is for a 4" lift althouogh we can change this to suit any lift from 3" up probably 10" (if you were that silly), they have a drop box which is basically the same as the one i have been doing for ages.

The Tie rod runs through the gap in the web[/QUOTE]

[KiwiBacon]

Part of your axle articulation comes from flex in the radius arms themselves.
He's just removed all of that.

[bogged]

Part of your axle articulation comes from flex in the radius arms themselves.
He's just removed all of that.

Flex is very overrated.

[SIM79]

[QUOTE=Induro;324856]the easyest thing i guess is follow the link

http://s150.photobucket.com/albums/s103 ... ius%20arm/

a set of arms and drop boxes are $1990[/QUOTE]

[nastytroll]

I have seen ladder arms done before and thay had cracking problems as the to rods will try and act as a 5 link and flex through the web. Eventually it will fracture.

This is a better design, pic borrowed from another forum.







The extra joint removes the bind out of the arm.

[bj on roids]

Just run a stock 80 series arm?

[1MadEngineer]

This has taken me about 6 years to put into production. why?
well,
i've laminated arms, they broke.
i've made the dropped standard replacement laser cut arm out of mild and high tensile steel, they broke
i have made them simillar to the 3rd's style using a ChroMo spherical bearing, they broke

i've been playing with this design for a few years trying to get it right and this is the about the 10th time round and they haven't broken.

The round stuff is hollow bar with an 10mm wall, the web is 10mm mid steel (needs to twist)

the drop down is to allow more twist in the arm instead of relying on bushes, and in regard to flex pretty much every body who has used them has put back on there sway bars.

the standard arm is for a 4" lift althouogh we can change this to suit any lift from 3" up probably 10" (if you were that silly), they have a drop box which is basically the same as the one i have been doing for ages.

The Tie rod runs through the gap in the web

sorry BUT is this guy for real? they are some VERY interesting statements to say the least!
who would admit to laminating stock arms? the cast steel has way too high a sulphur content and this is never going to give you a successful weldment. And as for stating that the arm NEEDS to flex! ------ fatigue seems to spring to mind.

apart from that it does look like a nice cheap effecient way of manufacturing.

[Fathillbilly]

This has taken me about 6 years to put into production. why?
well,
i've laminated arms, they broke.
i've made the dropped standard replacement laser cut arm out of mild and high tensile steel, they broke
i have made them simillar to the 3rd's style using a ChroMo spherical bearing, they broke

i've been playing with this design for a few years trying to get it right and this is the about the 10th time round and they haven't broken.

The round stuff is hollow bar with an 10mm wall, the web is 10mm mid steel (needs to twist)

the drop down is to allow more twist in the arm instead of relying on bushes, and in regard to flex pretty much every body who has used them has put back on there sway bars.

the standard arm is for a 4" lift althouogh we can change this to suit any lift from 3" up probably 10" (if you were that silly), they have a drop box which is basically the same as the one i have been doing for ages.

The Tie rod runs through the gap in the web

sorry BUT is this guy for real? they are some VERY interesting statements to say the least!
who would admit to laminating stock arms? the cast steel has way too high a sulphur content and this is never going to give you a successful weldment. And as for stating that the arm NEEDS to flex! ------ fatigue seems to spring to mind.

apart from that it does look like a nice cheap effecient way of manufacturing.

maybe you should have a look under a few patrols that have done the OBC

[1MadEngineer]

maybe you should have a look under a few patrols that have done the OBC

yep and some still run stock nissan arms? so does that make them equally as goodl?

[ludacris]

Very nice design. They look tops .

Cris

[chpd80]

From his reputation, I would be very surprised if F.A.T. put his name and
reputation on anything sub-standard.

[Z()LTAN]

they use stocko arms because they are strong enough and light.

They are also small and cheap so you can carry many spares.

imho

[morewheeldrive]

I would love to see how these arms perform. Maybe a you tube clip with a comparrison between other leading brands. I understand the concept and I think as far as fatigue goes I'd say the rubber bushes would take most of the breaking strain and would wear out before the webbing cracks. I love F.A.T's designes. Only wish I could afford to own some.

[SLASH]

They look good & i like the idea of them. Any close up pics of them with drop boxes fitted to a truck? Cheers Loz.

[SIM79]

Contact FAT for more pics.

[Auto-Craft]

[quote="SIM79"]Contact FAT for more pics.




They broke at the OBC.

The other link of the laminated arms is certainly the mosy popular design for more strength in desert racers.

We bring some gear from these guys, and build type and quality is always extremely good.

[SLASH]

If they are breaking, where abouts are they breaking from?

[SuperiorEngineering]

That is a huge amount of ground clearance lost for no real benefit.

Their is no possible way these would be stronger than a properly manufactured radius arm, that is a very unrealistic claim to make.

That claim should be backed up with real tests and a stress analysis not a guess.

[nottie]

All this to try and make a patrol front end flex

[flexytj]

why not just convert to 5 link if flex is the issue ?

[eliteforce32]

or talk to the man one post above yours about front arms ^^^^

[KiwiBacon]

That is a huge amount of ground clearance lost for no real benefit.

Their is no possible way these would be stronger than a properly manufactured radius arm, that is a very unrealistic claim to make.

That claim should be backed up with real tests and a stress analysis not a guess.

My thoughts too.
Radius arms need to flex and are made to flex. If you try to make them rigid (like the above arms) you're increasing the loads on everything including the arms.
Result, something breaks.
So you strengthen that and see what breaks next.
Eventually everything is strong enough and you've gained 100kg+ of metal for what benefit?

[Z()LTAN]

I dont know about the whole "radius arms are designed to flex within themselves" theory... I dont think 40mm thick steel is ever designed to flex around under only a passenger car.

I do agree that these F.A.T arms do look gimmicky and you do loose allot of clearance (something you nissan boys need all you can get of)

Also, you guys know that those arms shown cannot work on a standard patrol front end? U need custom parallel drop boxes for them... These look more suited to a bolt on for a Toyota 3link

[KiwiBacon]

I dont know about the whole "radius arms are designed to flex within themselves" theory... I dont think 40mm thick steel is ever designed to flex around under only a passenger car.

Everything flexes. The only difference is how much.

I happen to have a solidworks model of a rangerover radius arm. I just ran a FEA simulation on it. They flex about 3mm for every 100kg force at the end.

[bj on roids]

A bit off topic, but, I love the way they did the snorkel on that red patrol. Looks great.

[Auto-Craft]

If they are breaking, where abouts are they breaking from?

The ones I saw

[Fathillbilly]

Yes, during the OBC Jeff Redman and Jason broke one. according to them they hit a washout at over 80Km/h and picked up the whole rear of the car and almost flipped it, they got out had a look couldn't see anything broken and finished the stage, half way through the next stage the arm broke where Darren kindly pointed out. They stuck a socket up the centre welded it back together and finished the event.

If you have a look one the patrol forum you will see that I have already pointed this out
http://www.patrol4x4.com/forum/showthread.php?t=40226

but as that post points out, and as I always have and always will, I’ve gone back and changed things to address the issues, I changed the web lay out to finish at he bush instead of along that area of CDS and have up graded from a 6mm wall CDS to a 10mm wall CHB and I’ve increased the web from 8mm to 10mm

If you are having trouble getting through/over something because of loss of clearance you mustn't be going fast enough

Thanks for the input, as always Outerlimits provides an endless supply of wisdom and knowledge.

[Auto-Craft]

I did note the new arms were gussetted differently, as per the original pic.

[hotrod4x4]

So straight from your reply, they are only suited to high speed events.
Which is also when you don't need as much articulation.

[SuperiorEngineering]

I would love to see a finite element analysis to show us how these arms are stronger than a "properly" manufactured radius arm ?