Securing Rolled Over Axles on a Tandem Van.... potential for cracked springs

Submitted: Monday, Feb 01, 2010 at 10:02
ThreadID: 75659 Views:4765 Replies:5 FollowUps:4
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Friend has a Tandem Van and wanted to increase the off road height. Rolled over the axles did all the required things now the springs are on top of the axles.

As you know with the springs underneath the axle, there is a plate and pin to centre the springs or such like, the U bolts go over the axle and springs to bolt to a plate underneath both the axle and springs.

I understand that the standard way of attaching the springs above the axle is to weld the centring pin/plate on top of the axle and put the plate on top of the springs (springs on top of the axle)with the U bolts being upside down. with this method I see a higher potential for breaking the top Spring.

Under axle setup: With the spring leafs fixed between the axle and the botton plate, large movement of the springs upward would put some pressure on the spring where it comes in contact with the 50mmx50mm axle/centreing plate. ie the pressure point on the spring is approx25mm from the axle centre.

With the 120mm x 80mm plate ontop of the axle, the pressure point on the spring is 60mm away from the centre and with movement of the spring there is a greater chance for it to break .ie less movement of the spring to apply the same shearing pressure

Of course this is all my theory which could be completely wrong,(and I am not a mechanical engineer) and thousands of vanners have rolled their Springs without problems.

I have seen the results of top broken springs on tandem vans, but both with springs under the axle, and with a ratio of 1000 to 1 or more(Under to Over) of course its the more likey outcome.

Comments appreciated.

Peter
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Reply By: Member - ross m (WA) - Monday, Feb 01, 2010 at 10:23

Monday, Feb 01, 2010 at 10:23
My trailer was sold new with SOA (spring over axle).

The plate on top has a locating pin which goes through the leaf and the u bolts hold it to the axle.
I cant see the need for welding pins to the axle
AnswerID: 402044

Follow Up By: PeterInSa - Monday, Feb 01, 2010 at 10:27

Monday, Feb 01, 2010 at 10:27
I think the plate with the locating pin is welded to the axle, but could be wrong. My point is are under axle spring leafs less likely to break than over axle Springs ie the top leaf.

Peter
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Reply By: Member - Roachie (SA) - Monday, Feb 01, 2010 at 10:25

Monday, Feb 01, 2010 at 10:25
Peter,
Whilst I see your point, I believe the amount of "flex" in the top spring over the additional 60mm distance from the centre would be so negligible as to be barely worth considering.....
I wouldn't be too concerned at all. Even if he does break a top spring, you/he will never know whether it was caused by the act of doing the "spring-over" conversion (or "rollover" as you call it), or whether the spring was going to break anyway....no way of knowing.

Cheers

Roachie
AnswerID: 402045

Reply By: Member - Malcolm (Townsville) - Monday, Feb 01, 2010 at 10:57

Monday, Feb 01, 2010 at 10:57
Peter

I have done this to my tri-axle gooseneck trailer.

From my experience you do not have to weld anything to the axle.

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AnswerID: 402050

Follow Up By: kev.h - Monday, Feb 01, 2010 at 18:31

Monday, Feb 01, 2010 at 18:31
Malcolm
Round axles have a small plate welded to the axle to stop the axle pivoting and working loose it fits over the head of the spring centre bolt and also stops the axle applying a point load to the spring
For your square axle i think you are right that there is no need to weld anything
Cheers Kev
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FollowupID: 671574

Follow Up By: PeterInSa - Monday, Feb 01, 2010 at 18:51

Monday, Feb 01, 2010 at 18:51
Malcom,
Noticed you double Nutted your U bolts, I take it the nuts are standard nuts not the Nuts with the Plastic Grip/steels ones(cannot think of the correct name).

Our van had only one nut(with the plastic insert) and I found that they worked loose after a while then double nutted the U Bolts.

Peter
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FollowupID: 671581

Follow Up By: Member - MUZBRY(Vic) - Monday, Feb 01, 2010 at 19:28

Monday, Feb 01, 2010 at 19:28
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Reply By: Member - Tour Boy ( Bundy QLD) - Monday, Feb 01, 2010 at 19:44

Monday, Feb 01, 2010 at 19:44
I always have my trailers built that way (SOA) and I've never had an issue.

Just a point to note, all 4wd factory dual cab utes have SOA rear ends as standard as do most single rear axle leaf sprung trucks.

My 4wd coasters are all to be fitted the same way.

Cheers
Dave
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AnswerID: 402145

Reply By: snapper49 - Monday, Feb 01, 2010 at 22:02

Monday, Feb 01, 2010 at 22:02
Nyloc nuts are what you were thinking of and yes double nutting is a much safer way of doing up U Bolts
SOA is also much safer as it takes all of the weight off of the U bolts which then only act to keep everything in place
AnswerID: 402171

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