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RV-Dreams.com Home -> RV-Dreams Community Forum -> RV Maintenance and Technical Tips -> Slide Bolts Breaking
Post Info TOPIC: Slide Bolts Breaking
Neil and Connie


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Slide Bolts Breaking
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Hi…wanted to see if I can do a quick survey to see if anybody else is having a similar problem to Connie and I as well as Bill and Linda Napier.

We've both got News Horizons 5vers…but the issue is with Lippert slide mechanisms. On our LR slide…which is what NH calls a Super Slide as it's about 35-40 inches deep and lifts up before it comes in so it fits flush with the floor when extended. On our rigs we've had multiple failures of the bolt in the front to rear connecting rod. As you're probably aware the hydraulics pushes the front of the slide in and out and there is a rack and pinion at each end of the slide. There's a hollow transfer shaft that connects the two pinion gears so that when the front of the slide moves it turns it's associated pinion then the torque is transmitted to the rear and the rear rack and pinion pushes the rear of the slide in and out.

We've had both the front and rear bolts break…although more fronts than rears. They're the proper bolt (at least other NHs have identical grade 8, 1/4x20 bolts. The bolts essentially serve as shear pins.

Bill and I…well at least our current theory…is that the bolt is simply under designed for the depth and length of the super slide and that there's nothing to really be done about it except have some spares in our kit. Neither of our slides seems misaligned and they're not binding going in or out…and we are both careful to extend/retract the slides before we fully level so as to make sure that the frame isn't twisted…this is in line with NH's shop guys recommendation to have front jacks down but just enough to take the weight and not twist the frame anyway with the wheels all still bearing the weight.

Anyway…anybody else with Lippert mechanism super slides having these sorts of problems. I would think it would be a systemic issue with any long/deep Lippert hydraulic slide mechanisms…but with our best engineering analysis coming up short who knows if there might be another problem.

Thanks.



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dianneandsteve


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We've had the exact same thing happen twice on our 09 Montana which also has the Lippert system. Luckily we just happened to be at a Camping World for another issue when this happened the first time. The tech allowed me to watch as he fixed it which was lucky for me because the next year it happened again and we were 60 miles from civilization. It's always the bolt in the front of our longest slide, so now I carry spares and replace it yearly before another breakage.

 



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Bill Murray


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While I have not experienced this issue (yet) I did go out and buy 4 bolts today so when it does happen I will be prepared, so thanks for the heads up. Looking at my bolts it seems possible that the reversing action may continually "pinch" the bolt and perhaps after "X" cycles it may start to fatigue and cut into the bolt. Just a theory. Have you noticed any evidence of "cutting" on the broken bolts?

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Bill Murray


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While I have not experienced this issue (yet) I did go out and buy 4 bolts today so when it does happen I will be prepared, so thanks for the heads up. Looking at my bolts it seems possible that the reversing action may continually "pinch" the bolt and perhaps after "X" cycles it may start to fatigue and cut into the bolt. Just a theory. Have you noticed any evidence of "cutting" on the broken bolts?

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Bobc


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How long are these bolts

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Neil and Connie


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Bobc wrote:

How long are these bolts

 Thanks all…looks like a couple of answers that match up with our idea that it's just under designed for the large slide.

It doesn't look like a fatigue problem…the bolts just fracture. My personal guess…as a recovering mechanical engineer…is that because grade 8 bolts are stronger but more brittle than grade 5's they are breaking due to impact. All of mine (save 1) that broke were noticed on trying to extend slides after a transit day…in each case had some significant bumps on the road that day due to bridge/highway joints that weren't very smooth. In each case it was pretty apparent to me that the bolt was already broken when we went to extend and not broken by the start of extension as the other end of the slide never moves which tells me it was broken already.

I've started to make sure that when pulling the slide in we stop as soon as it seats against the seal and not to put any extra hydraulic pressure on it…which would translate to more stress in the bolt due to torsion stress in the transfer shaft…which would translate to easier to break on the shock of the impact. We also started to give the large slide about a half second bump in the outward direction after it seats on retraction of the slide…not enough to actually allow the slide to move but just to relieve the pressure in the operating mechanism and hence hopefully lower the likelihood of failure. We've only moved twice since then though…so it's hard to say if that will make any difference.

Bob asked for the bolt size…they're grade 8 1/4x20. IIRC they're either 1.25 or 1.5 inches long but I'll measure one tomorrow and let you know. Just make sure to buy grade 8 spares and to get grade 8 nuts to go along with them. You can tell the difference between them because grade 5's only have 3 of the lines on the head and grade 8's have 6. You can see the difference at 

https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx

 --added later

OK, measured my spares and they're 1.5 inches long. Make sure you but grade 8 fasteners as well…when I get them I get both regular and locknuts as well as 1 lock and 2 flat washers per set…the last ones I got by weight at Tractor Supply and paid something like $1.25 for 4 sets. I put a flat washer on the head end and thread end and either a lock washer/nut combo or a self locking locknut. They just serve as shear pins to rotate the shaft that transfers torque back to the rear.

 



-- Edited by Neil and Connie on Wednesday 4th of May 2016 10:27:27 AM

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MarkS


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Lippert? Under Designed? You can't possibly be serious! 💩💩💩

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BiggarView


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MarkS wrote:

Lippert? Under Designed? You can't possibly be serious! 💩💩💩

 I was wondering how long it would take for you to express your well-known (on this forum, anyway) fervent and endearing "support" for Lippert.  biggrinwink



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MarkS


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BiggarView wrote:
MarkS wrote:

Lippert? Under Designed? You can't possibly be serious! 💩💩💩

 I was wondering how long it would take for you to express your well-known (on this forum, anyway) fervent and endearing "support" for Lippert.  biggrinwink

I was biting my tongue. But honestly, there is absolutely no excuse for the bearing failures and tire failures we see in RVs. There should "never" be a failure of a properly maintained system. The never is in quotes because it really means infrequently or neverish. 



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Bill and Linda


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MarkS wrote:

I was biting my tongue. But honestly, there is absolutely no excuse for the bearing failures and tire failures we see in RVs. There should "never" be a failure of a properly maintained system. The never is in quotes because it really means infrequently or neverish. 

Mark, I so, so agree with you.  But you and I are - strike that "are" replace with - "were" - used to professional equipment.  Nuff said.



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