CVRT lean

[TooTallMike]

As the CVRT people may recall, our Spartan MCT had developed a lean to the left front over the past year.

 

With the tank standing on our trailer, Grasshopper today measured the distances from the bottom of the sponson to the hub centres:

 

Right hand side: all 575mm

 

Left hand side from front: 535mm, 545mm, 555mm, 565mm & 565mm

 

Could someone tell us if this indicates a broken or weak torsion bar or if there's something else going on?

 

We've tried levering the front ones up and they don't appear any different to the others.

[Tony B]

go on a diet mate? Or change the heavy weight to the other side? Stick with wheels at least you can shove a bit of wood in the springs. :-D

[sirhc]

Mike,

 

It does seem like you've got a problem with the left hand side torsion bars. What does the rubber on the roadwheels on these 4 wheel stations look like? There should be a bulge where it's in contact with the road. If there is no bulge it suggest broken or weak torsion bars.

 

Chris

[TooTallMike]

Are the torsion bars known for getting weak or breaking? If weak, can we just turn it round a spline? We do have a spare...

 

We'll look at the rubber when it's not raining :roll:

[TooTallMike]

Also, is there an EMER for setting them up?

[sirhc]

Mike,

 

I have AESP 2350-T-220-522 which has a chapter on setting up the torsion bars. I'll try and scan the relevant pages for you. I guess they must have problems with them as there's quite a bit of information about them in the manual.

 

Chris

[TooTallMike]

Thanks Chris,

 

We just browsed the AFV site as well and there's a chap who thinks he has weak torsion bars but there's not much indication as to what he plans to do about it. Looking at the parts book plate J6, there is a retaining pin item 13 which appears to be the only thing holding each entire torsion bar and suspension arm assembly to the vehicle, but we can't see how to get to these pins. Any ideas? We've not had to go this far into one of these before :dunno:

 

It may be obvious when we look at the vehicle but we're hiding from the rain at the moment and trying to work it out from the dwgs...

 

Cheers - Mike

[Tony B]

On a serious note Mike. My experience with torsion bars is they go or they dont. The diffrences are quite minor. How are the bars supported as they enter the hull? Could you have a worn bushing ? I did hear talk of similar problems caused by the floor plate buckling under heavy use.

[TooTallMike]

On a serious note Mike. My experience with torsion bars is they go or they dont. The diffrences are quite minor. How are the bars supported as they enter the hull? Could you have a worn bushing ? I did hear talk of similar problems caused by the floor plate buckling under heavy use.

 

Hi Tony,

 

The torsion bars are similar to halfshafts in a tubular axle: There is a tubular stub which is mounted on a plate which in turn is bolted to the hull. The swinging suspension arm has a plain internal bushing and rotates around the outside of this stub with a small oil hole for lubrication and a lip seal at the rear. The torsion bar passes through the stub and has splines which locate it in the back of the mounting plate for the corresponding suspension unit on the opposite side of the hull. On the outer end of the torsion bar is a flange which is bolted to the outside of the suspension arm. All that appears to hold this lot onto the vehicle is a small pin (the item 13 I referred to) which appears to be inserted through the side of the female splined recess on the back of the mounting plate (ie. inside the hull :dunno:) to match up with a machined slot in the splined section of the torsion bar. We can't see how to get to this to release it.

 

I bet that doesn't make any sense :-D.

 

- Mike

[TooTallMike]

Subsequent to that, Chris has just very kindly sent us some info. :thankyou: which says there is an access hole under each plate to insert a puller to get the pins out.

 

Easy peasy I'm sure... :argh:

[Tony B]

Mike it is late '70s British Military design, who said it had to make sense? Surley there has to be a way to re twist the torsion bar whilst it is in place? Even the French have a system for doing this.

[gwrco]

mike,

.....i spoke to one of our R.D.G PSI's at Dunmore Park TA centre yesterday, and he said it is more than likely to be a badly damaged/broken torsion bar.

If it is a normal road wheel (not the drive wheels), and you can actually lift the road wheel up from the track then the torsion bar inside it is broke. The way around this is to replace it, but first you will have to remove the road wheels from both sides, remove the arms, and you will find this a lot easier to do the work. Remove all the shearings, dirt, etc, inside then fit a new torsion bar in!

 

hope this helps,

 

tim

 

[TooTallMike]

mike,

.....i spoke to one of our R.D.G PSI's at Dunmore Park TA centre yesterday, and he said it is more than likely to be a badly damaged/broken torsion bar.

If it is a normal road wheel (not the drive wheels), and you can actually lift the road wheel up from the track then the torsion bar inside it is broke. The way around this is to replace it, but first you will have to remove the road wheels from both sides, remove the arms, and you will find this a lot easier to do the work. Remove all the shearings, dirt, etc, inside then fit a new torsion bar in!

 

hope this helps,

 

tim

 

 

Hi Tim,

 

Thank you very much for that. We can't lift any of the road wheels up but we've heard that if it's an angled break they'll still touch at the fracture surfaces and resist even though they'll be greatly weakened. We're going to have to pull the torsion bars and see what's there.

 

We'll post some pics here when we know.

 

- Mike

[abn deuce]

I ll keep my fingers crossed for you and hope that you dont have any broken ones although it sound like a L-O-T of work ahead to find out , So many parts to remove just to get started and then The Real work begains of course after all that You have to re-install all those parts road wheels , tracks, etc . Sound like a multi -month project ?

[sirhc]

It shouldn't take too long, all the jobs on a CVRT are pretty straight forward & easy. Mike and Vince were trying to set the record for a gearbox change at Beltring. I don't think it went quite to plan though?

 

Chris

[Grasshopper]

I blame the constant interuptions of other forum members! They were most welcome, and it meant lots of tea/beer breaks. We did however forget to have lunch. Wondered why I was getting so p***** off with the thing. Vince becomes disinterested when hungry. Beer made me forget I was hungry.....

 

I have now removed most of the wheels on the suspect side of the CVRT (which is at a convenient height due to living on our trailer) and none of the torsion bars seem to be broken.

 

Having measured the droop of the arms and compared them to the figures in the EMER, they all sit too high up. I suspect that they have all been installed incorrectly, but I need to remove the paint from the outer flanges to check the markings. This vehicle had been stripped for spares at Batus, so they may have all been removed then re-fitted just to move it back to the UK. Pictures to follow.

[Grasshopper]

Pics as promised. I have measured the droop of all the suspension arms, and the second one hangs at 25 inches, when it should be 27 inches from the sponson to the hub centre. If it were broken, it should hang lower. All the others sit an inch or so too high. With all wheels lifted, none of them wobble excessively to indicate a broken torsion bar. I am hoping that it has just been fitted incorrectly.