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Author Topic: Assembly of rear arm  (Read 1773 times)
Morne
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« on: December 27, 2020, 05:12:15 pm »

A few weeks back I made the ¨investment¨ and purchased new rear arms from Politecnic. These are expensive, but the old ones left me with some questionmarks. Especially the one seemed fine from the outside, but moving it around one could hear tons of lose pieces falling around on the inside. And it just felt wrong to just replace one arm, so it had to be both. So the planning for the coming week is to start putting things together again. So a few questions on getting the silentblocks and the wheel bearing into the new arms:

a) Any recommendation on getting the wheelbearing in? Copper grease ok to use between bearing housing and arm? Using a hydraulic press? Or rather a threaded rod with disks?

b) Any recommendation on getting the silentblocks in? Copper grease ok to use? Using a hydraulic press? Or rather a threaded rod with disks?

c) Which orientation does the silentblock go? The outside one does not seem to have any orientation (1 on the photo). The inside one has a tab on the one side, so I assume orientation is important. Looking at Simon´s drawing, it appears that the tab has to be on the center of the car (3 on the photo). Is this correct?

Thank you
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roy4matra
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« Reply #1 on: January 01, 2021, 01:48:05 pm »

A few weeks back I made the ¨investment¨ and purchased new rear arms from Politecnic. These are expensive, but the old ones left me with some questionmarks. Especially the one seemed fine from the outside, but moving it around one could hear tons of lose pieces falling around on the inside. And it just felt wrong to just replace one arm, so it had to be both. So the planning for the coming week is to start putting things together again. So a few questions on getting the silentblocks and the wheel bearing into the new arms:

a) Any recommendation on getting the wheelbearing in? Copper grease ok to use between bearing housing and arm? Using a hydraulic press? Or rather a threaded rod with disks?


I would not use copper grease which is relatively thick, because the press fit would simply push it off anyway and it would build up at the inside shoulder and possibly stop the bearing going right up to the shoulder.  First you need to make sure the inside of the arm where the bearing fits is clean of any protective painted surface which I believe is on those arms.  Then simply use a film of thin oil on that surface to assist the bearing going in.  You need to make sure the bearing is entered squarely and then pressed in all the way to the shoulder so the circlip can be fitted.  I use a small hydraulic press, and you would need something like this to get the old ones out if you were changing a bearing on an old arm as they will need a lot of pressure to move them initially - I have seen 20 tons on the press before they begin to move!  Obviously with a new arm you won't have to remove an old bearing, but the interference fit is tight and a hydraulic press makes the job easy.


Quote
b) Any recommendation on getting the silentblocks in? Copper grease ok to use? Using a hydraulic press? Or rather a threaded rod with disks?


First you need to check and clean off any paint on the inside of the tubes and then measure the inside diameter of the tubes accurately where the bushes fit, and measure the outside of the bushes also accurately to see how close a fit they are, because I have heard they may be tighter than the originals making them even harder to fit.  Again you will probably need a hydraulic press to press these metallastic bushes in to the arms as they will be a tight press fit.  You must support the arm solidly at the inner edge of the tube you are pressing the bush in to.  Obviously the bush with the flange has to go in from the outside as you could not get a press in between to push the bush in from the centre.

Roy
« Last Edit: January 01, 2021, 01:52:49 pm by roy4matra » Logged

Matraman
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« Reply #2 on: January 02, 2021, 05:32:07 pm »

I was unable to get the bushes or bearing in myself, even with a small hydraulic press. Neither could I get 10 mm threaded bar to do the job, it just stripped the thread. I cleaned out the tubes as Roy said, but the fit was just too tight for the equipment I had.

The problem with the borrowed hydraulic press I was using was that the cylinder/ram of the press was sticking up vertically above the frame, so that the opposite part of the "y" shaped trailing arm was fouling on this cylinder. There were no adapters with the press so in the end I got my neighbour to take it to his truck workshop where they pressed the bearing and bushes in easily.

I tried to get Politecnic to fit these parts before sending the arm to me, but they were unable to do it.
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Andrew
Morne
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« Reply #3 on: January 03, 2021, 07:22:31 pm »

Thank you Roy for the advice. They are all fitted now to both the arms. Next is the fitment of the hubs, once I have cleaned them up. I guess the big ¨adventure¨ will be the fitment of the arms to the car.

The driveshafts are ready, with 4 new rubber boots fitted. This after the fun of removing the metal housing which hold the boots. Then fitting new ones, and finding that they are ¨faulty¨ as the boot is lose inside the long housing. At first sight this does not seem to be an issue, but during the assembly process the boot pops-out a bit and then I don´t trust it to stay in place once operational.

In the end I did most of the fitment of the bearing and silent blocks with the kit in the below picture. To get the fitment started is tricky, as it needs to go in straight. If it is not straight, then it can turn into a whole mess and get stuck. I have a 6T press, but without a gauge. So in essence I don`t have a feel of how much pressure the press is applying. With the set below and turning by hand (no air gun) one can feel the resistance. One of the bearing´s was not straight, and I could feel it as very quickly is was not possible to turn by hand anymore. If I went in with the press, I maybe would have destroyed the bearing. That said, it does take quite a bit of elbow grease to do this by hand Grin.

I used the M12 rod in the kit. Matraman I guess the M10 was just not enough. That said, did you use a kit like this, as each rod is fitted with bearings on each side. If you use a normal rod and washers this will not slip as easy and just add more resistance.
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roy4matra
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« Reply #4 on: January 03, 2021, 08:36:44 pm »

Thank you Roy for the advice. They are all fitted now to both the arms. Next is the fitment of the hubs, once I have cleaned them up. I guess the big ¨adventure¨ will be the fitment of the arms to the car.

A couple of things here Morne.

First, if you have new bolts for the arms to the chassis make sure they are NOT stainless steel bolts, as they are not hard enough.  They must be steel grade 8.8 minimum and stainless bolts this size are not up to that, so when you tighten them, they will stretch and the arm comes loose and will move around and you will have rear end steering!

Second, because these bolts are not stainless, they can corrode in to the bushes and if you need to take them out at any time to remove the arms, they make be impossible to get out again.  So you need to grease them well.

The easiest way to do this is whilst the arms are off the car.  Put some LM grease into the bushes and coat the bolts a little too, then slowly push the bolt into the tube from one end whilst rotating it back and forth and holding a finger lightly over the hole the other end, so air can escape but the grease will get forced between the tube and bolt, and coat the inside of the tube.  Do this from both ends in turn, to make sure they are well covered.  Now when you fit the arm into the chassis and insert the bolts, use a little more grease and again have your finger light on the other end.  This action will make sure it is nicely greased.

The problem is that if you simply put some grease on the bolt and push it in, most of the grease will get taken off at the edge of insertion, leave much of the inside of the tube without grease and it can still become seized over time with corrosion.

Roy
« Last Edit: January 03, 2021, 08:40:05 pm by roy4matra » Logged

maxderoswell
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« Reply #5 on: January 09, 2021, 09:34:27 am »

Hello everybody.

Happy New year.

From your mind, do you it's possible that powerflex in UK can produce element for the murena.

I think it's no but it can be better than original mounting.

Mathieu
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roy4matra
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« Reply #6 on: January 09, 2021, 12:43:16 pm »

Hello everybody.

Happy New year.

From your mind, do you it's possible that powerflex in UK can produce element for the murena.

I think it's no but it can be better than original mounting.

Mathieu

Hello Mathieu,

I would seriously advise against changing the suspension bushes for poly urethane ones, even if you can get them the right size and shape (which is doubtful).  A manufacturer spends a lot of time getting these just right to give both great handling and ride comfort.  Changing them, especially only at the rear on the semi-trailing arms, would upset the delicate balance and probably make the car worse and uncomfortable and probably more noisy.

If you do a search of this forum, (select Murena only, and search 'poly bush') you will find older postings where some have tried and found to their cost that it makes the car worse, and they will also advise against it.

So unless you intend to race the car and need the firm suspension, and don't care about normal road behaviour, then stick with the originals.

Roy
« Last Edit: January 09, 2021, 12:47:02 pm by roy4matra » Logged

Morne
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« Reply #7 on: February 13, 2021, 04:24:56 pm »

At last I got some time to continue to prepare for the re-assembly of the arms.

While the drive shafts are out, I thought I would replace the oil seal around the drive shaft where it goes into the diff. At first I thought I would just replace the oil seal while leaving the housing in place. This is easier said than done, and in the end I decided to remove the cap which hold the oil seal. This means I also replace the o-ring between the cap and the diff housing.

All good, got it out and replaced the oil seal and the o-ring. While making sure that the oil seal is sitting at the 3mm depth as indicated in the workshop manual. Starting assembly I am puzzled as to the orientation of the spacer below the cap. As per the photo, there is a gap in the spacer. Does this gap have to be at a paticular location?
Looking at Simon`s drawings, it appears to be at a 9 o`clock position.

Does this orientation matter, or not?
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roy4matra
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« Reply #8 on: February 16, 2021, 07:03:33 pm »

At last I got some time to continue to prepare for the re-assembly of the arms.

While the drive shafts are out, I thought I would replace the oil seal around the drive shaft where it goes into the diff. At first I thought I would just replace the oil seal while leaving the housing in place. This is easier said than done, and in the end I decided to remove the cap which hold the oil seal. This means I also replace the o-ring between the cap and the diff housing.

All good, got it out and replaced the oil seal and the o-ring. While making sure that the oil seal is sitting at the 3mm depth as indicated in the workshop manual. Starting assembly I am puzzled as to the orientation of the spacer below the cap. As per the photo, there is a gap in the spacer. Does this gap have to be at a particular location?
Looking at Simon`s drawings, it appears to be at a 9 o`clock position.

Does this orientation matter, or not?

First that ring is an adjustment shim, not just a spacer, and there were 29 of them available originally in steps of 0.05mm from 4.25 to 5.65mm.  The Matra parts slide shows the gap at the 9 o'clock position, but I'm not sure it is that relevant as there is no mention in the workshop manual.  Be careful of Simon Auto's parts drawings as things are not always in the correct relationship to one another.  They are purely made to show the parts.  They also do not include all the parts on the Matra parts fiche, as they contain mostly what they have available.

Roy
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Morne
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« Reply #9 on: February 21, 2021, 09:07:22 pm »

Thank you Roy for all the information.

I ordered the bolts for the arms new from Simon, so I would expect that they are correct. I checked the heads, and they are all 10.9 spec.

The arms are now completely built up and ready for installation. Yesterday I was also cleaning the mounting points, and next week I will give it a lick of paint to protect any exposed areas. I am excited to get the car back on its wheels again as it has been on the jacks stand for quite some time.
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GP
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« Reply #10 on: March 05, 2021, 11:05:49 pm »

Hi, I have been following the thread with interest. You have your new rear arm bolts now which is fine.

Something of engineering interest (I hope?) though below regarding some special Bumax 88 stainless steel bolts for you and the viewers....

https://www.accu.co.uk/en/hexagon-bolts/276071-SEB-M18-120-BUMAX88

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

Readily available in lots of sizes including nuts and washers. They are even stronger than a 12.9 bolt!

Question: What are the sizes of the 4 x bolts used in a Murena rear arm please, so I can do some research and costings myself?

Thanks, Graham

« Last Edit: March 06, 2021, 11:15:25 am by GP » Logged
roy4matra
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« Reply #11 on: March 08, 2021, 09:29:10 am »

Hi, I have been following the thread with interest. You have your new rear arm bolts now which is fine.

Something of engineering interest (I hope?) though below regarding some special Bumax 88 stainless steel bolts for you and the viewers....

https://www.accu.co.uk/en/hexagon-bolts/276071-SEB-M18-120-BUMAX88

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

Readily available in lots of sizes including nuts and washers. They are even stronger than a 12.9 bolt!

Question: What are the sizes of the 4 x bolts used in a Murena rear arm please, so I can do some research and costings myself?

Thanks, Graham


Hello Graham, it is interesting to hear of some stainless steel bolts stronger than the normal ones.  I wonder if they have these sizes available and what is the cost?

The rear semi-trailing arms use two bolts to the chassis, one M12 x 1.75 x 90mm and one M12 x 1.75 x 110mm, the longer one to the centre.  So you would need two of each.  There is a shorter one to connect to the bottom of the strut which is an M12 x 1.75 x 70mm and although this one is not normally a problem, it might be nice to have all three the same, if available.  You need a washer on each plus an M12 x 1.75mm Nyloc nut.

Roy
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GP
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« Reply #12 on: March 08, 2021, 03:06:50 pm »

Hi Roy,

Pleased and suspected you would have found it of  interest.

Thanks for the information on bolt sizes.

I will do some research now and hopefully come up with a supplier and price for future reference.

Keep you posted......

All the best and take care, (Everyone else too!)

Graham
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GP
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« Reply #13 on: March 14, 2021, 07:59:30 am »

I have looked into this further and the bolts in this sizes required do not quite reach Class 10.9 Quenched and Tempered Alloy Steel Strength of Min. Tensile Strength (MPa) 1040 / Yield Stength (MPa) 940. Although BUMAX 109 is close enough (1000/900). But only available in the 90mm and 70mm length. It is available in 120mm length to order though, which could probably be shortened to suit in the order?

The locking nuts are only BUMAX 88, so a plain nut in BUMAX 109 would have to be used with Loctite or say a spring washer in addition to the plain washer required.

ACCU regardless is a good go-to site for most kind of bolts and provide a top class service.

F.Y.I. See attachment's below of BUMAX Technical Strength's:

https://www.bumax-fasteners.com/properties/mechanical-strength/

The actual bolts in question with prices per 1 x item:

https://www.accu.co.uk/en/hexagon-bolts/276174-SEB-M12-90-BUMAX109    £8.98 / each.

https://www.accu.co.uk/en/hexagon-bolts/276037-SEB-M12-110-BUMAX88    £9.04 / each.

https://www.accu.co.uk/en/hexagon-bolts/276176-SEB-M12-120-BUMAX109   Special Order Get a Quote.....

https://www.accu.co.uk/en/hexagon-bolts/276172-SEB-M12-70-BUMAX109     £8.23 / each.

Locking nuts:

https://www.accu.co.uk/en/bumax-flanged-locking-nuts/396353-HBFL-M12-BUMAX88   Special Order Get a Quote.....

https://www.accu.co.uk/en/bumax-collar-locking-nuts/396395-HBCL-M12-BUMAX88     Special Order Get a Quote.....

Plain nuts:

https://www.accu.co.uk/en/bumax-hexagon-nuts/269022-HPN-M10-BUMAX109      £2.61 / each.

Washers:

https://www.accu.co.uk/en/bumax-metric-flat-washers/268154-HPW-M12-BUMAX109    £2.02 / each.

https://www.accu.co.uk/en/flat-washers/63162-HDTW-M12-A2    £0.73 / each.

https://www.accu.co.uk/en/rectangular-profile-spring-washers/62550-HRSW-M12-A4    £0.21 / each.

NB: Prices are discounted with greater quantities. However they add Shipping and Tax to the order.

Probably around £100:00 for a complete set for a Murena!  Undecided

« Last Edit: March 15, 2021, 08:35:23 pm by GP » Logged
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