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Post by enigmas on Jun 22, 2015 11:41:04 GMT
Good work Steve...love the deduction! We finally agree on something Richard...the repro ball joint boots are garbage! I've replaced 3 sets over a relatively short span of time. As my car was a daily driver they were lucky to last 2 years and currently once again require replacement.
Moving on. It's one thing to calculate movement of the bushes in situ with static load on or off the bush (i.e., in extension.) It's quite another when there are dynamic forces at play...which are none too subtle when the car is in motion. Cresting a hill, braking suddenly, encountering road irregularities, pot holes and corrugations impose forces much greater. Both the car's mass and inertia at speed can well stress the limits of the mounts elastic deformation. But if driven quietly and sedately it's not an issue for the traditionalist restorer who is content with the quality of the ride.
Bissmire that's an interesting lower steering column support. I imagine it would work effectively if you've fitted the solid mounts to the subframe (ensuring that subframe movement is negligible to nil) otherwise there'd probably be a shearing load imposed between the steering column where it attaches to the power steering box at the coupling point. I have no personal bias one way or the other over the additional support, but believe it may not be necessary if the subframe is bolted rigidly to the body as the two units should ideally now work as one. So there should be no independent movement of one in opposition to the other. If you've fitted the solid mounts the addition of the lower steering column support certainly won't hurt anything.
Bissmire If you've driven the car with the solid mounts fitted, could you provide some feedback/general observations as to how both the suspension and body handle the change, as I'm sure there's interest in this modification from both a technical and traditionalist viewpoint.
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Post by Warwick on Jun 22, 2015 12:15:06 GMT
Just for information. From delving in some dusty old workshop manuals I've found the contrasonic bush was not (as I thought) confined to the rover. Leaving aside similar rubber bushes on subframes used by all sorts of makers in the past ,the contrasonic rubber bush was used on some very heavy commercial vehicles in the late 40s early 50s. ... Even later than that Kev. I found this several weeks ago. archive.commercialmotor.com/article/20th-september-1968/101/gt-leyland-for-1970
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Post by Deleted on Jun 22, 2015 14:16:54 GMT
They are like buses, you don't see one for ages then loads come along at once.
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Post by petervdvelde on Jun 22, 2015 19:04:20 GMT
Steve,
I did the test with an old mount. What i mean is that the total deflection before the bump stop is reached is 6-7mm and that the deflection due to the weight in static condition is already 3mm which leaves 3-4mm movement for the dynamic load due to uneven road. speed bumps or braking. So when the car is on its wheels (with the deflection being 3mm), the brake lines and steering housing should be fitted stress free and then when driving, the maximum dynamic deflection of the mounts is 3-4 mm before the bump stop is reached and this 3-4mm will be the maximum movement the steering housing and brake lines will make into that direction. In the opposite direction, the movement will nit be more than 3mm, except when the car is jacked up, using the jacking point.
Resurgam, The point i made was that even with old mount (which are not so badly rusted like Steve's), the movement isn't that much as the mounts very quickly get to the bump stop and therefore the movement is not that much. Newer mount could improve things as long as the deflection to the bump stop is identical.
Peter
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Post by Steve P5b on Jun 22, 2015 19:21:13 GMT
Thank you Peter , quite interesting but I can't quite follow the "bump stop" bit. Do you refer to the lower radius arm rubber bump stop?
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Post by petervdvelde on Jun 22, 2015 20:03:43 GMT
Steve,
I don't mean the bump stop on the radius arm but i mean that the deflection of the mounting doesn't get any further when more load is applied to the mounting.
Peter
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Post by johnwp5bcoupe on Jun 22, 2015 20:18:32 GMT
But if driven quietly and sedately it's not an issue for the traditionalist restorer who is content with the quality of the ride. I agree Vince
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Post by Steve P5b on Jun 22, 2015 20:28:36 GMT
Steve, I don't mean the bump stop on the radius arm but i mean that the deflection of the mounting doesn't get any further when more load is applied to the mounting. Peter OK, I understand now. However the mounting under test in my vice could be collapsed completely but the force I applied could be more than it suffers on the car but have no way of measuring the applied force on the car. I've been thinking of fitting a device to measure the maximum deflection on the car when its driven, like a "tell tale" however a camera looking at a mounting is going to resolve this issue I feel, so that's the next plan of action for me. Might take while to get organised though. But will give it a go.
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Post by petervdvelde on Jun 23, 2015 6:50:29 GMT
Steve,
You could use clay to check the deflection during driving. Just attach a bunch of clay between body and subframe and then go for a drive and see afterwards how much it is deflected. Toy shops sell a sort of clay which doesn't harden and this could be used. Not a high tech solution but could give the required info I used this clay when i had troubles with fitting door seals. It gave me info on high and low spots and estimate how thick the door seals should be in certain area's.
Peter
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Post by Steve P5b on Jun 23, 2015 7:15:15 GMT
Good idea. Playdoh would work, I can feel a visit to the grandchildren about to happen!
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Post by enigmas on Jun 23, 2015 9:14:04 GMT
I think 'plasticene' may be easier to use than playdough Steve as it will adhere to the subframe!
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Post by Steve P5b on Jun 23, 2015 17:10:06 GMT
I think 'plasticene' may be easier to use than playdough Steve as it will adhere to the subframe! Plasticene maybe too hard and offer too much resistance for my poor old mountings
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Post by Phil Nottingham on Jun 23, 2015 17:18:08 GMT
Seems more like a mod to me
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Post by johnwp5bcoupe on Jun 24, 2015 9:14:05 GMT
Seems more like a mod to me There seems to be an element of making/hijacking threads to justify the modification of the design of original parts "not because they are not available" but for the sole purpose of altering handling etc!! Phil and myself have "no problem" with this as long as it is in the correct section!!! IMHO it tends to confuse the members who just want to maintain the car if they can with standard parts.
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Post by JohnC on Oct 22, 2015 12:45:38 GMT
I love the Forum it's full of excellent information and alternative approaches to keeping our cars on the road. I took my 68 Coup P5b for it's MOT on Friday (Passed) with just an advisory. The body mounts were starting to deteriorate due to oil contamination. I went straight to my mannual to read up on these mountings. However as usual there was already a full debate on the forum. my only question, which may have been covered and mised by me is. Where can I get replacement mounts, are there different sizes for different models and out of ten how difficult are they to replace.
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Post by Roy of the Rovers on Oct 22, 2015 13:02:25 GMT
Wadhams does them and they are tricky and time consuming to replace, not impossible.
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Post by JohnC on Oct 22, 2015 14:06:43 GMT
Wadhams does them and they are tricky and time consuming to replace, not impossible. Thank, seems like a job for the winter with the garage door closed, so no one could hear any dad language and the heater on, so it does'nt hurt when the spanner slips and I hit my knuckles. Thanks once again.
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Post by Roy of the Rovers on Oct 22, 2015 14:45:00 GMT
Wadhams does them and they are tricky and time consuming to replace, not impossible. Thank, seems like a job for the winter with the garage door closed, so no one could hear any dad language and the heater on, so it does'nt hurt when the spanner slips and I hit my knuckles. Thanks once again. John if it doesn't make you bleed, you're not doing it properly! (Or is that just me?)
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