l0rd
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| posted on 28/9/08 at 06:46 PM |
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Rubber Engine mounts
Been thinking about it for a while.
99.9% of cars have rubber engine mounts in order to minimize vibrations.
I remember a Corvette that was directly bolted on to the chassis.
Has anyone tried to fit the engine without these?
Am i thick for concidering?
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Thinking about it
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| posted on 28/9/08 at 06:55 PM |
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What engine?
Why do you not want to use rubber mounts?
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ReMan
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| posted on 28/9/08 at 07:11 PM |
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"Am i thick for concidering?"
No but you may be slightly spellingly challenged for considering?
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loggyboy
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| posted on 28/9/08 at 07:53 PM |
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Its common to get tougher ones for competition cars, and cars like BTTC etc have them bolted directly to the chassis, but the car needs to be
incredibly strong, as most cars would be shaken to peices by the vibrations, not even to think of what it would do to the occupants!
I reinfored my rubber engine mounts by filling the gaps with polyurthane marine sealant. It was a happy medium between to harsh (and expensive) comp
mounts and the original originals.
Mistral Motorsport
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mark chandler
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| posted on 28/9/08 at 08:41 PM |
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If you bolt directly the engine becomes a stressed member and improves ridgity in the car which is a good thing, but can cause stress cracks,
vibration etc.
I made up brackets using suspension bushes, although with modern bike engines you can generally bolt in directly with no ill effects as that what
happens on some bikes.
Car engines are really just not smooth enough although it can be done.
I knew a chap that raced a landrover with a tweeked 200tdi engine that was bolted in solidly, he had so much meat pulled of the flywheel it was the
only way to stop the thing jumping about, car rattled and shaked.
Regards Mark
[Edited on 28/9/08 by mark chandler]
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ReMan
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| posted on 28/9/08 at 08:47 PM |
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Even bike engines, particularly bigger ones, which are much smoother, tend to be rubber mounted these days.
I would look at rubber mounting my next BEC, , BUT, you have to be careful as some are designed to be solid mounted and may not have the strength in
the mountings to cope with a twisting motion diffent to the original design
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l0rd
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| posted on 28/9/08 at 09:02 PM |
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Oupsss. I feel embarrassed for making a spelling mistake 
I will be using an MX5 1.8l engine for my car when i finally start.
I was just wondering if anyone else tried it, advantages and disadvantages of it.
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clairetoo
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| posted on 28/9/08 at 09:44 PM |
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Advantage's - the engine could be used as a `stressed member` , helping to stiffen the front of the chassis .
Things could be run a little closer - no engine movement could mean room for a bigger engine
May be a little lighter ?
Disadvantage's - all the harshness and vibration will go direct into the chassis , so it could be very unpleasant to drive , as well as leaving
a trail of detached part's in it's wake....
Its cuz I is blond , innit
Claire xx
Will weld for food......
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ReMan
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| posted on 28/9/08 at 09:57 PM |
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quote:
Originally posted by l0rd
Oupsss. I feel embarrassed for making a spelling mistake
Please don't, it was only a joke, hence the smileys. But I think you know that.  
What is it that is driving your desire to solid mount a car engine then? Are you considering some advantage fom it in your project?
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MkIndy7
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| posted on 28/9/08 at 10:29 PM |
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Phew i've found my post from ages ago to save typing it all out agian:
I'd be careful with the Grade of Nylon/polyurathane that you get.
The engine mounts for my Tin-top were specialist ones and they would only sell you the full kit (when only 1 was split!, the same conversion mounts
"loggyboy" was talking about).
We went to a local Plastic suppliers and they said "yes we've got just the stuff they use this on the Focus WRC car" and my GOD
could I believe it.. the engine might as well have been bolted to the chassis it shook everything!
Whatever the hardness its measured in I think that was 90 and what i've got now is about 40-50 and its still far too hard really the engine
still doesn't really move when rev'd or when load is put on it.
I'd try and stick to something commercially available as Engine mounts.
Since this even that 40-50 Grade was a bit too harsh so they've had circular holes punched through them between the crush tubes and the outer to
try and make them even more compliant.
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l0rd
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| posted on 29/9/08 at 07:31 PM |
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The only advantage i can think of is the massage from the engine to my back 
I am just curious if i should consider this or not.
Plus, somewhere on the back of my mind i have the accident of the guy with the Westfield a couple of weeks ago that was saying that the engine was
detached from the car and ended down the road.
My with my small brain, the only part that would fail for something like this to happen would be the engine mounts - rubber mounts?
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David Jenkins
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| posted on 29/9/08 at 09:06 PM |
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Sometimes the original rubbers were too soft for a kit car, and people (like myself) found stiffer alternatives. Engine vibration is noticeable - not
excessive, but I wouldn't want it to get more intense. I definitely wouldn't want rigid mounts!
My engine mounting rubbers came from a Land Rover, I think...
[Edited on 29/9/08 by David Jenkins]
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MkIndy7
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| posted on 29/9/08 at 11:09 PM |
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I think bothering weather the engine is still attatched after a crash of that magnitude is the least of your worries! 
Would it not be of benefit in disipating energy and the car weighing less after its flown off be a bonus if anything?
You could always try and teather the engine across the bushes if it bothers you that much, but i'd really want some flex in there somewhere.
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Syd Bridge
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| posted on 30/9/08 at 10:02 AM |
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I'd rubber/polyurethane mount a road engine, without question.
A couple of words of caution about hard mounting...
The competition engines you see hard mounted will have been professionally balanced, to eradicate any internal balance problems which cause vibration.
Any harshnesses transmitted to the chassis are then only due to torsional cycles.
Be careful how you mount a hard mounted engine. The normal cast in engine mounts on a block may well not be up to the job, and the block will crack
eventually. This is why you see rigid mounts as big plates across the front and back of the block.
Most car engines are not intended to be used as stressed members, and hard mounting can cause stresses which can upset anything from crank alignment
and bearing failure, to constant head gasket failures. (Ask me how I know this one!!)
The factory rally cars and other competition cars using road engines as stressed members, usually use specially cast blocks, which may look like any
other externally, but are cast with a lot more metal in the relevant places.
Best to use a good quality aftermarket competition polyurethane mount, and know that your engine will stay in one piece, and your car, and most of all
your spine.
Cheers,
Syd.
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