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Engine Mounting (With Vibration Reduction)

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Syndrome View Drop Down
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    Posted: Sep/01/2018 at 5:26am
Hello everyone,

I am new to the forums and Baja so pardon for any silly mistake/question :P

I am trying to design an engine mounting for our vehicle which could reduce vibrations transmitted to the roll cage from engine (although damping isn't really required, vibrations were really annoying in our previous vehicle)

Initially I considered using rubber for reducing vibrations, but then I read on forums that the teams that actually implemented this faced a play in C2C distance of CVT due to rubber. Hence they designed a flexible mounting (c2c adjustable) mounting.
 
Now I am having way too many ideas without much methods to validate them except ANSYS.
The first mounting I designed was a sandwich comprising of 2 steel plates, between them was a rubber block (equal dimensions), which was mounted on the roll cage, and upon which the engine was mounted. 

https://i.imgur.com/7dlKXGt.jpg

However machining this would be difficult hence I came up with another idea : isolation using mounting the engine on a steel plate, and then mounting that plate on square steel rods (which would then be welded to the frame) using bolts seated on rubber. ANSYS does show promising results (as in static structural; only 0.02 mm deformation in xdirection which I don't really think would mess up my C2C), but I'm still not sure whether it'd be a wise decision to implement it or not. 
Moreover modal analysis of this design gave the first mode of vibration at 316 Hz, and without rubber the same design gave the first mode of frequency at 313 Hz, so I'm not so sure whether using rubber is even worth it or not.

https://i.imgur.com/WvfEQXd.jpg

And as far as C2C flexible mounting is concerned I've been thinking of cutting slots in a steel plate and mounting the engine on those slots using bolts (so I could adjust C2C), and then mounting that steel plate on steel members with some kind of rubber. I could also use a leadscrew for C2C adjustment (which I read about on the forum but couldn't find any image showing so).

What type of mounting do you use ? Please show with pictures. Also any advice/suggestions would be appreciated.
Thank you.


Edited by Syndrome - Sep/01/2018 at 5:29am
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RLM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Sep/04/2018 at 8:09am
if your concerned about your C-C distance, why not just isolate the entire driveline from the chassis? that way the gearbox and engine can be mounted rigidly relative to eachother, but the whole system is dampened between it and the chassis.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Syndrome Quote  Post ReplyReply Direct Link To This Post Posted: Sep/04/2018 at 2:42pm
Originally posted by RLM RLM wrote:

if your concerned about your C-C distance, why not just isolate the entire driveline from the chassis? that way the gearbox and engine can be mounted rigidly relative to eachother, but the whole system is dampened between it and the chassis.

Thanks, I've been thinking of a sub-frame design too recently.

How would I dampen the vibrations though? Do I need to mount the entire sub-frame on rubber pads/blocks throughout the entire sub-frame base, or bolting points or something else?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Sep/05/2018 at 8:07am
That is for you as an engineer to figure out. As per the rules, I as a subcontractor cannot design your vehicle.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sujandinesh Quote  Post ReplyReply Direct Link To This Post Posted: Sep/05/2018 at 11:47am
Rightly said. 

In addition to removing the vibrations at the source (engine), you can also think of ways to reduce the vibrations where your driver is experiencing them the most. 
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