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# metal thickness

### Tech Articles

Discussion and questions related to the course Motorsport Fabrication Fundamentals

how would you go about the maths involved for metal thickness when creating an engine mount or trans mount? is there a specific formula to figure out thickness based on weight/load on the mount.

Sure there is. You can search for beam/bending calculators. Try looking for "steel sheet stiffness calculator", and look at a few of the top google results.

But often it's easier to just look at what's been done, and copy that. 8-10mm plate steel would be used for a typical motor mount. Looking at what oem cars use as a guide.

The calculation you're looking for will depend on the geometry of the mount and where the loads will be placed on it. Do you know the geometry of the mount that you're hoping to make?

There is quite a bit of work involved in these calculations so depending on your situation it may be a better use of time to buy an existing mount and modify it to suit your application.

A few points that may need to be considered -

Don't use the engine torque for calculating the forces on the mounts*, use the engine peak torque, multiplied by the first gear ratio and if an automatic is used multiply that by another 2.5 for the torque converter multiplication/ clutch drops.

Then multiply by the safety factor you're happy with.

On that, if using some form of insulator/isolator in the mounts, make SURE they're of a captive design that will physically restrain the engine's movement in case of failure - also adds safety as the engine is less likely to break loose in an impact.

Regarding impacts, don't forget to make allowance for the longitudinal braking, acc'n, and potential crash loads - some may prefer to make the mounts very stiff so the engine assembly doesn't move, others may prefer to have some movement to absorb some impact energy.

The gearbox/tailshaft housing mount 'should' be relatively lightly loaded, as it's basically just supporting the weight, but impact loads can be significant in a crash, or a hard 'bottoming out' over bumps and yumps.

I'd also suggest giving some serious thought to the way the engine/gearbox assembly is fitted and secured - if it's easy-ish to fit the assembly into the car/chassis, and access the fasteners, it can make a big difference in working on the vehicle if either/both need to be pulled - ESPECIALLY on a hot engine! Things to be aware of are the exhaust routing, clutch and/or gear sector access, cooler lines, etc.

On a related topic, potentially modifying the bellhousing/transmission floor, if required, for easy access to the fastenings can save time and knuckles, and if it splits between the gearbox and bellhousing, modifying for a quick rlase may be worth it, if they normally bolt together from inside the bellhousing.

*The engine mounts have to resist the driveshaft torque, remember.

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