Engine torque reaction logic

[cardiffrob]

Hellooooo.

I've managed to tear a new rubber engine mount (on a Morris Minor!!!!!) and have knocked up a rod to tie the top of the engine through a rubber bush to limit movement, rather like the one used on Morris 1000s. Now, if I stand at the front of the car the engine rotates the crank clockwise. The tie rod on the Morris 1000 goes from the top of the engine to above the (UK) drivers' feet. Am I correct in thinking that this tie rod is going to go under compression? I've been forced to put my own one to the other side of the engine bay. Carb is off at the mo so I can't see what it does.

The reason for my concern is that me new engine has only one stud available to mount the tie onto and that if the rod was under compression it might kink the tie rod around the rubber bush. I can't for the life of me see why the factory used the same tie rod under compression, unless I'm turning thick and have got it all wrong.

This is the factory design. Is it being pushed or pulled???

Mine is more like this...

 

[Lufbramatt]

What way does the prop shaft turn?

 

[roofman]

Logicly thinking the motor should want to pull away from rotation direction..so motor rotation clockwise... motor pulls or leans anti-clockwise

 

[cardiffrob]

So, the engine in the first pic would be compressing the tie rod if the crank went clockwise if viewed from the front. Seems a little crazy to have it in compression rather than tension. Surely it would require more 'meat' on it under compression to allow for the possibility of it bending?

 

[gordon stephenson]

Looks to me like that angle bracket won't last too long, probably fatigue at the point of the two studs attaching it to the head, Better if you design the bracket so that the tie rod pulls/pushes directly in line with the flat on the head where the two studs are,

 

[waddycall]

Isn't it always going to work both ways? Under power and on the overrun, gear shifts etc.

 

[roofman]

Isn't it always going to work both ways? Under power and on the overrun, gear shifts etc.

yep plus in reverse

 

[cardiffrob]

The top picture, Gordon? That's the factory design, although the engine bracket in that pic is not the original one but very similar. Only one fixing at the head end.

 

[piman]

Hello Rob,

it will be under compression, which is not a bad thing. Your picture is showing the link incorrectly fitted, the engine bracket is upside down. You can see the bulkhead mount is misaligned.
Bear in mind there is not a lot of torque on a Morris Minor engine even in 1098 form.

Alec

 

[roofman]

lets not forget here we are talking about a 3 HP morris motor not a 300HP scooby motor...99% of engines from the same era made do with 2 lower engine mounts and 1 gearbox mount

 

[cardiffrob]

Good point about reverse. So it is all about the direction of rotation of the propshaft, not the crank. Got it!

So, which scenario creates the greatest tearing force? 1st/reverse at full chat or top gear at full chat? I presume the former. I'm still trying to get my head around something that you'all probably think is easy. I'm having a 'stupid' day.

Thanks for being patient!

 

[roofman]

Good point about reverse. So it is all about the direction of rotation of the propshaft, not the crank. Got it!

So, which scenario creates the greatest tearing force? 1st/reverse at full chat or top gear at full chat? I presume the former. I'm still trying to get my head around something that you'all probably think is easy. I'm having a 'stupid' day.

Thanks for being patient!

Once on the move there should be almost zero torsional movement and dont forget the classic "to every force there is an equal and opposite reaction"

 

[BrokenBiker]

Good point about reverse. So it is all about the direction of rotation of the propshaft, not the crank. Got it!

So, which scenario creates the greatest tearing force? 1st/reverse at full chat or top gear at full chat? I presume the former. I'm still trying to get my head around something that you'all probably think is easy. I'm having a 'stupid' day.

Thanks for being patient!

if you are likely to be using every gear at full chat quite often then i would consider a slightly different form of engine mounting/torque control

 

[cardiffrob]

The new rubber pulled apart during a gentle reverse out of the driveway, under tension. Looks like I've got the rod the right way round on my one. Phew!

if you are likely to be using every gear at full chat quite often then i would consider a slightly different form of engine mounting/torque control

Full chat still isn't much. Maybe 40 bhp maximum from my engine. Full chat with this is like idle from a modern car. 0-50 is said to be 50+ seconds and 60 is not possible without modification (which mine has) so the engine mounts aren't a very sturdy design

 

[BrokenBiker]

The new rubber pulled apart during a gentle reverse out of the driveway, under tension. Looks like I've got the rod the right way round on my one. Phew!


Full chat still isn't much. Maybe 40 bhp maximum from my engine.

ah fair enough...for a moment i thought you may have dropped something a bit more meaty in there causing the issues...can you not re-make the mounts to be stronger/firmer?

 

[cardiffrob]

Time/cost etc. it would be nice to get some done but if my 'bandaid' tie rod works I'll be happy. I looked up the part number for the engine mounts and the same items were later used as gearbox mounts on the later Minor so there might even be some Poly ones available somewhere. More Googling tomorrow, methinks.

 

[BrokenBiker]

Time/cost etc. it would be nice to get some done but if my 'bandaid' tie rod works I'll be happy. I looked up the part number for the engine mounts and the same items were later used as gearbox mounts on the later Minor so there might even be some Poly ones available somewhere. More Googling tomorrow, methinks.

upgrades would be easier, but making them wouldnt take that long really...especially if you just did a bit a day...i am always surprised at how quickly some things come together when ive been putting them off for ages because they seem like a lengthy job

 

[gordon stephenson]

On closer inspection I can see it is only mounted on one stud. the bracket in post 8 looks as if it will operate on a better plane.

 

[cardiffrob]

I agree, Gordon. That's the engine-end bracket shape I'm using for mine.

BB. I know what you mean. I'd been putting off making the frames for the sidescreens for ages. Rydal bar (I had to Google it, too) bent into shape. Took less than 40 minutes to make each one. Amazing how easy it was to form with just a bench vice and a BFH. I don't think the old ones would have survived much longer! The rusty one was in the canvas sidescreen in the second shot. I used it as a template to make a new one for someone else and have BHH'd an old 4-door rear stainless window frame to make a stainless sidescreen for my own car. They want nearly £250 each to 'canvas-up' an original sidescreen. Eeeek!