# Gyroscopic effect in a horizontal axis IC engine

1. Oct 18, 2013

### marellasunny

My tutor says Henry Ford opted for a horizontal-bed IC engine for the Model-T as this would avoid having any gyroscopic effects(normally associated with a vertical oriented engine).

My question is,how does it matter if the engine cylinders are oriented horizontally or vertically?since the crankshaft is rotating anyway and would produce a gyroscopic effect nevertheless,right?

As a extreme example of my understanding of engine gyroscopic effect,I would like to cite the rotary engine of the plane 'Sopwith Camel', which produced so much gyroscopic effect that the plane went 'up' on left turns and 'down' on right turns.But,this was because there were 8 cylinders revolving around a stationary crankshaft.

In case of the Model-T,the cylinders were stationary,so how would these produce a gyroscopic effect?

2. Oct 18, 2013

### etudiant

Interesting question.
As the crankshaft and flywheel are the only significant rotating elements that I can think of, maybe your tutor is mistaken.
Have you asked why s/he believes this? Maybe s/he was told this long ago and has never really thought about it.

3. Oct 18, 2013

### SteamKing

Staff Emeritus
The rotary aircraft engines used in WWI had 9 cylinders.

The horizontal placement of the engine in automobiles simplifies laying out the drivetrain. I don't think Ford was the first to use this layout. I think Panhard in France was the first to use the front engine - rear drive layout in about 1895.

http://en.wikipedia.org/wiki/Système_Panhard

Standing the engine on end has no benefit of which I am aware and quite a few disadvantages:
1. It obstructs forward visibility.
2. Adds another right-angle gear to the driveline
3. Complicates lubrication of the internal engine parts
4. In pre-electric starter days, makes it damned difficult to use a crank to start the engine
5. Upper cylinders would be difficult to lubricate
6. Hard to provide fuel using the simple carbs and gravity feed systems from the fuel tank.
7. Hard to cool with a conventional radiator

4. Oct 18, 2013

### Baluncore

I think this situation is one of angular momentum, not of gyroscopic effects.
A vertical axis engine would tend to cause significant directional changes to the vehicle when changing RPM or gear ratio.

5. Oct 19, 2013

### marellasunny

Why?
More specifically,does a larger gear ratio mean a greater/smaller rotational moment of inertia for the whole system? From my calculations,larger the gear ratio,smaller the overall rotational moment of inertia.
$$Gear. ratio=\frac{\omega _1}{\omega _2}$$,say 1 is the input shaft.

We know that,
$$\frac{\omega _1}{\omega _2}=\frac{n_2}{n_1}$$
where n-number of teeth on each gear [n1-number of teeth on input gear,n2-number of teeth on output gear]
omega-rpm of the gears
$$K.E_{system}=KE_1+KE_2=0.5J_1 \omega_1^2+0.5J_2(\frac{n_1}{n_2} \omega_1)^2$$

$$J_{system}=J_1+J_2$$

Therefore,greater the gear ratio,smaller the rotational moment of inertia of the whole system,right?

Q.Wouldn't a gearbox in a horizontal axis engine also have different moment of inertias at different rpms?

6. Oct 19, 2013

### marellasunny

Why?
More specifically,does a larger gear ratio mean a greater/smaller rotational moment of inertia for the whole system? From my calculations,larger the gear ratio,smaller the overall rotational moment of inertia.
$$Gear. ratio=\frac{\omega _1}{\omega _2}$$,say 1 is the input shaft.

We know that,
$$\frac{\omega _1}{\omega _2}=\frac{n_2}{n_1}$$
where [n1-number of teeth on input gear,n2-number of teeth on output gear]
omega-rpm of the gears
$$K.E_{system}=KE_1+KE_2=0.5J_1 \omega_1^2+0.5J_2(\frac{n_1}{n_2} \omega_1)^2$$

$$J_{system}=J_1+J_2$$

Therefore,greater the gear ratio,smaller the rotational moment of inertia of the whole system,right?

This now brings me to the question:
Q.How does it matter in relation to the angular momentum if the engine cylinder axis is horizontal(like a boxer engine) or vertical(like a inline 4)?

Q.How does it matter in relation to the gyroscopic effect if the engine cylinder axis is horizontal(like a boxer engine) or vertical(like a inline 4)?

7. Oct 19, 2013

### Baluncore

I think the OP has some confusion about referencing cylinder axis or crankshaft axis. It is the crankshaft that rotates and so it is the crankshaft axis that is the gyroscopic axis.

It makes no difference which way the cylinders are orientated since they reciprocate in a balanced way.

There are three simple crankshaft rotation axis orientations.
1. Traditional. In the line of the tail-shaft. When you rev the engine the car rocks sideways.
2. Transverse. When you rev the engine the car rocks less but in a front – rear way.
3. Vertical. When you rev the engine the car changes direction. Not an ideal situation. Changing gear changes RPM, therefore it changes rotational momentum and causes the vehicle to tend to change direction when changing gear.

8. Oct 19, 2013

### Baluncore

Correct. Rotary engines had an odd number of cylinders on a single fixed eccentric crank. The reason for an odd number of cylinders is that, being four stroke, the firing order could be regular. That is not possible with an even number of cylinders except with two stroke engines.

9. Oct 21, 2013

### marellasunny

Upon further clarification with the lecturer,he meant the gyroscopic effect was produced due to the flywheel.So,yes Baluncore,you were correct in saying that the crankshaft axis is the 'gyroscopic axis'.

**"Vertical crankshaft orientation axis"-is this even possible?Examples please.

10. Oct 21, 2013

### Baluncore

A great many lawn mowers are now built with a vertical crankshaft axis, examples are Victa, Flymo.

The oil seal at the bottom of the shaft is not such a problem with two stroke motor lubrication since an oil sump is not required.

There is an advantage with a gas turbine being mounted with a vertical shaft in a light motor vehicle as it would prevent wheels lifting off the ground when going around tight corners.

Last edited: Oct 21, 2013
11. Oct 22, 2013

### marellasunny

Twist to the tale,tutor says gyroscopic effects very negligible in today's drive-train format i.e with the flywheel occurring immediately after the engine.Reason given:there is no 'lever'/distance for the flywheel moment to act on and hence no gyroscopic effect.Says the only possibility is if the bearings are loose and the flywheel can move left/right.

This was contrary to my understanding that in order for the occurrence of gyroscopic moment,one needs :a.Yaw moment b.Rotating flywheel mass.

Is he right?

12. Oct 23, 2013

### AlephZero

I'm slowly coming to the conclusion that either your tutor doesn't know what he/she is talking about, or somebody's first language is not English and some terms have been translated wrongly.

13. Oct 24, 2013

### Baluncore

Your representation of your tutors opinion is hearsay. Your lack of vocabulary skills may have resulted in your tutor misunderstanding your question or in you misunderstanding their reply.

It would be more mature to approach the apparent inconsistency by asking where the misunderstandings are, rather than to make it personal by insisting the tutor is wrong. It is wise never to corner a rat. Your hostility and personal attack on a superior will alienate you from others. That would appear to be self destructive and counter to your best long term interests. To progress you need helpful allies, not enemies.

Professional etiquette requires that you respect professionals in your field. No professional is going to gang up with you against your tutor to prove your tutor wrong. If you do not respect others then you cannot expect to be invited to join that profession.

14. Oct 26, 2013

### marellasunny

Yes,thank you.I needed to be reminded of that.Conscience didn't feel right when I left the room with doubts still lingering,should have gone back and cleared them out.Hope the administrator comes-up with a category called 'ethics in academia'.

F.Y.I:I am not being sarcastic.