I always apply the handbrake firmly, probably too firmly, and leave the car in gear as well.
Quite a few years ago I took my Triumph to a small garage in West London to get the gearbox repaired.
When I returned to collect the car it was parked in the road, left in first gear and with the handbrake off! I guess there's some logic there somewhere.
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I have always left mine in gear, my Dad taught me it was the correct procedure when I was learning to drive. Now I have got to leave my current car in gear; its a Saab so cant get my keys out if I dont! I used to sometimes leave my girlfriends car in gear when I parked it, and get told off, because she never did and sometimes forgot to check it was in neutral before starting the engine...
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Always I have always believed it to be a good habit.
If the car is stopped when the handbrake is applied and the engine is off when the car is put in gear and the car is put into neutral before restarting how can it be harmful?
If it stops the car running away once in a thousand times that I park it that must be worthwhile. (thinking about it I guess I park the car at least 1000 times a year.
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Always in gear. Was one of the first things Dad taught me (BSM taught me to pass the test- Dad taught me to drive). As a result have never started a car without clutch down.
Really infuriates me as my wife refuses to leave the car in gear when parked. She doesnt put the clutch down so says I have to leave her car like that or risk damage to the garage. Have tried to get her to change this habit- but she's far too stubborn.
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I never used to leave my car in gear - just trusted the handbrake.
However, (probably due to something I read in the Backroom) I now tend to leave the car in gear if it is parked on a slope.
My question is whether (or in what circumstances) I should leave the handbrake off when I leave it in gear.
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My question is whether (or in what circumstances) I should leave the handbrake off when I leave it in gear.
The one situation I do this is when I am leaving a car parked up when I know it will be for a few weeks or more. Handbrakes can stick, especially in older vehicles, cars don't stick in gear
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Always leave my own cars in gear. Always have to remember to leave the site cars we have here OUT of gear, as many folk don't check for neutral or depress clutch before starting....
Particularly important on Xantias, that have a habit of running away....!
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RichardW
Is it illogical? It must be Citroen....
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Always in gear and if on a slope I leave the wheel pointing slightly in to the curb.
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I very rarely leave it in gear, unless parking on a steep hill. Call me old fashioned but I thought brakes were for stopping the car and gearbox was for helping the car go?
Having driven for close to 20 years, parking with just my handbrake, I have never come back to my car to find it has rolled away.
Incidentally, what damage (if any) would get done to the gearbox if your car either gets a gentle or more serious bump whilst left parked in gear?
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And should add of course, that if I had to start parking in gear now, there is not a hope in hell of being able to "train" SWMBO to do the same !
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With my car (automatic) I leave it in Park with the handbrake on. It's a bit like having two handbrakes lol. With manual cars I only leave it in gear only on hills. I also turn the wheels into the kerb.
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Always use park in the autobox, even with the old one that doesn't need to be in park to get the key out, and use the technique mentioned above to take the strain off the transmission. I was always told to leave a manual in gear too.
IIRC Mk II Jaguars 40-odd years ago often used to take off on their own as the back discs cooled down, unless left in gear as well.
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In gear. Handbrake on. Starting as Oz.
Many years ago came out of shop to find car 30 yards further on down a slightly sloping road resting up against the back of another car. No damage. Very embarrassed. Used gears ever since.
Daughter does same and was OK until a dustcart pushed her car up onto the pavement. Said box was never the same afterwards. The gearing is not good for that.
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>>Incidentally, what damage (if any) would get done to the gearbox if your car either gets a gentle or more serious bump whilst left parked in gear?
On a manual, virtually none, because the gearbox is only loaded by the friction and residual cylinder pressures in the engine. Or put another way, the load required to turn the engine over is negligible in comparison to the loads the gearbox normally handles.
Number_Cruncher
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On a manual, virtually none, because the gearbox is only loaded by the friction and residual cylinder pressures in the engine. Or put another way, the load required to turn the engine over is negligible in comparison to the loads the gearbox normally handles.
BUT this theory totally goes out the window when its hit by a car at 15mph or more. The engine CANT (as in not possible) accelerate from 0-15mph in milliseconds. It might as well be locked solid. That leaves all the week spots in that chain, most of which will be in the transmition If your are lucky the drive wheels will be locked and skid along the road.
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TourVanMan TM < Ex RF >
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Yes, you're right, I was thinking of the more frequent and gentle parking type knocks.
In a faster impact, you will get a torque spike that is proportional to the velocity of impact, and also to the square root of the effective engine inertia multiplied by the effective transmission stiffness - so, possibly a short lived, high torque, which at some level of impact speed will begin to do damage if some other part doesn't slip first.
Number_Cruncher
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Hmm I wonder at what level we are looking at? my 15mph was hypothetical. (ie finger in the air stuff)
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TourVanMan TM < Ex RF >
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As is my wont, (and it's Friday afternoon, and I needed some fun!) I've thrown numbers at the question.... lots of them!
Until I included a check in my calculation for the wheels skidding, it was looking horrible, with a large potentially damaging torque spike even under 5 mph impacts.
Once the wheels can skid, even with high values of mu, the torque becomes acceptable again - this makes some sort of sense as the wheel skidding condition may be used in the sizing of transmission parts.
Number_Cruncher
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So with the wheel skidding factored in,
Is it safe?
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TourVanMan TM < Ex RF >
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Yes, I'm fairly sure it's OK
I've just thought of something I've left out of my sums - which actually makes it even safer - which is that the engine and transmission will rotate as a unit on the mountings, so this will act as another compliance to include in the stiffness calculation.
Number_Cruncher
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>> Until I included a check in my calculation for the wheels skidding, it was looking horrible, with a large potentially damaging torque spike even under 5 mph impacts. Once the wheels can skid, even with high values of mu, the torque becomes acceptable again - this makes some sort of sense as the wheel skidding condition may be used in the sizing of transmission parts.
Too many variables surely, the deformation charateristics of both vehicles, the flex and damping characteristics of the engine/transmission mountings etc. I would hazard a guess that the torque spike would be disapated by the progressive deformation of one or both vehicle to the extent that it would take a collision of rather greater than 15mph for the acceleration of the drive train to cause any mechanical damage. At which point the structural damage would make any such mechanical damage seem insignificant anyway.
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>>Too many variables surely...
Yes, you can say that about virtually anything, but all I'm up to is using a simple model to get a rough order of magnitude idea of what is going on. My model is so simple, it isn't even based on any particular car.
Even though the model is simple, its output has surprised me, and it has caused me to reappraise my earlier answer. This, for me, is the main puropse of numerical modelling; I don't usually spend much time producing a complex model including every last detail, that's much too academic, and isn't often a valuable investment of time.
>>I would hazard a guess...
I don't know how you make your living Cheddar, but one thing I have learnt in engineering is that guesses and hunches which at first seem obvious can turn out to be hugely wrong when the part is on the test rig!
Number_Cruncher
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>>I would hazard a guess... I don't know how you make your living Cheddar, but one thing I have learnt in engineering is that guesses and hunches which at first seem obvious can turn out to be hugely wrong when the part is on the test rig! Number_Cruncher
I agree NC hence the need for a test rig, within a forum such as this hazzarding a guess does no harm however the same cannot be said of a test lab or design office.
Nevertheless I would be interested in the definative answer, two typical vehicles, one parked in gear, the other hitting it at 15mph, if the stationary vehicle was hit from the rear and the handbrake was on then that would reduce the load imposed on the transmission if the car was also in gear, additionally the deformation of both vehicles impact areas would also absorb a lot of the energy as would the flexible mounting of just about every component through to the engine itself. Then it comes down what gear the vehicle was left in and the applicable gear ratio, after all if the car was in a higher gear then the wheels could move more for only a small movement at the engine, then there is the compression ratio of the engine, how much energy it requires to turn the engine over etc etc.
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Which would cost the most? A recon gearbox fitted or someones funeral?
Handbrake on, in gear always
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2 Dirty VW diesels and a Honda with an 18 inch blade
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One way to approach this kind of problem is to carry out what may be described euphemistically as a "conservative" calculation. The idea is, you make a series of "safe" assumptions which simplify the model. Then, from the model, you get one of three possible outcomes;
1) Even with all the safe assumptions and a simple model, you find there is no real problem - no further action required, the first pass assessment is enought
2) The model shows some borderline problem - probably by removing some of the conservative assumptions and making a more complex model, you might be able to analyze your way out of trouble.
3) The conservative model shows that the part you are considering will be doomed as soon as the event you are considering happens - in this instance, you probably need to beef the part up - in order to determine by how muvh, you probably need to remove some conservative assumptions from your model, or else you will end up with something Victorian in its proportions!
So, my extremely simple analysis used the following conservative assumptions;
The vehicle concerned goes from zero to whatever speed instantaneously at time t=0
The gearbox stiffness is infinite
The gear ratio between driveshaft and engine is 12
The engine inertia (which itself is a conservative estimate) is referred to the driveshaft
The tyre longitudinal stiffness is 7e5 N/m
The suspension longitudinal stiffness is 5e5 N/m
The driveshaft stiffness is calculated on the basis of being a 80cm long 40mm dia solid steel shaft
The vehicle mass is 1500 kg
The model then estimates the torque in the driveshaft, using the formua I hinted at higher up in this thread. Where I overestimate a stiffness (or even ignore one), this increases the torque value the model predicts.
To determine if there was a problem, I then compared the predicted driveshaft torque with a level which might be expected from the engine. I found that even at low speeds, the torque in the driveshaft became (very) large when compared with reasonable numbers.
So, this is when I included the idea of the wheels skidding.
The transmission is sized for static strength on the basis of the maximum torque which might be expected to occur in the driveshafts. For many FWD cars, this is limited by wheelspin, and the sizing criterion will be the skidding torque multiplied by a safety factor. Of course, the transmission parts are also sized on the grounds of fatigue performance, but, as this is a one off event, that isn't an issue here.
This means that the driveshaft will withstand slipping torque whether caused by the engine or by an impact - increasing the complexity of the model will not affect his conclusion.
Or, said another way, my model is, in the real world, utterly worthless, and I should have thought more about how these parts are sized during the design process.
Number_Cruncher
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Or, said another way, my model is, in the real world, utterly worthless, and I should have thought more about how these parts are sized during the design process
Ok now lets look at it another way. Assume that your average car does 30 mph / 6k revs in first.
Now how many times will a transmision survive a sudden clutch dump (as in side step your foot off the clutch) at 6k revs? Many a car has been instantly broken by car journos doing 0-60mph times this very way. (in this case all we are doing is putting in the torque spike from the other end of the drive chain)
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TourVanMan TM < Ex RF >
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Yes, I think you're right - dumping the kinetic energy of the rapidly spinning engine into the transmission as well as the max torque condition is an extra load that for most users of motor cars is irrelevant. Cars designed for this condition would have bulkier transmissions. In many cases, the safety factor covers this type of one off behaviour, but not always.
If this is a design case, I would be surprised if the number of applications of this brutality is more than 10.
My reason for saying this is based on a completey different extreme design case. The suspension of the Ford Transcontinental was based on riding up a standard kerb fully laden at 30 mph - the design case was that the truck should withstand this abusive behaviour 6 times.
Number_Cruncher
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Incidentally, what damage (if any) would get done to the gearbox if your car either gets a gentle or more serious bump whilst left parked in gear?
But if your car gets a "more serious bump", the front or rear could be stoved in and require an insurance claim. So if gearbox damage was to occur, this could be dealt with by the claim.
:o)
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Indeed but would you know at the time! the damge could be hidden
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TourVanMan TM < Ex RF >
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