bassboy

hi peeps, have got my Automotive Eng exam on wed and going through the past exam questions...looking through my notes there is nothing about gearboxes so was just wondering if you could give any help with the following questions:



with question b, is it refering to gear types like helical, semi helical etc, or is it referring to the box type?

and im clueless about how to go about C D and E

can anybody help?

bassboy

neone?

bassboy

markk

iTrader: (2)

wheres your pic of the box ? thats just the diff , if the 4th gear is 1:1 the drive is straight through the box

b, helical, semi helical, straight cut ? is that what they want ?

c 130/0.4*105=220nm ?? would be a guess tbh without lookint through my old data

d 1- pinion
2- planet gear
3 - cross pin
4 - sun gear
5 - speedo drive gear
6 - speedo drive pinion
7 - crownwheel


i'll do the last one in a bit !

M Brian

eek

its only been a year and im so out of it...

yeah youre right with b)

i'd go straight - no side loads, noisy, high wear (I think)
semi helical - thrust loads,
double helical - quieter, expensive to produce, even wear

you need some gear ratios to work out E I think but you would do it using the outside wheel as the inside will be spinning slower?

bassboy

cheers for the replies...looking through the paper thats all the info they have provided us with...nothing more

are the above answers def correct?

bassboy

markk

iTrader: (2)

the answer to E - 391
406/376 = 30 /2 ( each sun gear ) = 15 + the slower running wheel (376) = 391, 406 - 15 = 391 crownwheel speed is 391rpm


helical gears have a greater sruface area than straight cut, semi helical have a reduced side loading but are noisier, straight cut have no forces outward just against the teeth but are very noisy in operation

as for the three shaft diagram dont know if i can draw it on here





server keeps removing my spaces and compacting things - see if writing space help !

ok version 2 !!

Sean_RS

lol can i post up one of my marketing or strategic planning questions....

M Brian

it says continued though? so does that mean the paper or just the question?

what level is this mate? ONC HNC or something?

as part C seems a bit odd as there is no reference to the actual size of te friction plate? just the mean? i.e. point its acting on and its only worth 2 marks so must be a simple calc.

i.e. T = Pressure x friction x radius of gyration x number surfaces

so id make it = 130000n/m^2 * 0.4 * 0.105m x 2 (two surfaces on single plate)

and end up with 10.92 KN??

sorry but memory really not good! lol - what notes have you got?

im still not sure on E either lol

M Brian

mark....

can you explain for me what youve done in E?

GARETH T

wouldnt e be the average of the two? (add them up and devide by 2)

markk

iTrader: (2)

i thought i had

if the inner wheel rotates faster than the outer on the turn - ok

the sun gears/planet gears must be equal or the diff would explode let alone not mesh so the calculation must equal both wheels speeds together , just because the car is cornering the crownwheel doesnt speed up - it cant - its meshed with the pinion which in turn is meshed with the selected gear - so imagine the car is in a straight line , divide the highest from the lowest then divide that by two, then equalise the two wheel speeds = 391

sounds good to me - its been many years since ive done all this - and to be honoust you will prob never need it again - typical schooling !

markk

iTrader: (2)

same answer pal - i just like to be technical !!

GARETH T

i didnt even notice you answered it,,,

and isnt d 1- pinion/output shaft as they could be looking for it all!

markk

iTrader: (2)

it is only pointing to the gear tho !

GARETH T

it does say "identify and name eash of the numbered components" and as the component is a output shaft incorperating pinion, i just thought i would say! and you know how funny college teachers are,,, unless you write down what they have on there piece of paper its a fail

M Brian

I didnt understand the calc where the 30 etc had came from?
is it simply
average of the 2 speeds and 376+406/2 = 391?

EDIT just read thats exactly what gareth did :cry:
they always did say fully read the question first pmsl

I typically look for a question more difficult than is there... takes me ages to go through simplish questions.. I was looking for final drive ratios etc to work back to mainshaft speeds etc.


oh and billy haynes where the pic is indentical to, item one is simply called the mainshaft! bit vague there I think

bassboy

cheers for the help peeps...sorry aint replied had 2 exams this week so been revising!

Auto one is on thursday now...

thank you all for your help...checking through the notes there are no notes or digrams given regarding the gearbox, or the final drive assembly...

it is a BEng degree im doing in Automotive Engineering Design...however the teacher is annoying as he VERY rarely puts up notes for us and the pics he uses in class are too much to draw in the tim ehe puts it up

i have some other questions if anyone is bored

bassboy

bassboy

BTW does anyone know where i can get a bit more of a detailed pic of the gearbox for question 1a? im sure there should be a picture as well but theres nothing on the paper

bassboy

bassboy

i found these 2 pics in a text book and wondering if they can be adapted to use for the 4speed constant mesh gearbox showing what i want it to?





cheers

bassboy

M Brian

old haynes manual

thats where they have got most of the pics from! lol

fiesta mk2 or escort mk4 books I used throughout my degree for pics lol

bassboy

excellent!! ill go dig up my haynes manual LOL

does anyone know anything about steering boxes?

questions states:

A steering gearbox has a force ratio of 7.75:1 if the driver applies a force of 18N with one hand on the steering wheel of 0.5m diameter, calculate the torque at the drop arm...

how do you go about with that question?

bassboy

M Brian

possibly you should do it radially....

but it will be basically force x distance to get the moment- then multipled up by the force.

quick calc 18 x 0.5 = 9Nm x 7.75 = 69.75 Nm of force at the arm

I think it will be slightly different as its angular movement but I can't remember the calc.

do you not have the IMECH members handbook? has loads of formulas in for this - I can't find mine at the moment as ive recently moved house.


have you done an ONC or HNC before this?

M Brian

sorry force by radius actually gives you the torque.

it would be the moment I think if it was linear.

calculation still stands just the terminology - hopefully someone else can verify what ive put.

markk

iTrader: (2)

them pics show it perfectly - the top pic and the bottom pic , just engage 4th gear the drive is shown perfectly

as for the steering melv has sorted that for ya pal !!

WWW.PASSIONFORD-SCHOOL.COM

bassboy

M Brian markk thank you sooooo much for this...appreciate it greatly...i know all of the hands on stuff...its the the fookin theory and the maths that fooks me up BIG style (should be comfortably retaking my tech maths module in summer PMSL)

also have what seems a VERY VERY challenging question regarding hp, fuel economy etc etc if any one can help? or do you just wnna see the hole paper LOL

bassboy

M Brian

I didnt think the top pic was right as it doesnt show constant mesh gears?

gearboxman

Q1A:
4th gear on a 4 speed box, simply connects input shaft to output shaft.
Line diagram is a straight line!

James

Melv, whats your degree in if you don't mind me asking?

looks pretty similair to what i was doing 12 months ago although it wasn't at degree level.

M Brian

Mechanical Engineering.

I did the majority of what is being asked above on my ONC though, the level of questions on this one isn't going into that much detail, probably because 'bassboys' course focus's on other things rather than the maths of it all.

i.e. with my degree the clutch question would of given the inner and outer diameters of the clutch and you woulda had to do some calculus to differiantite between to the 2 figures to work out the radius of gyration etc etc

James

cool, i'd like to do something like that one day, just it means moving for me or one hell of a road trip, iirc bristol was the closest place to do automotive engineering at degree level for me.