Hi ,
I have been wanting to model a full automotive 5 speed gear box in CATIA and I have done alot of reasearch into it. However I have come across a few problems:
If any of you could please help me that would be greatly appreciated
regards
Yohann
Hi Yohann,
There is plenty of info regarding the first 2 points here:
https://khkgears.net/new/gear_knowledge/
Be more clear or specific on your 3rd point.
Hello Yohann,
here is a model of a 6-speed transmission:
And here is a housing model for it:
If you are really interested in transmissions and the calculations round about it, I can recommend you this book:
https://www.amazon.de/Automotive-Transmissions-Fundamentals-Selection-Application/dp/3642162134
BR,
Alex
Very good homepage!
HI there,
Thanks for your quick reply. To clarify I want to design a 5 speed transmissison, i have spent countless hours trying to find data on the gears and the only thing I have manged to get is the gear ratios. This is great but from this data I am unable to work out any of the other data that I need such as the gear Module, gear diameters, pitch circle ECT. I thought I would be able to find a document of some sort that would explain from start to finish the process with mathmatical equatios what is going on in the design process. I am an engineering student so I am comfortable with the maths side with it.
Regards
Yohann
Thank you for your kind words.
Your page is amazing as well. I am trying to make a simmilar transmission as the one posted on your page. I have seen that you have done calculations from the screen shot of excel. How and what have you done. could you please explain if you don't mind.
Regards
Yohann
If you need gear data: You have managed out the ratios for your gearbox. If you now assume an center distance between the shafts, you automatically get all the pitch diameters (there are geometrically defined). By having gear ratios and pitch diameters you can calculate the rest of the gear geometry based on your experience.
If you dont't know the common values of center distances or modules:
Look at some knows transmissions and measure it. It doesn't matter if you start your gearbox with a=75mm or a=95mm or if your module is m=2mm or m=3mm, you will do the same calculation with the values.
You just need to start and don't give up if you stuck with some problems - Imporividsation will help you!
HI there
Thanks for your quick reply, you are the only person on the internet to give me a straight answer.
I love this group.
Regards
Yohann
Hi there,
I have been pondering on what you have last sent to me. I understand the approach you have taken however I have a question:
1. I know that the ratio of the pitch diameters is equivalent to the gear ratio therefore by using the data and an estimate of the distance between centres of shafts it will result in an equal pitch radius. Therefore, how would I relate this to the gears themselves since it would only work for the 4th gear since it would be 1:1 and 5th would be overdrive. While all the prior gears (1st, 2nd and 3rd) would all be 1:1 ratio as well making no sense. In other words, how do you split the pitch diameter of each gear based on the ratios.
Sorry to ask you so many questions but making the model is only half what I want to get out of this, understanding how a transmission is designed is the main goal.
Regards
Yohann
Think about how a center distance is defined and how the ratio ist define both by using pitch diameters :
a=1/2•(d1+d2)
i=d2/d1
Assuming the the center distance is all you need to find out the pitch diameters since you know you ratios ;-)
Hi there,
I have looked at what you have sent me with the formulas and i have created a spreadsheet to try and work it out.
I am confused as rearanging the formula "I" it will result in you needing D1 to work out D2 and D2 to work out D1. What am i Missing out.
Yohann, you're so close to the solution - You've got 2 equatiins and 2 unknown parameters to calculate. Should work out well, doesn't it? :)
Hi,
I realised just now that you could use simultanious equations to solve this. I have now calculated the values do you think they look correct??
You only mistake is that you devide the center distance by 2... Why? The center distance IS A = 70 mm. Therefore you have to double all your pitch diameters to be correct!
Keep going :)
Oh, by the way... Your 5-speed transmission is a classic standard transmission with a countershaft,isn't it?
Then the ratio of the gearbox is always achieved by 2 gearstages, the constant ratio down to the countershaft which is common for every gear and the gear ratio itself. The direct gear with rmthe ratio 1 of course doesn't use the constant as you connect inputs haft and output shaft.
Are you familiar with it?
Hi,
Yeh I am familiar with how the transmission works. However regarding gears which one will go on the countershaft and which one will go on the main shaft (input and output).
You can't double the values for D1 and d2 otherwise the diameter will be way to big. For example the first gear (55*2=110) and 110 is bigger than the distance between the shafts in the first place.??
Of course you can double it :) the center distance is the half of 110 mm plus the half of 30 mm which is 70 mm.
Try looking at:
http://thecatalystis.com/gears/
Super easy to use to visualize the end result of different gearing configurations.
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