hello i am going to make a rack and pinion and would like to know how to calculate the turning dimensions so at about a 90-100 degree turn it would reach a max turning point of 2.5 cm left or right, i am looking at using a bicycle chain and sprocket as one.
Homemade rack Pinion
- Thread starter IKE323
- Start date
- Status
fowler
New member
what???
do u want to calculate the angle of the wheels for the angle of the steering wheel
the number of turns lock to lock
the reaction of the rack (how fast it turns)
what exactly
it appears u want to achieve a very accurate turn of some type
do u want to calculate the angle of the wheels for the angle of the steering wheel
the number of turns lock to lock
the reaction of the rack (how fast it turns)
what exactly
it appears u want to achieve a very accurate turn of some type
umm not thats what i am talking about, um i am thinking setting the steering wheel so that it at full lock eg to the left, the steering wheel is turned about 90-100 degrees and then the rack and pinion moves eg 2.5 cm to the left.
Ah I think I understand, you want to turn steering wheel and thus the pinion 90-100 degree and your rack should move 2.5cm, correct?
Well in that case it's easy as hell, the pinion circumference should be about 10cm (a quarter of that aka 90° would be 2.5cm) which will then end up in a pinion diameter of about 3.2cm ( 3.2 x Pi = ~10 )
'sid
PS That is a small bike sprocket you want to find there
[EDIT]
Oh I was a little late.. anyways that's still what I understand
Small movements like this should be accomplished with a simple pitman arm rather than a rack and pinion... but that's your choice
Well in that case it's easy as hell, the pinion circumference should be about 10cm (a quarter of that aka 90° would be 2.5cm) which will then end up in a pinion diameter of about 3.2cm ( 3.2 x Pi = ~10 )
'sid
PS That is a small bike sprocket you want to find there
[EDIT]
Oh I was a little late.. anyways that's still what I understand
Small movements like this should be accomplished with a simple pitman arm rather than a rack and pinion... but that's your choice
thanks man,so i need to get a diameter of about 3cm?Ah I think I understand, you want to turn steering wheel and thus the pinion 90-100 degree and your rack should move 2.5cm, correct?
Well in that case it's easy as hell, the pinion circumference should be about 10cm (a quarter of that aka 90° would be 2.5cm) which will then end up in a pinion diameter of about 3.2cm ( 3.2 x Pi = ~10 )
'sid
PS That is a small bike sprocket you want to find there
[EDIT]
Oh I was a little late.. anyways that's still what I understand
Small movements like this should be accomplished with a simple pitman arm rather than a rack and pinion... but that's your choice
sure, it's just the other way around;
mesure the diameter of the sprocket with 16 teeth (should have a diameter of ~6.7cm)
(6.7 x Pi = ~21cm) therefore a 90° turn would move the rack 5.3cm...
if you still want no more than 2.5cm you shouldn' turn the steering wheel more than 42°
'sid
mesure the diameter of the sprocket with 16 teeth (should have a diameter of ~6.7cm)
(6.7 x Pi = ~21cm) therefore a 90° turn would move the rack 5.3cm...
if you still want no more than 2.5cm you shouldn' turn the steering wheel more than 42°
'sid
fowler
New member
Ar righto
Itsid had it about right
To achieve this u will need to find the appropriate sized sprocket
This will be hard as u need a sprocket with a 3cm dia
The only other way to do this is to install a gear reduction in the steering shaft
Why such a tiny movement
Are u aware with this design of steering u are Likely to have 5mm of free play either way
I think this needs a rethink
Post some pics of the problem
Maybe putting more minds to it will help
Itsid had it about right
To achieve this u will need to find the appropriate sized sprocket
This will be hard as u need a sprocket with a 3cm dia
The only other way to do this is to install a gear reduction in the steering shaft
Why such a tiny movement
Are u aware with this design of steering u are Likely to have 5mm of free play either way
I think this needs a rethink
Post some pics of the problem
Maybe putting more minds to it will help
i am aware of this design as i am using quad a-arms mounted directly onto my kart and it need to turn 2.5cm to achieve a safe full lock turning.
I still see no reason why a pitman arm steering is impossible here...
The pitman arm should be about 3cm, (taking less space than a 16T bike sprocket)
a 90° turn is impossible by design,
the possible ~87° turn would move the tie rod about 99% of the arms length (measured from bolt to pivot that can be in the 2.5cm range)
*shrugs*
'sid
The pitman arm should be about 3cm, (taking less space than a 16T bike sprocket)
a 90° turn is impossible by design,
the possible ~87° turn would move the tie rod about 99% of the arms length (measured from bolt to pivot that can be in the 2.5cm range)
*shrugs*
'sid
fowler
New member
I used a cut down car rack with quad arms off a small quad
Works fine
It's far tighter than a home made one will ever be
Also the pinion is of course very small in dia to give good feel
I only needed an angle grinder and a welder to shorten the rack
Works fine
It's far tighter than a home made one will ever be
Also the pinion is of course very small in dia to give good feel
I only needed an angle grinder and a welder to shorten the rack
ok so do you say my pinion is correct or should i change it so that my steering wheel turns more?
Doc Sprocket
*********
I'm with Sid on this one. I really don't think it's worth all the difficulty involved in fabbing up a rack and pinion setup, in order to achieve 2 inches (2.5cm each direction) of total travel, and maybe 180* lock-to-lock at the steering wheel (~90* each way).
With a direct steer (what has been referred to above as "pitman arm") setup, steering wheel rotation will indeed be somewhat less than 90* in each direction, true- but achieving the small amount of tie rod travel (2.5cm) is no problem at all.
Generally speaking, the point of a rack and pinion (or any type of "geared" steering is to a)Reduce the amount of physical effort required to steer b)attain an amount of rod travel not feasibly attainable by direct steer c)reduce feedback at the steering wheel and d)decrease steering sensitivity.
With the small amount of steering wheel travel you are trying to achieve and the small amount of rod travel you need, most of the effort required is completely negated.
Can you do it? Sure. Is it worth the effort? I don't think so.
Poboy kartman
Senior Moments Member
Doc-
You got me thinking :more than 90° not possible? I gotta study on this. .....
You got me thinking :more than 90° not possible? I gotta study on this. .....
You could have a 90° angle but's that's not a good idea,
direct steering creates a dead spot, that you want to have OUTSIDE the steering angle.
therefore it's easiest to have a one hole arm.
If you use two holes, you can have a greater steering angle depending on the distance of the two holes.
the further they're apart the more likely it is to increase the angle beyond 90° in each direction. (diameter of the tie rod as a rule of thumb)
but doing this you will move the dead spot inward,
and you do not want go beyond that point when you race, since at speed there is almost no turning back.
Hard to explain (especially in a foreign language) If you want me to, I can make a short video of what I'm talking about tomorrow.
'sid
Doc Sprocket
*********
More like not practical, or feasible. I am talking about steering wheel rotation if that's not clear.
Poboy kartman
Senior Moments Member
Hey- Just got back from the Twilight zone. ..I was daydreaming about elliptical levers, multiple linkages and then it occurred to me-I saw the simple solution to a 360° steering. Then I realized what the real question was and the simple fact of your 90° statement was.
The short answer is that without gearing, the system is a 1:1 ratio.At 1:1 when the steering wheel is turned 90° so are the wheels. This is a simplification and probably not 100% correct, but the point is without a gear ratio change (regardless of how it is achieved) 90° is the max possible and the practical maybe less than half of that.
firemanjim
Just kartin' around....
Me personally, I like more of a 110-115`+ in steering sweep for a kart. Too short a swing, like 90`, to me detracts from steering feel and control. Turns are too crisp and at high speed, you can easily lose control. (Dont ask how i know).... at a 115` ,I get more control of how fast the wheels shift left or right. Forget about trying to make a rack n pinion. By a cheap used one off ebay or just stick with a pitman arm. You can adjust the steering sweep kinda by how long the pitman arm is and how much swing you can get. Make sense?
Poboy kartman
Senior Moments Member
Just to be sure-we are talking about 180° of steering wheel travel. So are you saying you prefer 220 -230°of steering wheel travel and how do you do this without a rack and pinion?
firemanjim
Just kartin' around....
No, i mean i only want my steering wheel to turn from like 9:30 tp 2:30 , full sweep. 90` would be more like 10:30 to 1:30 ....
You can do this with a pitman, but not as easy with a rack... rack is geared to make it easy to turn, and because of this, you get more like 3 1/2 to 4 1/2 turns lock to lock....
After re reading above comment, maybe i mmisunderstoodwhat was being ssaid about the 90` sweeps.... for a total of 180`..... thats 9 to 3..... too much movement for my taste....
sure, it's just the other way around;
mesure the diameter of the sprocket with 16 teeth (should have a diameter of ~6.7cm)
(6.7 x Pi = ~21cm) therefore a 90° turn would move the rack 5.3cm...
if you still want no more than 2.5cm you shouldn' turn the steering wheel more than 42°
'sid
Update for anyone interested in this kinda thing
for pinions and steering travels
180 degree : 3.18cm diameter pinion
200 degree : 2.86cm diameter pinion
and 220 degree : 2.6cm diameter pinion
Ill probably head down to statewide bearings in again LOL to get my rack and pinion
- Status