Frex SimWheel

Hi
In my opinion the smal shaft must have a roller nuth.
Because, with the big pitch differince they get there force with a big i from the smal motor.
When the smal shaft have a lead ore acme screw with a pitch from around 1mm
it will easy puch the rollernut on the big shaft and rotate the steer,but when i am turning the steer
you puch ,lets see,the rollernut back.
The nut housing can,t go back because the nut from the leadscrew won,t get the smal shaft turning
because the pitch is to smal and you have friction ,it wil stay in lock
This can only be done with highlead screws (because there pitch)but wil have a lot of loss
and lose your big i .
The motor is direct driven on the shaft and makes more than 3000 rpm a leadscrew cant take these revs.
One the video you see that,s possible to rotate the big shaft without a steer
This is only possible with the big pitch difference when the nuts are non sliding types
The smal shaft must be in my opinion a roller type ,because the smal pitch (isn,t possible with a ballscrew so smal)
the revs they can make (5000 max)and they are much stronger than a ballscrew.
I understand that the guy from frex sed it,s highly efficient, only with ball and rollerscrews you stay above 90%
And it,s easy for zero backlash (more difficult with leadscrews)
I totaly agree it,s far more easy to make it direct driven with a big motor ,and you can allways make adjustable
steer clerence the same way they did on the big shaft,that way you can use a cheap leadscrew but keep in mind
you need a big pitch to avoid locking on the end plate,when turning the steer(with smal pitch the steer will stick)
you can find nice ones on http://www.roton.com
The thing i find interested for a simulator is :when you take a motor with a spurgear (for example) use it within 1 and 5 o clock
take a trapezediol 22x5 conect this on the spurgear shaft, take a rollerscrew say 20x5 conect this the same way
frex did and you have a mechanicly self locking device (the steer wil be the lever arm)but wil have a lot off loss
because the sliding nut
regards Ad

Both screws must be ball screw (they are nonself locking ! ). They use relatively low torque motor so there isnt big force. Both screws has ends in bearing so they can easily take it.
BTW i really dont get it what you exactly mean.

Hi Manbo
I did give a reaction to egoexpress ,he wasn,t sure the smal shaft needs a roller or ballscrew
When using a leadscrew with smal pitch it,s self locking(the mechanical brake for simulator),highlead screw arn,t self locking.


Reaction fore smal torque motor:you give a lot of force from your arms on the steer too
When you give a force from 25kg on a steer from 20cm whide
And the pitch from the shaft where the steer sits on is 50mm
you have a force from around 200kg
This is anufh fore breaking a ballscrew 8x2,5mm from cncworld.com
That,s why i think its a rollerscrew,have a smaller pitch (gives bigger reduction ,you can use smaller motor)
and a rollerscrew can handle more force .
regards Ad

@adgun,

I can understand what do you mean, but sometimes it looks like your messages are generated from translation machine! :lol:


Regards, Thanos

I,am sorry fore that Thanos.
Only ball and rollerscrews can make the big and smal shaft run free.
With a locking nut you can only rotate the shaft he sit's on.
So when i take the smal shaft and motor out ,and take fore example the known electric carjack.
and put this in place from the smal shaft.
Make from the wheel a lever arm with a travel from 1 til 4 o.clock
You have a full lock when power is off,fore a dof 2
Regards Ad

when a actuator with 10mm/sec speed puches a ballnut with 10 mm pitch you get 60 rpm

I try make some spread sheet with calculation. Please could someone check it if its correct ? THX

Hi Mambo
Your calculation is oke.
You only forget eff. ballscrews are 90/95% effective. (it's best to use 90%fore calculation/you will have more)
You got 2 ballscrews,you need to calculate this way
10nm. 90%eff=9nm furst shaft.
9nm. 90%eff=8.1nm second shaft
Your steer will be 81% effective
regards Ad

I use 0,96 (its on power calculation with 0,8 for motor)

tronicgr
I am new in this forum and first of all i am sorry for my bad english, i hope you understand me.
I am trying to build me own force feedback steering wheel, and i was looking for related info over the internet.
In this case, Frex SimWheel, i expose my point of view.
The mecanism seams to be like this:
As the the screw-ballnut system has a particular feature, BACKDRIVING: Normally, ball screws are used to
convert rotary motion into linear motion. Backdriving is the result of the load pushing axially on the screw
or nut to create rotary motion.All ball screws, due to their high efficiency, will backdrive. The resulting torque is known as
“backdriving torque” and is the torque required to hold a load in position.

The big screw-ballnut is to limits the rotation of the wheel, and the small screw-ballnut is for the feedback.
The small will drive the bigger one in all cases the motor is on because its axial truth is much bigger than
any man can reach, so it will produce a torque on the wheel.
The torque that any man could do on the wheel will cause an axial movement on the ballnut of the big
screw-ballnut. As the two ballnuts are fixed together the small ballnut will make rotate the small screw.

Another point of view is, think that the ballnut of the small screw is no backdriving but has a spring to
permit a diferencial rotation movement beetwen the two screw. By two encoders, one as we had seen in the big screw
and other inside the motor, we can apreciate this diference in movement. By software and electronic control
the motor rotation can follow this diference as minimun as posible.

Why so compliate (i dont get it from description ..) but main reason for two screws is that they need gearing. The thing that they can limit the rotation of the wheel is only bonus.
If you want build own FF wheel gearing is last thing to worry about.
First you need control it somehow.

Why building a control? Simply use the electronics of a commercial wheel, and attach it to your construction.

regards

Well yes but witch one ?
DFP would be nice but it calibrates 900°/200° so you need more mechanical stuff
DF GT dont calibrates only 900° witch is good but buy new wheel only to disassemble ..
G25 same as DF GT - but more expensive
Fanatec: --
and so far i dont speek about sensor, how will electronics of a commercial wheel respond to another gear ratio ? If i would use my own sensor how it will react ? If i dont know this i can chose right FF commercial wheel. So it isnt that simple (if i want 900° and optical sensor and not only replace gearing)
I want try in next few weeks build power source (i have all parts) ant i try to connect it to amplifier. If it will work i conect it to DFP electronic (only motor so i can see how it will behaviour).

Hi Mambo

You might need this: http://simprojects.nl/hacking_a_force_feedback_stick.htm

Or this: http://simprojects.nl/flight_yoke_FF_mechanics.htm

:brows:


Thanos

Yes but i am not electronic guy so i went almost plug and play way ( http://www.a-m-c.com/images/productpics/30a8.jpg ) but main problem is still optical senzor and hellish DFP calibration procedure
I can only hope that when you finis AMC motor motion-controller yours next project will be FF wheel

Hello, I'm new here. I found you guys by doing a search on the frex wheel internals. This thread is extremely informative, but I do have a question for the owners of this wheel. Would you know what the pitch is on the large screw? I would like to attempt to make a poor man's version of the wheel and I'm looking into the possibility of using a monocarrier, but unsure of the pitch to use. Any info would be greatly appreciated.

Thanks in advance.

You can choose it. You know how many rotation of wheel you want and you know how long this wheel will be. From that you get pitch. Try to find something litle bigger than what you calculate. Than you must find screw with smallest pitch as you can find. If you then type pitch of big and pitch of small screw into download/file.php?id=1565 you get power rating of motor (approximately).

Thank you sir.

I still dont understand how the small shaft vork with big that thevhole thing don't lock