Steering for a 110cc 4-wheeler

How much does the car weigh, your numbers suggest hundreds of pounds.

@zander I imagine with the driving motor installed about 150lbs.  I can physically pick up the front end and put in on a block to test the motor for steering (which works fine as long as it is up on blocks). When completed I expect the total weight to be about 350 lbs (just a guess).  I can try to find out for sure total weight tomorrow.

@mscientist33 I don't have a clear understanding of the setup, but I do know that an electric motor has the most torque at stall so something doesn't make sense. In general, most steering assemblies require some kind of gearing as in worm gear or rack and pinion. Perhaps some pictures?

Posted by: @mscientist33

I have a 12v motor, 1/4 hp, 23amp, 41 rpm with 310in-lbs of torq.  Should this motor be enough to turn the front wheels? 

From my calculations I would like to see at least 500ms for 60degress. For 1 revolution that would be 3 secs. That would put 60sec/3 at 20rpm.  Is it feasible to say that if I use a 1:2 gear ratio I would get close to my 20 rpm and double my torque? Honestly I have no clue on how much torque it takes to turn the wheels and I don't know how to figure it out.  

I didn't see any background in your profile, but your username implies???  It could be Mathematical Scientist... or a tongue-in-cheek euphemism or a private joke.  However, it sounds like you know a lot of good fundamentals about engineering mechanics.  I'll start out with the easy one...

Turning Speed - Double checking your Math, it's correct.  41 rpm equates to turning 123 degrees in the 500 ms timeframe you desire.  Yes... you could add a 1:2 gear ratio and double the torque and half the speed to turning only 61.5 degrees in 500 ms.

BUT - Are your motor ratings above measured by you or on the motor label.  Do they give some testing standards (say... ASTM).  Point being... are they marketing BS numbers or real verifiable numbers?  If I were you, I would assume they're optimistic.  That the 41rpm is an unloaded speed and that at the rated 310 in-lbs, the speed will be a good deal less.  You may not want to use a 1:2 gear ratio, if you can get away with it.

Required Torque - Figuring it out is quite easy.  Do you have access to another 4 wheeler that hasn't been cut up (still has handlebars)?  If not, maybe a large pair of vice-grips?  Do you have fish-scale?  This illustrates how to get a real-world torque number for the conditions you desire. 

I dare say that if you haven't messed with the steering geometry, you'll find it can be turned with less than 20 in-lbs of torque.  The human body can't sustain high loads for long durations.  And the ATV manufacturer certainly wouldn't want a muscle-man requirement.  310 in-lbs should be far more than is necessary for normal circumstances.

BUT - Depending on your safety issues, you may want to test how much torque is required in non-normal circumstances... on various inclines, wheels in a ditch... etc.  

Posted by: @mscientist33

I have already tried to go directly from the motor shaft to the steering shaft.  It was like the motor just didn't have enough to start turning.

Only two answers come to my mind:

1. The motor isn't living up to its rated standards.  Faulty.
2. You didn't have enough batteries.  23 amps is a LOT of current and likely the start up current may be far higher than that.  You'd need at least a car battery or some Lithium based battery to supply that much current.  

That's all I got.

VBR,

Inq

@inq I didn't realize this was for an ATV.

In that case having ridden many miles on one I can tell you turning them at slow speed takes a lot of input force. I will be buying a new one in about 18 months and it will come with power steering since at 81 and a bad shoulder I now need help.

Traditionally that kind of system was always hydraulic, but my 7 ton truck and soon to be side by side ATV are both electric steer so it can be done, but I suspect there is much more to it than just connecting a motor to a pitman arm. In fact I will bet quite a bit my truck is still hydraulic but with an electric motor instead of a parasitic belt system. The ATV has to be electric since any parasitic belt system would make the steering subject to motor surge and be quite a handful.

@zander - I'm just guessing, but the "110cc 4wheeler" leads me to believe it is at least similar to a small ATV... and I've never been on or near one enough to know how hard they are to steer.  But, the method outlined will give @mscientist33 the torque requirements he needs to make a valid decision.

VBR,

Inq

@inq Some can be very hard to steer, others not so bad. A 110cc is indeed what I call a child's ATV and will not be nearly as hard to turn as a full size.

@inq

Posted by: @inq

Required Torque - Figuring it out is quite easy.  Do you have access to another 4 wheeler that hasn't been cut up (still has handlebars)?  If not, maybe a large pair of vice-grips?  Do you have fish-scale?  This illustrates how to get a real-world torque number for the conditions you desire. 

With (Length/Force) known units being most important for (Metric/Imperial) comparisons!

The name mscientist is just what I use since I have been called in my area "the mad scientist".  I am normally a software engineer/systems engineer by trade.  I am always tinkering and making stuff and doing so has gifted me the name from the community.

I do have a fish scale and a pair of vice grips.  I will give that a try.

As far as the motor specs, that is from the motor label. 

I have attached pictures of the work I have done on the shaft.  If I am to stay away from the 2:1 ration what would you recommend?  Disregard the potentiometer in the picture.  I will use it on the actual motor when I get a good design for servo motor conversion.  It actually did work on the shaft but it might be a better choice if I placed it on the motor.

Currently I am using a 12V 35 amp hr battery.  I am also using a KBBC-24 as a motor driver.  If the actual motor should have turned the shaft directly connected then maybe my KBBC-24 if affecting the motor dynamics.  The KBBC-24 does try to control acceleration deceleration among other things.  I have attached the datasheet for it and I am using it in the 12v configuration.  I do have a 5k ohm on the high and low pins where the pot is connected and I feed pwm in on the wiper line.  This seems to work okay.  I am using another kbbc-24 in a 24v configuration for the drive train.  It seems to work really well.

Posted by: @mscientist33

"the mad scientist"

I like it! 👍 

Jeeze... THAT'S A MOTOR (drive one).  For climbing trees, running over them or yanking them out of the ground!!!  Dealer's choice. 🤣 🤣 

Looking at the whole thing... that is far more stout than I was imagining.  Even the Honda things for tourist to rent to drive all around here don't have that stout of a frame.

Posted by: @mscientist33

I do have a fish scale and a pair of vice grips.  I will give that a try.

I have attached pictures of the work I have done on the shaft.  If I am to stay away from the 2:1 ration what would you recommend? 

I'd suggest doing the pull tests first, do the Math and get the torque required.  Get it while stationary and if you can do the same test while moving.  It will be far harder to pull when stationary, much easier if its rolling and turning.  Ever driven a big car without power steering?  Can't barely budge the steering if stopped... pretty easy while moving even one mi/hr. 

Either way, you're going to be a lot higher than the 20 in-lbs I was WAGging.  If the fish scale is maxed out trying to turn it, just get a longer arm (pipe over the vice grips).  I'm imaging you've got plenty of common sense (seeing your work) and know about cheater bars. 😆  Same principle... just longer "L".  Make sure to use the units you want: inches-pounds.

I would hope the number is less than 310 in-lbs.  310 in-lbs would be like having to pull 25 pounds on the handlebars.  I can't see customers tolerating that for just tooling around.   Let us know here what you get for any conditions you test.

The decisions will be your choice if the torque value is very high...

1. that the R/C steering doesn't work while stationary - which causes electronic problems down the road since you'll need to have some circuitry/logic that doesn't try to blow hundreds of amps through the motor and burn it up.
2. You put in a gear reduction and sacrifice turn rate...
3. Get a more powerful turning motor.

Posted by: @mscientist33

Currently I am using a 12V 35 amp hr battery.  I am also using a KBBC-24 as a motor driver. 

I'm not a electronic hardware guy, so I can't advice you on the motor driver.  But there are plenty of people here that are expert!  I've never used one bigger than a 3D printer uses... about the size of you thumbnail.  

• I'm first assuming the 35 amp-hr battery is just driving the steering???
• 35 amp-hrs sound about motorcycle battery size.  That number is only good for how long it will last under certain loading condition.  Ron's the expert on that stuff!
• You need to find Cold Cranking Amps... that's how much it will deliver (short-term) to the motor.
• I'd suggest just momentarily touch the battery lead directly to the motor... making sure nothing you want to keep is in the way if it jerks the ATV.  I suspect it should turn it smartly without the motor driver in-between.  This will also let you know if you need to dink with the motor driver.  I see it has plenty of options, but I did not see its max capabilities???  It may be limiting how much is getting to your motor.

Please let us know how it's going.  I'd like to really learn from your handling of such large currents/motors.  Definitely... next level, Mad Scientist stuff! 👍 👍 

VBR, 

Inq

Yes, the drive motor is running 24v.  It is a hoss of a motor.  It definitely has no problems moving this thing around.  Common sense is something nobody has ever said I had!! lol. Thanks!  I will get some testing done and see what I come up with.  In the mean time, I'm also playing/learning about gear trains, planetary  gearboxes etc.  I would have to say just the beginning of this little project I have soaked up a lot data.  Bills site has been amazing so far.

Initial current from the battery is 10.5 amp max.

@inq Couple things. Your picture is of a 4 seater ATV with a motor 9x the size of the OP unit. The battery type is tricky. While a starter type battery (those with the initials CCA or MCA or the word CRANK anywhere on the battery) will give you a lot of instantaneous current, the recovery time is long. Think of your car, it starts the car then recharges for at least 10's of minutes to hours. A battery without the initials and words mentioned is called a deep discharge battery and is the tyoe used in electric golf carts. That seems like a better match. The average golf course uses a Trojan T105, it is 6V and 225AH. The safe discharge state is 50% and for longer life 30%. Let's use 50% for now. That means 6V X (225AH/2) or 675 Watt Hours (really 675 VA hours but close enough)

Now your challenge is to determine your average watts for the steering motor and the watts output of the alternator. Simple math will tell you if you have enough alternator to get you hoe to connect to the recharger unless you install a HUGE alternator with it's attendant drag on horsepower. 

@mscientist33 First some administrivia. Use the reply link at the bottom when replying so that person gets notified if he/she is subscribed. BTW, the side panel has a bunch of links to educate you about how to use the forum.

As far as the 10.5A, that is true only for a specific load. A direct short for instance will result in a much larger number and it comes with a great fireworks display.

10.5 sounds suspiciously like the voltage of a depleted LiFePO4 battery or a totally dead FLA.

Posted by: @zander

Now your challenge is to determine your average watts for the steering motor and the watts output of the alternator. Simple math will tell you if you have enough alternator to get you hoe to connect to the recharger unless you install a HUGE alternator with it's attendant drag on horsepower. 

The 110cc motor was punted.  @mscientist33 's machine is totally electric.  There will be no alternator.  Just lots of batteries and lots of recharging.