Need to govern speed on a 24v system pocket bike

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Tom_in_AZ
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Need to govern speed on a 24v system pocket bike

Hello, first post here. I see most of you are trying to push your machines fast which is really cool, but I am trying to look at the flip side of things. I want to SLOW down a 24v Razor Mod Bistro scooter so I have no worries about my 5yr old riding it. It is a pretty good scale size next to him and Razor I feel missed their mark by now coming out with a 12v version of it.

I was told to put a variable resistor onto the red wire coming out of the twist throttle control. However I have also been told that this leads to heavy loads on the whole system.

Is there anything else that I can try, or swap parts out with that will fit in the stock setup? I'd like to be able to upgrade it back to the 24v system when my kid is ready for it.

Thanks guys,
Tom

goodnslo
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Re: Need to govern speed on a 24v system pocket bike

IF your controller is the same as the one I found on this page ( http://www.partsforscooters.com/119-36 ), the minimum operating voltage is 5v. I suggest reducing the voltage of your pack to 12v which will reduce the max rpm of the motor (i.e. speed of the scooter). Disconnect one battery.

This might reduce the range, unless you hook the batts in parallel, but make sure hooking in parallel should not exceed the max amps for the controller.

Reducing the volts brings up "how are you gonna charge it easily", and I dont have a quick solution for that unless you buy a 12v charger with the razor style connector.

chas_stevenson
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Re: Need to govern speed on a 24v system pocket bike

Tom,

First welcome to V is for Voltage, we have a great group here with lots of knowledge.

The variable resistor onto the red wire coming out of the twist throttle control is the easiest solution. You can place it in the wire where it connects to the controller so it will be under the body and you son can not turn it back to full power. This does NOT place any extra load on the system, all it does is regulate the throttle so full throttle can not be reached. Here is a picture which I hope will help.

      throttle_limiter.gif

Here's how it works. The voltage across the throttle is a very small amount of current because it is just a control signal of 5 volts. When the wiper arm ( <--- green wire) is moved up and down on the throttle the voltage on the green (center) wire changes from about 0 volts to about 5 volts. The closer to the red wire (top) the more voltage, the closer to the black wire (bottom) the less voltage. Adding the variable resistor to the red wire will move the 5 volt signal up higher on the circuit so the top of the throttle will now be something less than 5 volts. If you put a large resistance on the red wire you will make the controller think it is far from full throttle even when the throttle is twisted or pushed to the maximum setting. The best variable resistor size would be 5K or 10K ohms. You may have to adjust it several times to get the desired effect. Word of warning, even with this modification the scooter may still gain higher speeds over long straight runs, so keep him in the back yard or a close area.

Good luck,
Chas S.
My Bicycle Pages

jimby
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Re: Need to govern speed on a 24v system pocket bike

Hi,

I was attempting to do the same thing and came across your post, so that was great. I made the mod but couldn't perceive any noticeable change in max speed. This is with no load, on stand as I was testing it.

Even without a load I thought that since I was reducing the signal voltage I would still slow the revs as I turned the pot. It's a birthday present and they havent received it yet so I can't really try it out properly.

I used a 10K pot inline with red wire coming from throttle (not the red wire that comes out of connector).

Thanks in advance.
Jim

Fechter
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Re: Need to govern speed on a 24v system pocket bike

The input resistance of the controller is probably around 150k. Putting a 10k in series with the signal won't change the max output much.

Putting a resistor in series with the the +5v will work over a certain range, but when the hall effect chip in the throttle starts getting below a certain voltage, it stops working altogether.

A better approach might be to put a voltage divider on the output. You can adjust the maximum output anywhere from zero to normal.

Throttle_limiter.jpg

chas_stevenson
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Re: Need to govern speed on a 24v system pocket bike

Jim,

Remember you are not adjusting the voltage. The controller is still putting out full voltage but the over all current will be less. You must check it under load. When you test it on a stand the motor will still run as fast because the current requirements are low.

I was also looking at Fechter's post which may be another approach. I have not tried it so I don't know. I do know mine works but you have to test it under load.
Chas S.
My Bicycle Pages

aproldan
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Re: Need to govern speed on a 24v system pocket bike

i have another idea that would be much better then messing with the electronics and possibly hurting you mod.... why not just change the gearing in the rear... if it uses a 65tooth just put a 80 tooth back there and youjust cut down your speed by about 4mph and if you need to do the same for the front sprocket( this is assuming that the mod uses sprockets and not belt driven.... so you will still be using the 24volt system and will get longer riding time for you child... doing this will cut down on it's top speed and he/she will gain more torque.. and longer range... something to think about... later, armando/evpb30mphclub

armando/evpb30mphclub

magudaman
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Re: Need to govern speed on a 24v system pocket bike

Unless this is a really, really crappy motor controller putting a pot inline of the throttle out put should not hurt your run time in fact should increase it. Basically this just will limit how full of throttle it will let the controller go. If your range is decreasing feel your electronics for very hot things because that energy has to go somewhere but I highly doubt the controller could cause that much of a problem.

goodnslo
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Re: Need to govern speed on a 24v system pocket bike

i have another idea that would be much better then messing with the electronics and possibly hurting you mod.... why not just change the gearing in the rear... if it uses a 65tooth just put a 80 tooth back there and youjust cut down your speed by about 4mph and if you need to do the same for the front sprocket( this is assuming that the mod uses sprockets and not belt driven.... so you will still be using the 24volt system and will get longer riding time for you child... doing this will cut down on it's top speed and he/she will gain more torque.. and longer range... something to think about... later, armando/evpb30mphclub"

I would be careful of this solution because too much torque at low speed for inexperienced riders is just as bad as too much speed. You dont want the kid dropping the Pbike on himself/herself when it wheelies and jumps out of control.

jimby
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Re: Need to govern speed on a 24v system pocket bike

Hi there,

Thanks for all the replies.

I tried the 10K resistor as shown but it doesn't appear to have any effect on the speed. What would happen if it were placed in line on the green wire, would this have a similar effect.

I was going to try a larger POT, maybe 100K.

The voltage divider thing looks good also, so I may also try that if the 100K doesn't work.

Cheers
Jim

Tom_in_AZ
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Re: Need to govern speed on a 24v system pocket bike

:jawdrop: WOW, how in the world did I get unsubscribed from this thread? :jawdrop:

Man, thank you all for your help! I will get out to Radio Shack tomorrow to see about that 150k resistor. My kid is only 35lbs or so, and I can't see how he could cause the electronics to gather up that much heat. If it does seem to not be happy I will try the other solutions posted. I 'll also be sure to post back my findings.

I was actually hoping that there was a 12v system available that would have been a drop in replacement. I am rather surprised that Razor and the pocket bike companies do not offer them to get younger kids on their products.

So far the only mods I have completed to the Bistro is a set of training wheels on the rear, and I put inline a keyed switch with the fuse and it just hangs out the rear. Now he can't get on it and hurt himself till I can get it to run slower. When I get back in to the panels I'll put the fuse back to being direct and hook the key switch up to the wires going to the current rocker on-off switch. I will also be running some LEDs to 24v output to add a little extra realism for the kid.

On the resistors, will a micro pot do, or am I going to need a heavy duty 0.5watt style pot? I am guessing a micro pot would do fine since we are just adjusting a small signal to the circuit as opposed to something with a higher amp draw.

Thank you all again!
Tom

Fechter
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Re: Need to govern speed on a 24v system pocket bike

A micro pot will do. I like the 10 turn trimmers.

Tom_in_AZ
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Re: Need to govern speed on a 24v system pocket bike

Cool, got a good source for them?

Tom_in_AZ
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Re: Need to govern speed on a 24v system pocket bike

I found a bunch on Mouser's website, but they are 20-25turn pots, not a big deal, just means a better adjustment.
Here is a link to multi-turn pots: http://www.mouser.com/search/Refine.aspx?Ne=254016%2b1447464&N=1323038%2b254358&Ns=P_SField&RefType=Header

The order has been placed for both a 10k and a 100k so we will be able to test it both ways in case I do not like the outcome of the first. I ordered 3 of each, totaled out to about $11+ shipping.

Thanks everyone,
Tom

Tom_in_AZ
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Re: Need to govern speed on a 24v system pocket bike

I got the resistors in the mail, the bike is opened up and I have access to the wires.

Ok, so variable resistors have three legs. I am guessing that I would be taking one of the outer legs and soldering the green wire to it, then the other green wire goes to the center tap, followed with the ground going to the other outer leg. Its been a while for me here.
Thanks!
Tom

Fechter
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Re: Need to govern speed on a 24v system pocket bike

I'm not sure what colors your throttle is using. If the green wire is the signal, then your description sounds right. I would suggest testing with the wheel off the ground. There's not much risk of toasting anything if you get the wires wrong, but the wrong connection might make the motor stay on.

Drunkskunk
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Re: Need to govern speed on a 24v system pocket bike

How about a totaly diffrent direction? The hall effect throttle has to have a mechanical stop. something that keeps it from being twisted beyond full throttle. why not open up the throttle, and add some form of spacer, so the throttle can only.. for example, be turned to 2/3 throttle? It might even be possable to have this new stop be the end of a screw, so you can adjust it as needed.

if thats not posable, maybe it would be posable to move Sensor (POT or hall effect) so the trottle can never connect with full throttle.

I don't know how Razor does things, but the throttles I have worked with use +5volts is off, and the voltage goes down as the throttle increases. that way a shorted controller stops the motor. adding resistance to the system wouldn't change full throttle, but night mean it doesn't stop when you let go of the throttle.

jhfry
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Re: Need to govern speed on a 24v system pocket bike

Has anyone successfully speed limited a Razor PR200 or similar throttled bike/scooter. I have a 3 year old who loves motor cycles, and I can't see myself spending $150 for a cheap 2mph toy with hard plastic wheels that will fall apart within the year. I would much rather buy one of these, throw on some training wheels and speed limit it, and know that it will last him a few years and grow with him.

Oh and any hints about putting training wheels on one would be great too!

Thanks,

Joe

Deafscooter
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Re: Need to govern speed on a 24v system pocket bike

Deafscooter can do Reduce speed for little kids

But too late i have Major problem with Hacker

Im leave for business to closed my Deafscooter

Once because I got my wife filed Divorce Craig

Thank you for Asking me to do Modding throttle
Craig Uyeda
Deafscooter

deafscooter

jhfry
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Re: Need to govern speed on a 24v system pocket bike

Thank you for the response. I am comfortable with a soldering iron and am more than happy to do the work myself... I just need a simple schematic (or just a clear description) and a part list from someone who has done it and had it work well enough to keep a 3 year old safe and not ruin the bike.

Anyone?

mr_exon
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Re: Need to govern speed on a 24v system pocket bike

all I have to say is...if you think the bike is too fast for your kid, then dont let the lad ride it.

A five year old wold be a safer bet for teaching how to control a motorized bike.

if you still want to cut speed for your young child, then just add a 80tooth rear sprocket and take some air out of the tires...these two things will greatly reduce the top speed to less then 14mph at best. when you take just 10pounds of air out of the front and rear tire the bike will handle more sluggish so you child has more time to correct his mistakes before he goes out of controll and smacks the pavement....

governing speed through mechanics is by far more easy then doing it with the electronics

last, teach him how to ride with the right gear on, so if he does low side/high side he get as little hurt as possible.....

MiKeM
keep it simple ans safe and never go beyond your meens

I just Re-laced my first spoked wheel! and it was trued by spinning it in my hand

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