Wheels for Model Size Motors

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Carl Westerling
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Posted on Thursday, March 6, 2008 - 12:19 pm:    Edit Post    Move Post (Moderator/Admin Only)

I'm a tech at a local girls' school & they are involved in a robotics project. It is suggested that we use RE 280/1 4mm Metal Gearbox 100:1 - Part No: 1450-043 for drive motors but which wheels are appropriate? They would like them about 65mm diameter so are the Solarbotics GMPW Plastic Blue Wheel - Part No: 4611-001 ok? If not, will you suggest which we should use from your catalogue.

Thank you, Carl Westerling.
Admin (Admin)
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Username: Admin

Post Number: 731
Registered: 10-2004
Posted on Friday, March 7, 2008 - 2:42 pm:    Edit Post    Move Post (Moderator/Admin Only)

Carl,

This is an area which we have not really managed to solve yet. The 4611-001 are not suitable as they are designed to fit the rectangular dive shaft of the GM2 & GM3 motors. The 4611-004 wheels are for the spline shaft on servos. The only wheels that are a tight push fit the the 4mm round shaft of the RE 280 is the MFA robotics wheel 4603-004 which is 79mm diameter.

Regards

Paul
Webbot (Webbot)
Member
Username: Webbot

Post Number: 7
Registered: 3-2008
Posted on Thursday, June 19, 2008 - 11:43 pm:    Edit Post    Move Post (Moderator/Admin Only)

Hi,
I have some geared motors with a 4mm output shaft. I'm trying to find some drive wheels (for a small robot - diameter of say 2 to 3 inches) that I can attach. Have trawled your site and FAQs but the only wheels that mention the bore/hub size tend to be 5mm. Other wheels don't mention the size of shaft. Sorry, if its a daft question - the 'mechanics' side is my weak point!
Admin (Admin)
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Username: Admin

Post Number: 820
Registered: 10-2004
Posted on Friday, June 20, 2008 - 3:56 pm:    Edit Post    Move Post (Moderator/Admin Only)

Hi,
This has been a problem for us for a while now. What we do have is some inserts that push into a 5mm hole and are suotable for 4mm shafts. The product is 4607-065. Most of our wheels are design for an interference (push) fit, these inserts allow for a far better fixing. An example of then in action is shown below.
Thomas walker
Unregistered guest
Posted on Friday, June 5, 2009 - 9:58 am:    Edit Post    Move Post (Moderator/Admin Only)

Hi

I bought a set of wheels of type:

EMG30 100mm Wheel with Hub - Part No: 4260-050

I mounted each wheel directly to the shaft of a motor, type:

MFA Como Drills 919D Series 4.5-15v DC (i had to bore out the wheel hole a touch).

However, I now find that for my mobile robot this direct mounting is not a good solution - the robot weight is such that the wheel needs to be supported from both ends, not just by the motor shaft.

I was hoping you might be able to suggest a solution. I was thinking of mounting the wheels separately and dirve them indirectly via steel gears. Perhaps you can suggest a set of parts? Idealy I would like to keep using the motors and wheels but would consider similar alternatives.

Thanks,

Tom
Admin (Admin)
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Username: Admin

Post Number: 1060
Registered: 10-2004
Posted on Monday, June 8, 2009 - 3:37 pm:    Edit Post    Move Post (Moderator/Admin Only)

Tom,

I would not recommend drilling out the EMG wheel to 6mm as this will make them too weak in my opinion. Depending the robot weight, a cantilevered wheel can put stresses on the motor shaft and output gears resulting in early failure. Two solutions, have the wheel 'simply' supported which means that the axle is supported on both sides with bearings. This means having the axle protrude all of the way through the wheel to another bearing block on the outside of the wheel. Motor shafts tend not to be that long so you need to extend them using a shaft coupling. Our discontinued featherweight robot kit had specially designed wheel hubs that had a protrusion on the outside that went straight into a bearing block - see http://www.technobots.co.uk/Data%20Sheets/7020-500.pdf for details.

You can do something similar to the above with the extra bearing block between the motor and wheel but the problems with the motor shaft length is the same.

Indirect drive is a common way of approaching the problem but all depends on the layout of your robot. Personally, I would have drilled the ENG wheel all the way through with a 5mm hole, used a length of silver steel bar and a pair of bearings, one either side of each wheel and used a chain, timing belt or gear drive from the motor shaft to the axle.
tom walker (Tomjwalker)
Member
Username: Tomjwalker

Post Number: 7
Registered: 9-2007
Posted on Monday, June 8, 2009 - 5:28 pm:    Edit Post    Move Post (Moderator/Admin Only)

Pdf looks like a good solution. I'm using only 2 motors with your MD22. Is there a 4 motor option for controlling forward+reverse of all four?

With just 2 wheels i think the hard EMG30 wheel is more suitable for carrying the robot's weight. I'm making progress with somthing like you indirect drive description, but I've pushed out the aluminium insert from the wheel rather than drilling a hole all the way through. I might be able to get away with not using roller bearings if the steel rod is suspended by a hard nilon like material (which is a natural bearing material). It's still WIP...
Admin (Admin)
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Username: Admin

Post Number: 1062
Registered: 10-2004
Posted on Monday, June 8, 2009 - 8:05 pm:    Edit Post    Move Post (Moderator/Admin Only)

A speed controller does not really know how many parallel motors it has connected to it. The Zeobot that was being described in the PDF worked with from 1 to 4 motors in parallel per channel. As long as the combined load of the motors is witin the rating of the controller then it's fine. The MD22 is rated at 5A so it is not really intended to run more than one 919D although many customers have when a heatsink was added. The limitation then is PCB tracks burning out. What weight is the robot and what ratio is the geared motor?
Admin (Admin)
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Username: Admin

Post Number: 1065
Registered: 10-2004
Posted on Tuesday, June 9, 2009 - 7:23 pm:    Edit Post    Move Post (Moderator/Admin Only)

Tom,

We have a new range of inserts 4604-051 launched today that will push into a 7.5mm hole in a plastic hub. The inserts come in a variety of bore sizes including 6mm and are made of brass. I pushed one into a 100mm wheel 4608-019 today and looks like a good solution. Push one into both sides, attach the motor to one side and insert a 6mm steel shaft through the other and you can support the wheel from both sides. The shaft can even partly enter the insert on the motor side for maximum rigidity. I shall experiment more and put some pics on the website or here on the forum as soon as I can but most likely not until next week.
Andrew Hough
Unregistered guest
Posted on Monday, April 19, 2010 - 12:52 pm:    Edit Post    Move Post (Moderator/Admin Only)

Hello,

I'm looking for a pair of wheels for a mobile robot. I'm currently using the Robot Electronics ones (Part No: 4260-050) but these have no grip and consequently slip on both wooden floors and on carpet.

Hence I am now looking at your rubber wheels (Part No: 4608-019) but have a few questions. They will be fitted to a robot with a maximum weight of 10kg. Are the wheels capable of taking this sort of weight without major deformation? Do the tyres have a tread or are they just smooth rubber? (The picture is not clear.)

Thanks in anticipation

Andrew Hough
Admin (Admin)
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Username: Admin

Post Number: 1237
Registered: 10-2004
Posted on Monday, April 19, 2010 - 4:35 pm:    Edit Post    Move Post (Moderator/Admin Only)

Andrew,

These wheels are intended for model aircraft. We have used this type of wheel in heavier robots but only after filling the tyre with a foam insert and replacing the hub. As standard, they are not suitable for 10kg, may be 1-2 kg max.