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SupportOld Support Forum Archive - Info OnlyMotorsGeared Motors up to 100WMFA Geared MotorsArchive through December 4, 2007
SupportOld Support Forum Archive - Info OnlyMotorsGeared Motors up to 100WMFA Geared MotorsArchive through December 4, 2007
Archive of the technobots.co.uk support forum
This copy of our old forum that closed to new posts in 2010. It is a 'work in progress' as we copy the pages across. The posts still provide a valuable source of information for both our customers and general info to the casual reader arriving here from search engines.
Archive through December 4, 2007
| Author | Message | ||
| Nponcele (Nponcele) Member Username: Nponcele Post Number: 1 Registered: 3-2007 |
Paul, I’ve been tempted into building a featherweight robot following some discussions with Rob (dangerous vegetable) at the Brighton modelworld exhibition this year. I have been looking at the new RE 975D motors with the 104:1 gearbox, and was wondering if you had some more technical data on them. In particular I’m interested in their weight and stall current, but if there is a datasheet with other details, that would be great. Kind regards Noel Poncelet |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 426 Registered: 10-2004 |
Noel, Nice to hear from you, hope you are well. These motors are not only new to Technobots but also new to MFA and data is limited. The weight is actually on the website under the product add to basket icon - 690g. Stall current is not published and I would not recommend stalling geared motors of ratios as high as this as damage to the gears is probable. This is why we publish the maximum momentary torque. If you need any further info, I will try and help. I could not Email you direct as you did not leave an Email address. Regards Paul |
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| Philip J Palmer (Sasquevaneach) Member Username: Sasquevaneach Post Number: 1 Registered: 5-2007 |
I recently bought a 30:1 MFA geared motor from you. It has stopped working. I have checked:- Wiring to motor. It is OK (it works the other one) The brushes look OK and are connected The motor turns, so it has not seized No obvious signs of burning out, damage etc It has only been connected to 8X 1.5 v AA batteries, nothing v powerful The capacitor looks Ok Other motor works fine, wired similarly (left & right motors in model) Worked fine previously, no obvious reason for stopping. Dones not spark when wired up, no apparent current. I don't have a voltmeter. Any ideas as to what is wrong? Phil Palmer |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 490 Registered: 10-2004 |
Phil, This is a surprise as we have sold thousands of the MFA motors and cannot recall a failure like this. There's always a first time I suppose. I would ask that you check the resistance across th motor terminals with it disconnected from the battery. If you don't have a meter, then you can of course return it but we would have to charge you carraige to return it back if no fault found. We are closing for two weeks so we are unable to check / replace until we re-open. If you cannot wait, you could contact MFA direct (you will find their details through a Google search) and mention you purchased the motor through us. they may insist that you return it to us but worth a try. Is there any smell from the motor? |
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| Tim Hill Unregistered guest |
Hi, I have an application for that needs a geared motor (something like the MFA 940D). However noise is potentially an issue, and I was wondering which is quieter, the orbital or metal geared motors? Cheers, Tim |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 592 Registered: 10-2004 |
Tim, Good question and one that we do not have figures for. I would however stab a guess that the orbital type are less noisy due to less friction parts but the motor itself will still generate a significant proportion of the noise emitted. |
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| Bob D Unregistered guest |
Hello Tech dept Just considering ordering a 941D Planetery Geared Motor but need to know if they can be used in either direction. Is it just a matter of reversing the posative and negative connections. Your help on this matter would be appreciated. |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 593 Registered: 10-2004 |
Hello Bob, All of our motors can be used in either direction and as you say, just swap the pos & neg over to the motor. |
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| Bob D Unregistered guest |
Hello Tech Dept Thanks for the reply to my last query regarding forward/reverse of your small motors. The next item I would need to find is a simple rocker type switch which when pressed one way will connect forward rotation and when pressed the other way will connect reverse and when released will be in the nuetral positions. Can you supply this type of switch. Any help on this matter would be appreciated. |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 595 Registered: 10-2004 |
Bob, We only supply this type of device for radio control use. You simply need a 3 position DPDT switch with centre off. Maplin Electronics would be your best bet for this. |
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| jonathan twiggs (Motorman) Member Username: Motorman Post Number: 1 Registered: 11-2007 |
Hello i have an enquirey about the 941D Planetary Gearbox 62:1 - Part No: 1450-071, also the 941D Planetary Gearbox 4:1 - Part No: 1450-070. My question is that if the ouput shaft was attached to say a gear, could drive be put back through the gearbox when power was off, (could rotation be applied to the output shaft that would in turn rotate the motor) Many thanks Jonathan Twiggs |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 632 Registered: 10-2004 |
Hello Jonathan, In theory yes but I would suggest there is a practical limit based on the reduction ratio. 4:1 no problem but 62:1 does concern me. Not having tried it on ratios above 11:1, there could be a risk of gearbox damage on the 62:1 depending on the torque attempting to turn the output shaft. You may find that the torque required to overcome the gearbox / motor losses may exceed that avaiolable from your drive train and in fact stall it. Also, what is controlling the motor and will it accept regen currents? Some motor controllers that use a relay to change motor direction will actually short out the motor when powered down. Others including 'H' bridge may not like having regen currents at all when powered down as it can pop MOSFET's. So no absolute answer but a 62:1 into a speed controller that has shorted out the motor when powered down is going to be a problem. Regards Paul |
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| jonathan twiggs (Motorman) Member Username: Motorman Post Number: 2 Registered: 11-2007 |
Hi paul, thanks for the reply, i will try to clarify, the motor will be in place to drive the ouput shaft then when the motor is off, the output shaft will rotate, and in doing so rotate the motor What is regen current? is that current that is induced in the motor as it is spun, if so could this be used to put power back into the batteries? Regards Jonathan |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 636 Registered: 10-2004 |
Hi Jonathan, Are you using a speed controller to drive the motor? When you say the motor is off, do you mean switched off using a switch between the motor and battery. Regen current is as you suggest where the motor becomes a generator and can in certain circumstances drive energy back into the battery. Doing so will put a load onto the motor which we call regen breaking. If you can give us some idea of what your set up is like, hopefully we can answer further. Regards Paul |
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| jonathan twiggs (Motorman) Member Username: Motorman Post Number: 3 Registered: 11-2007 |
Hi Paul It will be a simple battery to the motor set up with a switch in the middle to turn clockwise or anti. it will be attached at the output shaft and so when the motor is not electrically driving the shaft drive will occasionally come back through the system. what is regen breaking, is it very bad for a motor? Thanks Jonathan |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 638 Registered: 10-2004 |
Hi Jonathan, Regen breaking is generally good for applications such as electric vehicles. As I guess you will be using a DPDT switch with a centre off position, regen breaking will not be an issue as the motor windings will be open circuit when switched off. This means the only resistance to turning the motor from the output shaft is losses through the gearbox and motor. What I mentioned in my post 632 above still applies, 4:1 no problem, 62:1 still concerns me that the gearbox could become damaged but that is simply a gut feeling. Regards Paul |
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| jonathan twiggs (Motorman) Member Username: Motorman Post Number: 4 Registered: 11-2007 |
Paul would it be possible to use the power put back through the motor to put charge back into the batterys, thanks Jonathan |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 639 Registered: 10-2004 |
Jonathan, That's a good question and I have not seen it done with a reversing hardwired arrangement like yours. You could use 4 diodes across the DPDT switch which only conduct when the switch is off (centre position) and the motor is acting as a generator. The problem is voltage drop across the diodes will probably mean little or no current will flow to the battery. What you really need is one of our Dimension Engineering speed controllers which have regen breaking on them. |
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| jonathan twiggs (Motorman) Member Username: Motorman Post Number: 5 Registered: 11-2007 |
Hi Paul I see what your saying about the diodes taking most of the current, seeing as the turning motion going back throught the system will not be very quick and unconstant, then i guy regen is not really applicable. Thanks Jonathan |
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| Admin (Admin) Board Administrator Username: Admin Post Number: 642 Registered: 10-2004 |
Happy to help. |
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