Hi Core People
I fly gliders for a sport. The gliders are stored in hangar. To avoid damage when moving the glider in and out of the hangar, the glider main wheel is rolled onto a trolley and the trolley runs on rails into the hangar. The gliders weigh 250-750kg. Some of our members are over 70yo and/or have some disability that prevents them pushing the glider in and out of the hangar. So I thought I could make them a small motor drive to power the trolley along the rails. I am a mechanical engineer so the mechanical bits I am fine with. My efforts to date have got very close but I have trouble with the electronics. I am hoping you guys can assist!
The criteria is as follows:
- Torque at the shaft: at least 10Nm
- Rotational speed of the shaft: variable from 150-300rpm (but once set, will rarely be changed)
- Drive shaft dia: not relevant as I can machine up a coupling
- Control: ideally via a small wireless fob like a garage control so they can stand at the wing tip to guide it and control the trolley which is at the fuselage about 12m away. A cable would be problematic but not a showstopper.
- Start/Stop Control: must have a dead man function so push to operate, lift to stop in awe the guy drops the remote.
- Direction: must be bi-directional to move the glider into and out of the hangar.
- Soft Start/Stop: ideally (not essential) the trolley would accelerate to full speed at an adjustable rate to prevent excessive jerky movements. Once the rate is set, it would rarely be changed.
- Power: we have redundant 12V 8Ah SLA security system size batteries that we used to use in the aircraft that we could use in 12V or 24V configuration. We could go to 36 and 48V if needed but they would chew up a bit of space. We would want some means of charging the batteries insitu.
- Duty cycle: gliders get used about four days per month for six months of the year. The travel time from inside to outside the hangar is approximately 20-30seconds, twice per day so definitely not onerous.
- Size: The ground clearance from the centre of the drive shaft to the concrete is 36mm.
- Drive Train: a direct drive is preferred for simplicity. Chain and sprockets are definitely doable but more work involved.
Cost: my research to date suggests <$250 in materials is doable but I haven’t landed a solution yet so it may be more! The clever bit is doing it cheaply. Some of our members are retired so cost is an issue. I am happy to build this for them if I could get some guidance on the electronics tech bits.
There are things that could be adapted such as a 4WD cable winch that has a remote control fob but the speeds are too slow and the noise from the gearbox is horrendous.
I hope some of the very clever people that work for Core or are on this forum can help.
Note that I am not an electronics wizz so I’d be grateful if any responses could be in layman’s terms.
Thank you
Kel
Hi Kel,
Welcome to the forum 
Sorry for the delay getting back to you. I’ve had a look through our range and I don’t think we stock anything with a torque output above 1Nm. The simple reason for this is that once you get into higher power electromechanical devices there are some real risks to inexperienced users and most of our customers are home hobbyists and schools.
You’ll need a more industrial focussed supplier to find a motor with an output power great enough to do the work you need.
I can understand your hesitation to use a 4WD cable winch because of the speed and noise but given they represent around 90% of your requirements modifying a cable winch to use a different gearbox might be the best way to get the outcome you want without having to build an entirely new bespoke product with all the complexity involved.
Would swapping to a different gearbox with less gear reduction also reduce the amount of noise it makes?
Thanks for getting back to me Trent. I can certainly adapt something but I was hoping to find it in one package. If I found the right motor and gearbox combo or modified one to suit, can you help with the control piece and the remote fob?
Kel
| Trent
1 September |
Hi Kel,
Welcome to the forum
Sorry for the delay getting back to you. I’ve had a look through our range and I don’t think we stock anything with a torque output above 1Nm. The simple reason for this is that once you get into higher power electromechanical devices there are some real risks to inexperienced users and most of our customers are home hobbyists and schools.
You’ll need a more industrial focussed supplier to find a motor with an output power great enough to do the work you need.
I can understand your hesitation to use a 4WD cable winch because of the speed and noise but given they represent around 90% of your requirements modifying a cable winch to use a different gearbox might be the best way to get the outcome you want without having to build an entirely new bespoke product with all the complexity involved.
Would swapping to a different gearbox with less gear reduction also reduce the amount of noise it makes?
No worries, we should be able to help with that.
How failure-proof you want the dead man’s switch to be will be a large factor here with anything wireless.
I think the safest solutions in order are:
A long wire,
An IR remote like your TV would use,
Any other RF wireless protocol.
The issue with a wireless dead man’s switch is that it’s normal for there to be pauses between when commands are received in a wireless system. So the system has to make an assumption in the meantime that everything is still ok.
You could have a system check every half-second if the button is still pressed and shutdown if you don’t receive the “OK to keep running” signal, but it’s not quite the same as a physically hard-wired switch which interrupts power to the system.
Hi Kel
That is not going to give you a very big motor for direct drive so you may have to rethink your drive arrangement a bit.
The only suggestion I could make is to go to your local Golf Club. There may be some old battery golf buggies around beyond economical repair which you could get the motors and gear boxes to play with. They are usually quite robust.
I have a couple here which I just measured up. These have a body length of 105mm and diameter of 75mm, shaft diameter about 12mm. These were fitted to a worm drive gear box to drive the wheels, the final torque unknown so would be a trial and error thing unless you could measure it. The shaft has the worm part of the gear box as part of the shaft.
I had 2 of these coupled together to test buggy speed controllers under actual conditions. Coupled together, one as a motor and one as a generator which I could load up with lamp globes to provide the controller with an actual load. I haven’t used this set up for some time now but I think (pretty sure) I have the gear boxes floating around under the house somewhere. I live on the Central Coast, NSW so if you are anywhere near here you are quite welcome to them if you can pick them up and have a play. They are 12V brushed motors so quite easy to control speed.
Cheers Bob
Your 8 AHr might be a bit light on so you could run multiple batteries in parallel. Don’t know what the operating A would be as as you must realise this varies with load but the stall current is 23 to 25A.
Is tis proposal using an endless cable to pull the trolley to and fro or is the motor mounted on the trolley. I would think whatever method the battery(ies) would have to reside with the motor as utilising a retractible power cable would be a bit awkward.
Cheers Bob
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Cheers Bob, thank you for your reply and kind offer. Apologies for my tardy reply, I have managed to dodge the Rona…until now, so have been off the pace a bit but coming good after a couple of days.
You are right, any form of cable whether it’s doing the pulling or providing the power is not ideal. I am isolating up at the club (out of necessity) so won’t be back your way for a couple of weeks at least. If you can do without one of the motors, I’ll come and grab it and have a play with it. I could easily accommodate 4 x 12V8Ah batteries on the trolley so 48V is doable. I did think of putting two motors on each end of the trolley shaft, one spinning in opposite direction to the other to deal with the torque. Would that work?
I’m not sure how you deal with maintaining privacy when giving out contact details on these forums, but happy to exchange numbers however that can be done. I’ll be well past iso stage before I make any plan to visit!
Thanks again Bob
Kel
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Given your advice below, I am having second thoughts about the remote option. The issue is not personal safety but property safety. These gliders can cost a bit if damaged, like orders of magnitude bigger than the cost of the project. I retractable control cable could work that would wind itself back up to the trolley when not in use. That then solves a whole bunch of issues. Just need to find a retracting control cable device. Any ideas for that?
Thanks for your counsel on this. Much appreciated.
Cheers
Kel
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Hi Kel
You can have both and I will see if I can round up the gear boxes over the next few days.
These motors are 12V so you would connect the batteries in parallel to get a potential 32AHr (not 48V)
Due to medical appointments etc I will be out every day next week until Friday anyway.
This forum has a private messaging system which I have used before so I will see if I can figure out how to do it again.
Think I have got it. Will give it a go now.
Cheers Bob
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Hi Kel and Bob,
This is a good precaution to take since this forum is public-facing on the internet, you can send a private message to a forum user by clicking on their name or profile image then selecting message on the top right of the pop-up box.
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Hi Trent
Thanks. Got that. I have done this before, some time ago now, but it all came back to me.
Had a senior moment for a bit but all went successfully.
Cheers Bob
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