Drive unit for a cable mounted car

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi,

this might sound a bit odd but it will end up being associated with a boating project eventually. It'll help you think outside the box (possibly).

I want to create a small lightweight drive unit to travel along and up an inclined wire, it's to be r/c controlled and will carry suspended beneath it a 'cable car' like structure [actually to be a boat]. This was the easy bit. The car/boat is about 30cm long, so the drive unit should be about 15 to 20cm long at most. It will be connected to the receiver and battery system already in the car, so will only entail an ESC and motor (280/360?) as drive.

I do not have the room to instal an endless looped cable system as used up ski slopes. This will be a single line, tensioned to take the load (hopefully) and the unit needs to be able to drive up a gradient of 6 feet in a distance of about 60. Weight carried is 300g + drive unit. It could be done with a pull string and that will be my fall back, but was hoping to do it by r/c if possible, as other functions have been built in and work.

Propellers are not permitted nor are jet engines, silent running as far as possible. The drive unit will not be in water, unless the wire breaks, and I can create a lightweight shield about it once it works.

I've an idea or two and will add them later, but knowing you all and your joy at suggesting fixes to all things I thought I'd give you the chance. Cut-off is 2 weeks away for an up and running unit. I have motors, ESC and such, its just the design of a drive unit to grip the wire/line etc.

Many thanks all, Kim

Edited By Kimosubby Shipyards on 12/01/2015 10:36:07

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

ideas sought

[ashley needhamParticipant @ashleyneedham69188]

I was thinking along the lines of the wire feed unit on a MIg welder….the wire passes over a powered wheel (could be a rubber faced cylinder in your case, driven by a gear system) and on top of the wire is a spring loaded roller, so apply sufficient pressure do thet the wire is gripped and fed on by the drum.

essentially, the driven wheel (or wheels) could be on top so the weight of the unit assists traction, and a spring or otherwise loaded (set/grub screw affair) roller underneath keeps the pressure on. You dont say how thick the wire is, Meccano wheels may do?? convenient bore sizes and very strong with a convenient groove around the rim (the ones that are made for tyres)..In factm, the whole thing could be meccano !!! easy peasy, no fabricating just bolting together and arranging the drive to the wheels.

Ash

[Malcolm FraryParticipant @malcolmfrary95515]

A butchered servo should provide plenty of drive, if not much speed. To get enough grip on a line at a gradient of 1 in 10, it will need some sort of rubber tyre and a tensioning wheel. With railways, 1 in 10 is in the beginning of needing a rack to ensure traction. Cableways that run on steep gradients are usually cable hauled because of the difficulty getting enough grip on a steep incline.

[shipwrightParticipant @shipwright]

Hello Kimo,

Interesting project. Clarification of requirement please :

a. Diameter of wire ? Is it actually wire or other material ?

b. Does the drive mechanism have to be contained within the load carrying box or could it be external with the box suspended from the drive system ?

Ian

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi All,

thanks for the keen interest already.

Drafted a very quick diagram of my thoughts, as below.

The drive unit hangs from the wire, via the two upper wheels , which also assist to force the wire over the middle drive wheel, which could be adjustable.

Ashley: Meccano sounds to be an ideal material to trial simple designs to get to a working unit. It would probably be too heavy on its own, I anticipate using plasticard in the final unit.

Malcom: Have re-checked the gradient, it's more like 3 feet in 60, but the unit weight would also create localised gradient at the point of contact, so you may be correct and I find that this is not doable for that reason, and lack of grip.

Shipwright: Wire possibly 60lb fishing line (1.2mm dia) or polyester three ply net making line (3mm dia) or other. I shall try and keep the line larger for more surface area contact. It will not be wire as such (yet).

The drive mechanism is suspended from the wire and the load suspend from the drive unit. Current thought is that the drive unit will have an ESC and its own small power unit (battery) whilst the receiver is with the load. This could well change when or if it works as the load will require to be detachable at some point. It might then be a garage door fob for the drive unit up/stop/down and release (my HK unit has 4 buttons) leaving the receiver to run the load when launched!

Would two drive wheels give better traction? Would they belt drive or gear drive?

Aye, Kim

[Paul TParticipant @pault84577]

Kim

12v High torque, low speed geared motor, such as used in robotics very compact and very powerful

Size 82x32x27mm

Paul

Edited By Paul T on 12/01/2015 14:01:05

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi Paul,

actually have one of these motors but they are quite heavy. At present I think my problem is getting the drive through the wheel to the wire. I'll crawl into my freezing attic workshop and try a couple of set-ups. By the time I look here again Ashley will have built a complete ski lift for me capable of climbing a 1 in 5 gradient!

Had some real weather this w/e and lots more to come too. Glad I'm not traveling anywhere till Easter time.

Aye, Kim

[Paul TParticipant @pault84577]

Hi Kim

You might be better biting the bullet and opting for stainless steel wire instead of polyester as the wire will provide better traction for the drive wheel.

To provide wheel grip you could use a simple spring load guide wheel or twin clamp style wheels.

You have some real nasty weather coming.

Paul

[Bob Abell 2Participant @bobabell2]

Kimmo

If you are only using fishing line, you could wrap it round the motor drive drum, several times for a really tight grip

Bob

[ashley needhamParticipant @ashleyneedham69188]

kimmo. see hobbies http://www.hobby.uk.com they do a pair of plastic gearbox brackets and also pully wheels also a work drive….worm push fit for 2mm ie a speed 280 motor….sprockets and chan to connect all 3 wheels together for grip.

Nylon line very strechy possibly coated steel wire… shark trace or something ??

Ashley

[Colin BishopModerator @colinbishop34627]

How about the wire used for model aircraft control lines?

Colin

[Trevor HollowayParticipant @trevorholloway99134]

Seems a bit late to suggest a high torque, servo drum winch with the wire wound round a couple of times for grip.

I'm guessing the turn rate would be proportional to the stick throw so would have in built speed control.

[Trevor HollowayParticipant @trevorholloway99134]

One like this but with a drum / pulley : **LINK**

[CookieOldParticipant @cookieold]

Hi Kim , Hope you are well ( seems ages since Haydock ) instead for useing standard fishing line which as Ashley says is very strechy there is something called fishing braid that is still as flexable as standard line but does not strech , It is available from all angling shops in plenty of diameters . It also is not as smooth as standard line so you would get getter grip on the drive wheels.

Best Regards Cookie

[Dave MilbournParticipant @davemilbourn48782]

Posted by Trevor Holloway on 12/01/2015 18:04:35:

One like this but with a drum / pulley : **LINK**

At first sight I thought that would be a damned good idea but then I saw that the thing only does 0.17 -0.21RPM. Either that's a typo or we're talking seriously slow (5 minutes to go round once??).
This is more like it http://www.servoshop.co.uk/index.php?pid=HITECHSR1425CR&area=Servo

DM

Edited By Dave Milbourn on 13/01/2015 09:53:17

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi All,

thanks for the interest and suggestions, it's a great help having others outside the box with me!

Colin: I have no familiarity with this line, so will contact the local flyers over here and see if I can sample some. Thanks.

Trevor: Brilliant idea, hadn't thought of a continuous servo. Have to agree with DM though, this one is very slow but the idea will be followed up.

Cookie: Hi again, I've considered braid fishing line, trouble is the cost when you want thicker line, very expensive, but I'll see my mate who's into fishing and see if he's some old stuff on a boat reel. I am considering washing line, or paracord (7mm) which is braid construction and I can get 40m for £10 delivered here.

DM: Now that servo looks the ticket, and I can see other uses for it. I can bolt a gear/pulley to the servo disc and marry up to the drive wheel no problem. The drive wheel BTW is 60mm dia. The speed at 4.8V should be enough so only need one battery and use magnetic contacts that will give way when the payload is delivered?

Thanks for all your interest, I'll keep you up to date with progress – so far I've just made the supported beam for the travelling pulleys and am about to weld on down struts to take the motor/drive train. Aye, weld with that Swedish Aluminium solder, knew I'd have a use for it.

Aye, Kimmo

[CookieOldParticipant @cookieold]

DM , Thanks for that link , thats just what i needed for another project.

Dave

[Malcolm FraryParticipant @malcolmfrary95515]

I think I mentioned a butchered servo in an earlier post.

A standard servo consists of a motor, a gearbox, a position sensor to tell it where it should think it is, and electronics to compare the known position with the proposed one. Mechanically unhitching the position sensing pot gives a motor/gearbox/control combo that, if the stop lug is removed from the output gear, will rotate until either it wears out or you tell it to stop.

With a 1/2" drum, there is enough power to pull in a 600 sq in sail on a one metre boat in any conditions reasonably quickly, probably 3 or 4 inches per second. Obviously, a ball-raced servo would have a better life expectancy.

If the original electronics have too narrow a deadband, a small ESC can be substituted. For a standard servo on 4,8v, an ACTion Pico is good, for more volts and/or current, one from MrRCWorld is OK but needs a separate BEC. Then at a silly low price there are the ultra cheap "10A" ESCs from fleabay. These have a BEC built in and are surprisingly effective as a winch control.

[Andy CParticipant @andyc56856]

Hi Kimmo

How about something like this. **LINK**

Should be easy enough to build. Even has room for control stuff.

Andy

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Me again.

Malcolm: Yes a butchered servo might have worked but I need a bit of power and some speed. Estimate at full speed the servo suggested by DM would do about 10m/minute on a 6cm drive wheel..

Andy C: very nice neat set up shown but it's not possible to set up a box sectioned track with a toothed belt drive as shown. I want a single line erected quickly and a drive unit to clip on easily and go.

Now that the severe gales have blown through (only 98mph this time – we had 103 at Hailwood Heights last time and then the instrument bust) and the boat's running again I might get some gear through. Island life, and some people were worried that their potatoes might not get through – image that. And as to two days without newspapers – well Armageddon better watch out.

Aye, Kim

[Malcolm FraryParticipant @malcolmfrary95515]

The only fast cableways that I can recall were in the old Co-Op emporium, mysterious things slung across the ceiling to carry your money one way and your change and divi chit the other. I feel that high speed and cables don't go together comfortably, but to shift a reasonable load, the three wheel design hooked to a gearbox with enough motor would work, especially if the driven wheel had a rubber band sitting in the bottom of its groove to give it more grip.

To quote Derek Warwick, after he totalled his car in practice "Its just a question of time and money".

[Trevor HollowayParticipant @trevorholloway99134]

They use the single cableway with powered car when dragging the logs up the side of the mountains in "Ax Men" – probably not along UK Elf and Safety requirements.

[Geoff SleathParticipant @geoffsleath41411]

Your system of 3 pulleys to grip the rope looks good. I would be inclined to make them so close the almost touch and make the single pulley spring loaded.

When we were sailing dinghies we used to use Kevlar spinnaker sheets which were non-stretch. Some thin Kevlar line may be available which you could keep at a very high tension to limit sag. It would also provide a better grip for your pulleys. I'm sure there are chandlers all over the Island who stock suitable line for dinghy sailing.

As to the weather in your neck of the Irish Sea. I remember an exciting trip back from the Manx Grand Prix. We were on Manxmaid (car ferry) in Douglas harbour and watched one of the old ships (King Orry?) going out stern first. I have never seen a ship roll so much. She was on her beam ends from side to side. It was very, very blowy and we accompanied the smaller ship all the way into the Mersey, I assume in case anything went seriously wrong. I sat on the deck, eating my sandwiches wearing all my motor cycle gear including helmet and goggles. Fortunately I have a cast-iron stomach and need serious conditions on a yacht before I'm throwing up.

I met someone on the way to the TT the following year who had been on board the King Orry and he told me that not a bit of crockery survived the journey unscathed. I think even I would have been uncomfortable.

Good luck with your project … and the weather!

Geoff

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi Geoff,

just no comparison today with yesterday's wind.

I've done the 16 hour journey from L'pool to Douglas on the old Ben, saw Peel 3 times before we got in. It's just something we live with, as do all islanders everywhere.

Still no servos arrived, but there is a big backlog of goods to bring in, so maybe tomorrow. Once I've cobbled a unit I'll pop over to Peel marina chandlers and see what they have to offer, though kevlar can create a hole in a pocket quite quickly.

Kimmo.

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