Drive unit for a cable mounted car

[TelstarParticipant @telstar]

Hi For non stretch cord try looking on Kite flying websites, I know that serious kite flyers use a non stretch very strong cord but I'm not sure what it is

Cheers Tom

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi Tom,

thanks for suggestion, might be a bit thin, I do use it for yacht sheets too.

Yesterday – bad news – built the first prototype as per my original plans, the drive wheel being directly connected to the drive servo and positioned under the support cable. Hung it on the wire and although the pulley went round, no grip or drive. Added to that, with the two additional wheels on top the cable the whole thing wanted to flip over. Doom and gloom.

So had a look on internet for cable car drive units and this turned up, created by children and it works! The drive on this is above the cable, but it uses 'elastic band' belt drive and was supporting 1Kg weight. There's more on http://www.kidsinventindia.com so inspiration at last. If they can do it so can I.

Design idea came to me during the night, two pulleys on the cable, everything suspended below, and the drive up to one (or both) pulley using a rubber band. To set the drive on the cable the mounting pulleys were diametrically positioned on their support beams, so that the assembly could be pushed up around the cable then twisted enabling the wheels to centre on it. Only one pulley drives at present, but there is a drive pulley mounted on both.

First run – slippage but foreword movement. Added a small tight fitting elastic band to the drive pulley. Tried again – eureka (as Bob would have it). It travelled at full speed up the cable and down again no problem. Looked a bit slow, but calculation for a 6cm pulley at 50rpm is 10m/min and it worked. The cable is 1.5mm dia polyester netting twine and climbs 1 foot in 10. The unit can manage that no problem, and the intended load (secret).

Here's prototype number 2 as she made the climb. New pulleys on order from technobots with grub screw fixings, pulleys are wider mouthed and have also ordered correct drive belt in neoprene. The current pulleys are just push

fit on 4mm shafts. Looks like I will be using 3mm clothes line for the cable, with something like a 10kg weight on one end to give a taunt line and take out any stretch.

Jobs a good 'un, as we like to say over here. Now to build prototype 3, the bits will be here tomorrow. I've even considered small geared drive unit with ESC for more speed, but am afraid the load might come crashing down if the drive skips the cable.

I'll let you know, aye, Kimmo

[Author]

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