1 reply to this topic

[rsawycky]

Hello,

 

I'm working on a new coaster for Christmas 2021 and its my biggest yet. I have a 12V DV motor I use with Knex for extra speed and torque. My issue is I have never had a chain lift this long before. I'm noticing a lot of tension to pull the chain even when no train on it. No gears are stuck and the chain has enough length where its not tight when resting. I think its the pure weight of the chain. Any tips for chains this long?

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[Steelwheels33]

Hello rsawycky,

 

First, welcome to the forum! Sorry for the late reply, there are not too many of us who still actively post and stay on top of these forums.  

 

That is certainly a big lift!  Excited to see how it pans out.

 

I have created a couple of pretty large lift hills in the past. One project, a custom intamin giga model back in 2011 that I started but never finished, had a 7.5 foot hill at the same angle as yours. I found I had the same issue. I was not using a custom motor, but I tried a drill and I also tried the electric knex motor pack (hard to find now) and the stardard motors. 

 

First off, be cautious with trying to gear the lift for speed. When you do so, you lose torque. There will be much torque required for that hill, especially if you plan on using weighted trains and a long coach (5+ cars). If you do decide to gear it for speed, the 12V motor you are using should be able to handle it. BTW, i'd like to see this motor if you could show a pic!!!

 

That said, that kind of torque, especially at a good RPM, could disengage the chain pieces or maybe deform them, but I think what would be more likely to happen is that the gear axles at the motor drive point or the top (drop) of the hiil would bend so much that they would become dislodged from the structure. Make sure you are beefing up your structure, escecially at those points of contact between the grears/chain.

 

The easy solution to this would be to use standard gearing and have a kind of slow lift. Slow and steady means less things breaking, lol. Make sure all the chain pieces are snapped together in the same direction, and they are snug. Sometimes the red gears are not the right tolerance in the middle hole, and this can cause friction between the gear and the knex rod axle. You can try to use graphite lube if it helps. The red gears should spin freely around a standard size rod, when they are not part of the drive system.

 

Another thing that you could consider is to not even use a chain. I invented a type of cable lift system with my 2011 design. I used small gauge metal craft wire that did not bend and stay bent. It had a catch car thing kind of like a launch would, and was run through pulleys created from the hub of a large KNex wheel with the rubber removed. It actually worked!! The hard part was making sure that the wire ran up the very center of the lift hill.

 

So because I could not use the center tube you would usually use with the chain (the cable would always fall over to one side) I had to invent a sort of carboard insert that fit between the two running track pieces and over the track connectors so it was a nice smooth valley all the way up the hill. Needless to say, that system had it's own challenges.

 

I hope some of this advice helps!!  Please let me know if something I said does not make sense or needs more explanation.  And...let us know how it goes!  You can post in the K'nex Coaster Construction forum the coaster build if you have any more progress - we would love to see it!

 

-Steelwheels.

 

-check out my final video for Tierra del Fuego!!