29 replies to this topic

[RCT2123]

You know how SS wheels aren't directly on the track because if they were they the train couldn't go anywhere? Well clearly real coasters aren't like that, so what mechanisms do they use to achieve things such as tight turns and elements? I seriously have no idea, and I have wondered forever...

Please I only want answers that are very explicit or ones with pictures. If you don't know or want to know the same question don't post. I just want answers. Thank you...

-Rct2123:cool:

[Coaster55]

Most coasters will leave some space between the wheels and the track. I've seen Titan at SFoT's bottom wheels not spinning when it pulls into the station, and I've also heard Arrow/Vekoma trains have a lot of space. I'm not sure if there is small between the side wheels, though.

Here's a few pictures I have of Intamin trains off the track,





And my favorite,

[RCT2123]

Most of the wheels pivot though do they not? I was looking at Maurer Sohne's Skyloop, and there wheel base is basically this...



The black being the wheels and a rod connecting the wheels to a main base. The circles represent the direction this joint allows them to turn. The red represents the direction...

I understand one and two, but why doesn't the train sag down in the third situation? All the weight is on the middle where the main rod is connected too, and even though the length doesn't change you thing there would be some sag...

Help?...

-Rct2123:cool:

[CP-ephY]

Who says if the SS wheels were directly on the track it wouldn't go anywhere?

I'm not really sure I understand your drawing, but I can tell you with certainty that the bogies on B&M trains are all rigid (i.e. fixed). The only movement is rotation of the whole wheel assembly about the same axis as the side friction wheels. There is a plate sitting directly above the wheel assembly as you can see which is mounted to the train. There could be a shaft going through the plate that allows for the rotation. That's about it. But do explain your drawing more clearly as I'd like to know what you're trying to say.

[Jogumpie]

B&M has springs on their wheels to tighten them to the track.

[coastergeekrtc]

Do you remember Tyrant's SSC Car Redesign? That gives a good idea of how the wheel assemblies work.



Like ephy said, the entire assembly rotates along the Y- or vertical- axis. This is the axis parallel to the side wheel axle. It also pivots along the axis parallel to the road wheel axle. This allow the assembly to pivot and adjust as the train traverses changes in height (i.e.: hills, top hat, lower lift, etc.) The two assemblies are tied together across the track with a tie bar so that they always face the same angle and hug the track. You can sort of see what I mean in this picture of the custom model that started CoasterDynamix. Each wheel sits in a pivoting assembly with either a spring or rubber material that puts tension between the track and wheel, causing the train to hug the track.

[TripleHelix]

Here's a good Intamin train pic.



You can see where the assembly pivots (it rotates parallel to the ground) but it doesn't move up and down, which is why there is a gap in the wheels above the upstops. There's probably on of those rods in between to keep them the same direction but it's hard to tell.



I don't think this Skyloop train pivots on three axes... I only see one?

[Jesperdude]

I don't think this Skyloop train pivots on three axes... I only see one?

Me neither in this pic:



But is this of any relevance?

[~stεεlspectrum~]

It seems to me that Knex trains wouldn't lose speed as quickly if their wheels were pressed against the track, using either springs or having them pivot, like ^ pointed out.

If anyone has ever tried making 4d trains (or any large, custom trains), they know that the train looses speed really fast. I tried it, and my train shook and rattled side-to-side so much that it only regained about 1/4 of the height on the second hill. Is it possible to fix this?

[Jesperdude]

I tried it, and my train shook and rattled side-to-side so much that it only regained about 1/4 of the height on the second hill. Is it possible to fix this?

Maybe you have to add more cars to the train. But I don't know how many trains you were talking about and how many trains you have.

[coastergeekrtc]

I think there are many factors to why the Knex trains are not as efficient as real coasters. The biggest being you can't scale gravity.

It really helps that everyone builds rigid supports so that the track doesn't budge from the train traversing it's course, but no one can help that the rails / tubing is soft. If you were able to layout a Knex coaster on the computer so that you could bend metal rails into the shapes you need, I think that would help a lot. Or if someone found a much harder plastic to use for the rails, much like the CoasterDynamix rails.

Also, the trains are horribly inefficient. The wheels are not kept in place so they are allowed to move along a axle, rubbing against the wheel assembly. Precision is a must with such a small scale and we know that the wheels leave gaps between themselves and the track. The tolerance definitely could be tighter. Most of all, I think bearings would prove to be more efficient wheels. Problem is that at that size they sure are expensive.

[RCT2123]

Thank you, this all helped very much...

I was talking about in this vid. You can clearly see 3 pivoting points. Check out 1:55 in this video...

http://www.youtube.c...h?v=ZjH3IGnygO8

The reason I ask is my school recently got a printer that makes 3D objects with plastic. Since I am close with my teacher I know he will let me design whatever I want and make it. So I figured why not design better SS wheels? So that is my new project. I knew that by making the wheels closer to the track I would need to make the wheels pivot in some way. Now here is this thread...

So no promises or anything, but I will be working on that...

Please opinions are welcome on what I should do. I want to make it so all I have to do is screw it to the current car without making new holes. So tell me what you think...

-Rct2123:cool:

[TripleHelix]

I want to make it so all I have to do is screw it to the current car without making new holes. So tell me what you think...

-Rct2123:cool:

Does your school have a 3D scanner? That would really come in handy there.

But I see what you're saying about the three way pivoting wheels. I don't know how they could pull that off either...

[coastergeekrtc]

^He just needs a pair of calipers. The SS trains are not too complex to measure by hand. A 3D scanner would be pointless, IMO.

The reason I ask is my school recently got a printer that makes 3D objects with plastic. Since I am close with my teacher I know he will let me design whatever I want and make it.

Hey rct2123, watch out for how close you get to that teacher. You don't want to end up like IMC!

[RCT2123]

I didn't mean that close. I only get close enough until I get what I want CAD wise not sexual wise...

-Rct2123:cool:

[CP-ephY]

It looks like a joint that lets it move up and down and left and right.

[~stεεlspectrum~]

You could have the upstop wheel pivot vertically, and attach that pivot axle to a spring. That would keep both the running wheels and upstop wheels as close to the track as possible.
Now you could have the whole wheel assebly be able to pivot side-to-side to compensate for tight turns in the track.

Would that work?

[coastergeekrtc]

Lots of things could work, the problem is building them and having them work at such small scales. It may look good on paper but reality is entirely different.

[~stεεlspectrum~]

Lots of things could work, the problem is building them and having them work at such small scales. It may look good on paper but reality is entirely different.

Well, I guess it helps to have it as basic as possible then...
Two axles sounds simple enough...

[poizone]

I believe that Tyrant got it right with his redesign. We would just have to make connection points on the SS cars. And Tyrant's design wasn't overly complicated. I myself would buy the parts for about 20 sets, and put them together myself. Then do the connection testing on my own.

I do believe that he had CAD drawings of his wheel assemblies. And by the way, B&M and Intamin use springs to keep the wheels against the track.