Columbus' Second Coaster!

Sunday, November 21, 2004 8:48 AM
Ok i know the title is miss leading but really columbus is going to get a second coaster. And I am building it! I am constructing a coaster in my backyard. And i have created a prototype to see if the wheel assembly and track will work properly. Here are some pictures

I will keep updating this topic. But do any of you have experience doing somethig like this. Any suggestions? Or things you learned.

I am currently having a tracking problem. The tube is slipping through the hole between the guide wheel and the road wheel. *** Edited 11/21/2004 1:50:33 PM UTC by The Elf***

Sunday, November 21, 2004 9:18 AM
why are you using the tube.. make it like a wood coaster track and use wood??
Sunday, November 21, 2004 11:04 AM
Ok you try Bending Wood! and making it a 7 layer track!
Sunday, November 21, 2004 11:10 AM
ok dont ask for suggestions then

Sunday, November 21, 2004 11:50 AM
Do your wheels have any curvature to be placed on a tube that small?
Sunday, November 21, 2004 12:15 PM

skipper747 said:
ok dont ask for suggestions then

I think he was looking for suggestions that were in the realm of possibility.

Sunday, November 21, 2004 2:01 PM
Okay, I actually have some experience building this sort of thing- raven-phile and I did one that didn't kill anyone at least a couple summers ago.

First, if you're planning to have anyone ride it, PVC pipe is so far from strong enough to be somewhere between comical and scary. Our track was five layers of 5/4th by 6 decking, Decking is easier to bend than 2x8. Its also weaker, out length between supports was four feet. If you went to two feet between verticals, and only have one passenger, you could probably get away with five layers of pressure treated 1x6, which would be easier to bend yet.

If this is an indoor guy that never rises more than a foot or two off the ground, then maybe you'll just be hurt when it fails. If its an outdoor project thats supposed to be going up five or ten feet, realize you're taking your life into your hands. Do you trust your engineering skills enough to be confident when if you're wrong, you die? A test run with a sandbag won't prove that it won't catastrophically fail the next time around.

Okay, next, where are your upstops? Have you already designed your entire course and calculated that you don't need any? What about if the train stops midcourse on a bank?

I don't know the layout, but the casters you're using don't look sufficient to me. If they're rated 50 pounds each, and your designed car weight is 200 pounds including passenger, that is not sufficient. What happens when you start pulling any amount of Gs at the bottom of a hill? Where's your factor of safety?

One thing you are doing right is making your car's wheelbase one and a half times your track support spacing. This will minimize bending moment on the track. Not enough to save your bacon with that PVC track, but with sufficient track strength its a good design idea.

Here's the most important part. For designs where someone's life could be at stake, and the design itself is unproven, I suggest a factor of safety of at least six. What that means is that you need to build the thing to take a load six times stronger than your rated load. If the rated load of your car is 150 pounds, that means you need to load your test rig up with 900 pounds. Commercial coasters are likely designed with a FOS of more like three or four, but their designers know exactly what they're doing, what to look for, what the failure modes will be. You don't.

Please don't use the PVC pipe. Its reallly not sufficient. Decking like we used costs about a dollar per linear foot, so our track (just the track) was $10 per linear foot. With verticals and the like we were closer to $15 per linear foot. If you're only carrying one passenger, and are using a 2' support spacing, you can get away with less strong track. Here's what I suggest. With two foot spacing, get sheets of 3 ply 1/2 inch thick plywood. Cut this into 2 strips three and a half inches wide, four strips 2.5 inches wide and one strip 1" wide per 8 feet of rail. (the long way, you'll end up with 8' strips) These will bend nicely. Make your track out of these in the following manner. Build your supports. Next, run one layer of 2.5" strip around your entire track for each rail. This will bend nicely, but will be a little bit ugly in that it'll have discontinuous slope at the joints. Ignore that for now. Start and end the strips at the center of your horizontal supports, you may have to trim some. Next, start one support away from your current joints and run a second layer of 2.5" wide material around your entire track. This will make the second layer's joints all 2' away from the first. The third and fourth layers go on in the same manner. This will make your joints distributed evenly, which is important. When you have the fourth layer of 2.5" thick material done, get a C clamp and some 2" long ring shank nails. Now, clamp the rail together with the C clamp six inches from a support, and nail the four laminations together. move the clamp six inches and repeat. Put one nail ever six inches in the center of these four laminations, all around your track. This will pull the track into a nice flowing curve, and should stiffen it considerably. At this point, you can safely walk along the track. You're not nearly done, though. Now you move to your 3.5" stock. Depending on whether you want your upstops on the inside or the outside, align the 3.5" strip with one edge or the other. This will give you an inch lip under which you can set your upstop. For this row, also nail ever six inches, but start 4 inches from a joint, so that the nail is two inches away from the pervious one. you won't need the clamps here, just press the layer down and nail it ever six inches. Continue with a second layer of 3.5" track, and viola, track that won't kill you. Now, take a 1/4th inch lag screw thats 6" long. Predrill and countersink for the lag screw at each track to support joint, and then sink the lag screw (don't forget a washer.) You'll need to countersink it enough to have the wheels ride over it smoothly, and place it roughly centered. Now, take that 1" strip and run it right inder where your wheels will be. Secure this with 2.5" finishing nails so you aren't continually running over nailheads and lag screw holes.

Thats it, track that won't kill you. Now for the caveats: this design is good for loads up to +2g/0g vertically. It is not for designs that must ride on their upstops, the upstops should be used for emergency only. the bending radius of your design must be sufficiently large to not seriously compromise the structural integrety of the track laminations. I'd say keep it to a 4' radius of curvature at an absolute minimum for the top of hills and 8' radius of curvature for the bottom if hills. Keep lateral Gs below 1. If this is to be used outdoors, apply some sort of finish to the track so that it is not affected by the weather. I am a mechanical engineer, but do not have a PE license nor do I endorse this track as definitive without seeing the layout. This track design is based on experience and quick, back-of the envelope calculations. Verify its suitability for your design independently. That said, it is much, much better than using PVC pipe.

Now for advice based on my experience. Keep the design conservative, it'll be easier to build. Don't bank anything more than about 20 degrees, more than that is hard to build. You're much more likely to suceed with a shuttle coaster that you have to push or winch back up to the top of the first hill than with a continuous circuit coaster with a lift hill. If you do build a shuttle, build a spike at the end thats at least as high as your first hill, do not rely on brakes. Curves in general take twice to three times as long as straight track to build. If you really want a lift hill, use double pitch chain, at least ANSI 50. Less than that will be really, really hard for your dog to catch (we used ansi 60 single pitch and never got the dog working reliably, jsut too small an area to hook with the tolerances you can hold with a woodie) Realize that even with the track above, which is as economical as I can come up with and still be relatively easy to build, this is going to cost five to seven dollars per foot to build: plan accordingly.

Design wise our car had roller bearing wheels and a fully articulated train with a pretty stiff tubular aluminum frame. We lost about 1 foot of energy per 30 feet of track traveled. With simple sliding casters on a boxcar train I'd guess more like 1 foot of energy per 15 feet traveled. So if you want a 75 foot long shuttle coaster, you need a five foot tall life hill. Six or seven would be more conservative. All told including car you can probably build an 8 foot high, 80 foot long shuttle without brakes or a mechanical lift for about $1000.

Don't scrimp on your car, your life is riding on it, literally. For wheels I had very good sucess with 6" phenolic wheels with built in roller bearings for the road wheels and 2.5" phenolics with roller bearings for the guide wheels. They had decent bearings, great load ratings and cost about $7 each for the larger ones, $4 each for the smaller. For upstops I used grade 8 bolts with a stack of washers as a wear surface/roller. This was to facilitate pulling the car off the track without a transfer track. The car's frame was 2.5" square 6061 aluminum tubing with a 1/8th inch wall, bolted together with 1/4th inch 6061 plate. All told my car weighed about 500 pounds, but it was a four seater.

If your layout is reasonably tame (no negative Gs, no major laterals) and the box of your car is strong, a restraint system like that of kennywood's jackrabbit is your best bet: a fixed metal bar and a seatbelt. You can pick up seatbelts at any auto parts store for under $20. Galvanized pipe and fittings from Home Depot or wherever will probablly suffice for a bar. DOM would be better, but harder to work with and much more expensive.

Anyway, if I haven't scared you off and you want opinions on specific questions, or want pics of Josh and my coaster, or whatever, drop me a line at john.bellinger (AT) (with an @ of course)

Unless you're persisting in your plan to use PVC pipe. In that case I can't help you.

Sunday, November 21, 2004 6:21 PM
You did not just type all that.

camotose: you get the award for longest post ever that is not a trip report.

The Elf, Good luck with your coaster, your idea sounds pretty cool. *** Edited 11/21/2004 11:21:53 PM UTC by Alizabeth***

Sunday, November 21, 2004 7:15 PM
My advice after watching like all these real video shows, make sure you have a paramedic crew there so if you come close to killing yourself. You will have trained professionals on the scene.
Monday, November 22, 2004 11:16 AM
and don't forget to video tape your maiden voyage. Those precious mometents can make $$$ as crash videos... :) just kidding...
best of luck!
Monday, November 22, 2004 11:30 AM
Hope thats not your final car design, theres not much clearance from the bottom of the wheel to the bottom of the car... if you have a significant slope or hill, your going to scrape the bottom of the car and get stuck.

PS: dont kill yourself

Monday, November 22, 2004 3:38 PM
As comatose said no way Jose!

PVC is neat stuff with many uses, but not for coaster track. Using the current design I would stop production right now! I know your young and ambitous but you are building an injury machine, not a coaster.

Monday, November 22, 2004 3:59 PM
I'm an engineer too and this looks like an accident waiting to happen, convex wheels on circular track with a gap between the wheels bigger than the diameter of the track itself! That, and the pipe is no where near strong enough, unless you have access to an industrial steel pipe bender, use wood.

That said, I just found this link to a PVC coaster in some guys back yard and there is a video of some kid riding along on it!!! Scary stuff!!

Monday, November 22, 2004 4:11 PM
That is 2" PVC. I would have more faith in that than the gauge Elf is using. Wow the coaster in Austin is a shuttle coaster! *** Edited 11/22/2004 9:15:09 PM UTC by Markieb***
Monday, November 22, 2004 6:51 PM
I have actually ridden a coaster that was built with PVC rails.

It's the Pipeline Express at Putt 'N Pond Action Park in Fostoria, OH. The ride was built by Bailey out of Whitby, ON, and Bailey had a booth at IAAPA this year, so he's still at it. The ride was constructed from a platform at the top of a waterslide tower. The track was constructed using steel support posts, a steel center spine, and steel track-ties, but the running rails were PVC pipe, I forget how large. The track ties were welded to the spine, and attached to the support columns. At the end of each track-tie was a saddle plate which was attached to the PVC rail with several rivets.

Bailey built several rides with PVC track, but I think most have either been torn down or converted to steel rails. The one in Fostoria is presently SBNO, but I am not aware of any failures related to the use of PVC rails. The car design has its faults, and I believe the rides have suffered some unpleasant incidents, but I don't think any of those incidents was a mechanical failure. Someone once told me that someone had tried to jump from the coaster car into the swimming hole, but I have not received any confirmation of that incident.

I have on-ride video of the Fostoria coaster, the only trouble is, it's on 8mm videotape, so I have no way to play it back....and now I'm not even sure which tape it is on.

--Dave Althoff, Jr.

Tuesday, November 23, 2004 12:57 PM
As usual, Dave is right. There's no technical reason that as a material PVC couldn't be used. If someone really put their mind to it, a structurally sound coaster could be made from styrofoam too. There are a few practical problems as I see them with suggesting that PVC be used in this situation. First, PVC tend to experience brittle failure, especially when cold. Now, brittle materials aren't necessarily a bad thing. The problem is they don't really signal their impending failure. If they're designed with a good safety margin by an experienced engineer, this isn't a problem. It doesn't lend itself well to the "well, its never broken before" type of safety verification non-engineered one-off structures usually get. Secondly, the material properties of PVC are highly temperature dependent in the range of ohio air temperatures. So just because it held up one day at 65 doesn't mean it won't fail on a cold october day at 20 or a 100 degree scorcher. This problem can be engineered around, of course, but it can easily lead to a false sense of safety.

The third, and biggest problem, though, is a construction one. Yes, two or three inch PVC pipe could probably be made to work. However, 3 inch PVC isn't exactly flexible, so one would have to heat bend it. To make a nice smooth bend in pipe you'd need a roll bender. You'd also need a nice, even pre-heater. This can be made, and probably would not be prohibitively expensive. The frame could be plywood and the mandrels could be turned from scrap wood, if someone has a wood lathe laying about. The heater would be a little bit trickier. If the heater is too little, then bending would be a very, very slow process. Too big and you'd get deformed rails. making and tweaking the bender would probably take about 2 weeks, and $100 or so. Getting a McDonals job at $6 an hour for those two weeks (20 hours a week either way) would net $240. Add the cost of making the bender and a PVC forming rig costs you $340. PVC rails of sufficient strength are likely to be two or three dollars per foot.

TheElf, are you in a big hurry with this? Big hurries get people injured. You're not likely to get to ride this comfortably til spring anyway (or even safely with PVC). Your absolute best bet is to get a job (or some other source of income) going until you have enough money to complete the project properly. The worst thing that you can do is run out of funds half-way through. Save up every penny you make until you have 1.5x the amount you think you'll need, then start.

Tuesday, November 23, 2004 1:04 PM
Dave - were all the Baily Auto Sleds originally built with PVC and then converted or did some debut with Steel rails?

My interest is piqued because I got a chance at a Baily Auto Sled this summer in Canada. I found it more unnerving than most big 'traditional' coasters and wondered why we don't see more of these - expecially at smaller FEC's.

Edit - still getting the hang of that spelling thing

*** Edited 11/23/2004 6:04:45 PM UTC by Lord Gonchar***

Wednesday, November 24, 2004 1:58 PM
Gonchar: I don't know, and when I walked past Bailey's booth he was busy with somebody...besides I didn't think to ask. :)

--Dave Althoff, Jr.

Wednesday, November 24, 2004 2:02 PM
Heh. I figured if anyone knew, it'd be you. :)

It was worth a try.

Wednesday, November 24, 2004 5:19 PM
i think this is really cool. I could never do this.

Hope it works. If it does, send me a message.



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