NL2 Riverview Bobs (from blueprints)

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NL2 Riverview Bobs (from blueprints)

Post by Sora » Sat Jan 07, 2017 7:16 am

Here is my recreation of the famous Riverview Bobs. After seeing various claims on the net that the ride would be unsafe to build today because the g-forces were too high, and seeing wildly differing figures on how high the lift was, I decided to go back to the blueprints in the back of Derek Gee and Ralph Lopez' book "Laugh Your Troubles Away" and attempt a definitive version from them instead of judging all the heights from photographs.

In their book, Gee and Lopez say there are various prints for the Bobs still in existence, some of which have lift heights of 77 feet. Derek told me in an email that from research they have done since the book's publication, the final built height has been determined at 64' 9". The blueprints in the back of "Laugh your troubles away" have a written lift crest value of 54' 9". My thanks to Randy Rasmussen, a civil engineer who worked on the restoration of the Belmont Giant Dipper and a lifelong Fred Church devotee, for pointing out that an error halfway up the hill changes the gradient from Church's standard 4:10 to 3:10 resulting in the lift being 10 foot shorter at the top than it should be. I wrote to Derek, and he confirmed that the highest bent was also standing on a 10 foot mount, so the 54' 9" figure is the height of the bent, not the height above grade. There is also a mark in the profile diagram on the previous page which looks like a 5 turned into a 6, so 64' 9" was determined as the final height of the lift.

I have kept as close as possible to Church's markings. All radius values are correct, all node (bent) spacings are correct bar a couple of exceptions, all the banking angles are as marked, and suspicious height values in the horizontal plan were cross-checked with the profile diagram. Where there were errors in both, I used Excel's line graph function to get as close as I could to the profile curve Church drew in the blueprint. Thanks again to Randy for his valuable assistance on Church's track construction and help in working out the scale of the plans in the book.

There is a collision between the horseshoe of turnaround 1 and the inner fan curve of turnaround 3. This is due to a) a node at the end of the fan turn which the computer wouldn't let me place correctly no matter how hard I tried, and b) the width of Church's tracks, including catwalks and railings, being narrower than NL2's. This width variation also explains a couple of other places where adjacent runs' catwalks overlap, and yes I know the ride is under-supported. I simply do not have the time or energy to build over 300 bents and supports from scratch. Others are welcome to have a go, though, I'd love to see it. :)

There is a tunnel marked on the blueprint, running from just outside the station to the curve onto the lift. This isn't shown in any photo I've ever seen, but I've put it in anyway for historical interest. You can always turn it off.

The extent of the mid-course brake runs are as marked on the blueprint. The one on the high front turnaround did extend partly around the start of the corner, but there is sadly no setting for skid brakes, so it looks a bit weird with pinch brakes on a curve. The mid-courses themselves do not affect the train unless a block ahead isn’t clear. However, when they release, the trains won’t make it back to the station. I decided that in practice a bunch of strong attendants would have given the train a good push instead, but adding friction wheels to simulate that seemed like an unacceptable option.

I toyed a lot with the station and final brake run. In the original, it was a double station with a transfer track. The NL2 train is too long for a correctly dimensioned transfer, and if I use a second station, the building is built right through the roll out tunnel. In the end I settled on a brake run taking up the space of the transfer and offload platform. Friction wheels were used on the two brake runs for two reasons: first, in three train mode when the brakes release gravity doesn’t give the train in the unload brakes enough momentum to get into the station. The second is that by fiddling with the speed of the wheels I can effect a smooth stop similar to how it would be if the wheels weren’t there. Even with one train on the circuit, the friction wheels slow down the train.

Colours for trains 1 and 2 were taken from actual photographs. Derek said that train 3 was yellow with forest green accents. NL2 doesn't do accents, so I've got the forest green as the seat colour.

Finally, yes I know the ride wriggles from side to side during the turns. I don’t know why this is. In Excel the path is a smooth curve, the banking is also fine. I think NL2 just hates mathematically perfect circles. Anyway, I hope you enjoy the coaster. For its short lift it packs one hell of a punch! :D

Here are some photos:




Riverview Bobs final
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