58 replies to this topic

[coasterguy]

Here is my new building tutorial for a cobra roll. the finished product is around 2 feet or so. i didnt really measure it though. anyway i will have pics posted here with a description in each post.

Things to Remember About This Inversion
-the cobra roll is one of the hardest inversions to put in a knex coaster since it has to reach the same height twice.

-this inversion is somewhat large and so the track needs a lot of support to keep from slowing the train down. all the supports on this inversion i built are needed (unless you dont mind the train losing a lot of speed) and so taking some of the supports of should be done at your own risk.

-you dont want the corkscrew-ing part of the cobra roll to be too tight as to slow the train down so be careful of that.

STEP 1: the base
this part is very straight forward. the only thing to be careful of is placing the 3-D connectors in the correct directions. the right side with the crossbraces will be the entrance/exit to the inversion. the green/red/orange rods inside each box are optional so if you are low on those pieces you can leave them out.

[coasterguy]

STEP 2: vertical towers
these 2 towers will be where the train makes its climb into the half loop before the half corkscrew. the green/red/orange rods in this structure are important so you need to have these in there. note that the 3rd crossbrace up the tower is connected by snapping a orange/black 2-way connector to a white rod that is snapped on the the yellow/grey 180 degree connector. this is there to create a smoother track for the train to ride.

[coasterguy]

STEP 3: between the previous towers
now this step can be skipped without causing too much of a problem. it doesnt take many pieces but if you need to you can skip it. the purpose is to sturdy the 2 towers you just made. it creates a triangular prism.

[coasterguy]

STEP 4: corkscrew support towers
the purpose of these towers is to support the half corkscrews. the will be built directly above the entrance/exit to the inversion. the only kinda tricky part to this step is the crossbrace that comes of the grey rod near the top of the tower. using the little black pieces that were used to connect the fexi rods to the lift and other various places in the screamin' serpent, i supported the crossbraces about 1.5 inches up the grey rod.

[coasterguy]

STEP 5: between the corkscrew towers
these supports are used to hold up the track between the 2 half corkscrews. you can add more supports coming off these supports at a 45 degree angle towards you to keep it more sturdy, but you dont really need to.

[coasterguy]

Overview of supports so far
this isnt a step. i have here a pic showing what you should have so far. there are the 2 half loop towers with the section in between in the background and, in front, the corskcrew towers with the section in between there.

[coasterguy]

STEP 6: top supports
these will be the last supports. note that the pic shows just one side built. this is so you can get a better view of it. to see both sides built look at the next pic. they run on top of the other towers you have built. there are 2 spots on each of the top support sections that will have the flexi rods go through the little holes in the grey connectors.

NOTE: after reviewing this step i realize that the 2nd grey connector that you run a flexi rod through is hidden. for a better view look at the next pic.

[coasterguy]

Congrats! you're done with the supports
now you should be done with the supports structure. the attached picwill show you what it should look like. only a couple steps left!

[coasterguy]

STEP 7: flexi rods
this step can be annoying. what you have to do is put all the flexi rods in for the track. you may find yourself in a spot where the felxi rods won't fit right. if this happens you can either start over or stick a flexi rod of a different size to make it fit. if you dont have different sized flexi rods (i got mine from the ferris wheel set) you can use hard rods, but that may prevent you from having a smooth track.

[coasterguy]

FINAL STEP!
in this step just put in more crossbraces in the spaces in the track and stick on the tubing. try not to have to splice the track during this inversion as that can slow the train up even more.the pic attached should be like what you have.

final note: the straight sections at the entrance and exit of the inversion aren't needed, i simply made it straight to fill the space.

[coasterman1221]

Great tutorial coasterguy27! i might try it

sometime

[jmrtc89]

Can we have a head on pic please? And is there a

certain manufacturer your going for on this?

Anyways, Great

tutorial!

[coasterguy]

i cant get more pics since i took it down, but you should

be able to build it fine with the pics i posted. also i wasnt going for any specific

manufacturer, but i do go for the b&m smoothness so i guess b&m.

[jmrtc89]

I was just curious if it had the same front shape as

B&M. That kind of shaping may be more speed effective.

[knex_krazy]

I'm actually using this cobra roll on my new roller

coaster in construction(you can find its topic in construction under 'down is goin

'or something)
but the cobra roll here looks very smooth but im gonna find

out very soon if my train will make it round with my drop(drop is a bit more higher

than the supports of this cobra roll).
Knex_Krazy.

[coasterfreak11]

Great cobra roll! Makes me want to start

building again...but eh, I'm out of supports, can ya believe that??

[Westside7th]

The tutorial looks good. I wish you had an estimated

drop height before this inversion so we know how tall the drop before this element

should be to make it through. Hopefully I can include a cobra roll in one of my

coasters.

[coasterguy]

that may have been a good idea to build a drop. i did

push the train through a few times and i think to be safe the drop into the cobra roll

should be around 3 or so feet. glad you all like it btw

[knex_krazy]

Ok, just built and tested the cobra roll on my new

model (whiplash in construction part of forums somewhere with no replies)the cobra

roll is excellent very smooth had no problems but it didnt make it as there was no more

speed i used wd-40 but still nothing so im goin to make the drop 4 grey rods high

instead of 3 so it eill make it.
Knex_Krazy.

[coasterguy]

glad it worked out for the most part. cobra rolls in

general are really hard to put in a knex coaster. im sure raising the lift a bit will work

fine.