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Chain and CVT guarding

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jtrnw View Drop Down
Double Secret Probation
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jtrnw Quote  Post ReplyReply Direct Link To This Post Topic: Chain and CVT guarding
    Posted: Mar/17/2017 at 9:49pm
I've been a lurker on the forum for a while, and I finally decided to jump in. This is my first year on Baja (and sadly my last, senoir)

Regardless I've finally stumped the search function. I'm working on the guarding of the CVT and chains on my team's car, and I'm looking for ideas.  Rule B15.2 says

"Rotating parts must also be guarded all around, in addition to the guard around the periphery. All around guarding (finger guards) must prevent small, searching fingers from getting caught in any rotating part. Non rigid, fabric coverings such as "Frogskin", Ceconite, and neoprene are unacceptable for use as finger guards. A complete cover around the engine and drivetrain is an acceptable shield."

My teams driveline package is very tight, what I'm wondering is if I can use the engine as "part" of my guard. If there is nowhere for a chain to escape if it cuts loose would that be accepted? Or does the guard have to guard the engine as well? I can always create a box for the entire driveline, it'll just be huge and heavy, and there must be a better solution. Maybe there is another solution I haven't thought of. I've included a cad picture of the driveline layout and one area of concern below. What do you guys think?

http://i.imgur.com/w5bVqKrl.png

The Orange circles are large sprockets. What I'm concerned about is between the last sprocket and the second to last. As can be seen below the small sprocket wound up a little closer to the muffler than intended.

http://i.imgur.com/2XbNMoBl.jpg
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SIyer View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SIyer Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 8:57pm
I think that's a question for the SAE tech inspectors. My 2 cents is that it will not suffice for a couple reasons:

1: There's enough room to get a finger in there (you'd have to be stupid, but it can be done)
* Take note of the term "searching" A team member is fiddling with the engine while it's running and suddenly you exceed CVT idle speed, is their potential for their fingers to get caught in a chain (or breaking chain?)
2: Do you really want your chain flying into your exhaust?
3: You need to cover that spinning shaft as well which looks more exposed anyways

That said, if I recall correctly, they allow you to mount things to your exhaust cage (so long as you dont modify the cage itself and it's rigid) so that might be worth investigating for weight.

As a side note, have you left any room for adjusting chain tension? Your bearing block mounting looks really neat and clean, and the rear end looks very compact, nice work!
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jtrnw View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jtrnw Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 9:49pm
Thank you for your reply! I thought about asking a rules question, but I didn't know how to word it concisely, and I figured a discussion might be more useful anyways. 

1. The searching finger thing seemed kinda strange to me since the only opportunity for it is when the car is parked, but I see what you mean.

2. The thought did cross my mind, but the exhaust seemed pretty tough, and based on the torques we should see I don't think we're at too much risk of a chain breaking. But then again I don't have a lot of experience with chains. 

3. For some reason covering the shafts never occurred to me. That could have very easily been one of those duh moments down the road. Thank you!

We have two pit bike spring type chain tensioners, one per chain that should mount up on the bottom of those chains. Whether or not they work well enough is still to be determined.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Mar/21/2017 at 7:16am
as said above, make sure that shaft is covered. we got busted for that about 6 years ago and had to rig something up at comp out of sheet metal. much easier to do in a nice warm shop. 

One of the main reasons behind the "wandering finger" rule is for the recovery crew. most often, the recovery team at comp is comprised of local volunteers from the host school who have never even really heard of baja, let alone, know the risk areas. when you have 2 cars stuck together and 2 drivers yelling at you to get them back on the track (drivers are rude in the heat of racing) you just grab whatever you can to pull on to get them going again. often, the drivers are also trying to get themselves unstuck at the same time by flooring the throttle. last thing you want is someone to slip and their finger to go into a speeding chain.  This mindless grabbing is also the reason for the sharp edges rule. 

as for weight, remember that the 1/16" steel or 1/8" aluminum is only required around the periphery of the chain/sprocket. everything else can be lightweight plastic / gfrp / carbon.  
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