Chain Guards

[RussMcB]

9.3.39. SCATTERSHIELDS/CHAIN GUARDS
The installation of scattershields or explosion-proof bell housings shall be required on all cars (except Showroom Stock, Spec Miata, Touring and Improved Touring) where the failure of the clutch or flywheel could create a hazard to the driver. Chain drive cars shall be fitted with a protective case/shield to retain the chain in case of failure.
Minimum material specifications are:
.125 inch SAE 4130 alloy steel
.250 inch mild steel plate
.250 inch aluminum alloy
NHRA or SFI approved flexible shields.

After reading the above, I wonder if the material specifications have been in place for a while (back when the rule was for scattershields only). Do you think they meant that chain guards have to be that thick and strong? I can only remember seeing one car that had a chain guard that would fit those material specifications.

[Purple Frog]

I think it is a case of the rule being "improved upon" numerous times. I believe those material specifications are for bellhousings/scattershields that are located in areas where a clutch/flywheel failure could harm the driver. (not a mid-engine chassis problem).
Then after writing that rule, they inserted the bit about chainguards in the body of the original language. It would have been better if it had been added the chainguard stuff at the end (under the scattershield specs). My opinion...You just have to build a guard to keep the chain from hurting you, or flying out of the car into my face shield.

[RussMcB]

That's my opinion, too. Of course, my opinion is worth nothing. It's easy to imagine a tech person looking at most DSR or FB cars and thinking they don't satisfy the rules. I guess it's one of those cross your fingers things. I wonder if we should petition for a clarification or rewording?

[cparsons]

My opinion is of even less value than yours, but I suggest that clarification be done now if possible. Russ, do you want to win the ARRC only to have some sore looser point out that you are not in compliance with the rules?
And a side bar, I will know what I have to do also. That to-do list just won't go away.

[RussMcB]

Russ, do you want to win the ARRC only to have some sore looser point out that you are not in compliance with the rules?

I think my best chance to win the ARRC would be for me to be that sore loser and use this rule against all the guys who are going to be faster than me. :-)

Your suggestion is good. I'm just trying to get a feel for how likely it is going to be a problem. It very well may be a non-issue, since (I assume), plenty of DSR cars have been racing without tank-like chain guards.

[Dave Gomberg]

I think it is a case of the rule being "improved upon" numerous times. I believe those material specifications are for bellhousings/scattershields that are located in areas where a clutch/flywheel failure could harm the driver. (not a mid-engine chassis problem). Then after writing that rule, they inserted the bit about chainguards in the body of the original language. It would have been better if it had been added the chainguard stuff at the end (under the scattershield specs). My opinion...You just have to build a guard to keep the chain from hurting you, or flying out of the car into my face shield.

Sorry, PF, but you actually have it backwards. The current language dates from 2003. Before that, the same specs were in place, but only for chain guards. The bell housing/scattershields were previously there without a spec.

The chain guard on my DSR is .125 4130 and it isn't really all that heavy.

And, FWIW, when chains break, they tend to go forward and destroy the engine cases.

Dave

[HastyHorn]

If you take a look at what the typical DSR has you'll see that it doesn't add that much weight. I wonder if you guys are envisioning a "full coverage" type of guard. The floor pan acts as a cover for most of my chain and the engine adds another 30 % or so. Basically, the guard just has to block the windows of opportunity for escape. Doesn't have to extend down and cover the sides.

Hasty Horn

[Purple Frog]

Thanks Dave and Hasty for the clarification.

[RussMcB]

If you take a look at what the typical DSR has you'll see that it doesn't add that much weight. I wonder if you guys are envisioning a "full coverage" type of guard. The floor pan acts as a cover for most of my chain and the engine adds another 30 % or so. Basically, the guard just has to block the windows of opportunity for escape. Doesn't have to extend down and cover the sides.

Hasty, would it be accurate to reword your interpretation and say, wherever there isn't something "in the way" (meaning, there is only air in between the chain and outside of the car), you need to have a chain guard made of those minimal materials?

I'm not sure all tech inspectors would go along with that. For instance, your floor pan is surely thinner. But if you accept that it's enough, where do you draw the line? Is my fiberglass engine cover enough? Probably not. Your opinion is that your floor pan is sufficient, but I'm not sure that would stand up to the written rule.

I would agree that an engine itself is enough mass to retain the chain and therefore a chain guard isn't needed there, but, is that a valid interpretation?

Unfortunately, this seems to me as another case of the rule being hazy enough so everyone just kind of forms there own opinion about where the line is drawn. In other words, at what point would *most* tech inspectecter deem "good enough".

I know I'm splitting hairs and probably being more of a jerk than necessary. I just want to have no worries about my chain guard, while at the same time not wasting unnecessary time on it.

I wonder if people would be willing to post pictures of their chain gaurds here to help us be clear on what is or isn't legal? I'll takes pics of mine and post then tonight.

[HastyHorn]

Well, let me put it this way....my chain guard has passed very specific scrutiny and the chain punching a hole through my floor pan (balsa center, double thickness of fiber glass) wouldn't do anybody any harm (besides driving over it) once it made it through...my point is that the D Sport requirements are the same (I believe) and our "guards" are pretty minimal. They would prevent it from being thrown into your face (if you were in the car or following my car) and they have passed many tech inspections. In addition we (C Sporters and D Sporters) are the standard that the inspectors are using as a standard for chain guards. Besides if you guys suddenly come up with some terrific design the standards might be raised.

I have "thrown" a chain or two in the past and the system has worked just like one would hope, the chain was retained within the confines of the car (and/or destroyed the engine cases).

I'll take some pictures.

Hasty Horn

[RussMcB]

Thanks, Hasty.

To be clear, I don't have any doubts that your chain guard isn't up to your own standards (or mine), and that every time a tech inspector has seen it they didn't question it. However, I wonder if it completely satisfies the rule as it is currently written. If that's true, then maybe the rule needs to be rewritten or clarified.

I think my chain guards would pass any tech inspector's muster. I'm actually pretty proud of the job I did with them, but if a tech inspector or compeititor wanted to give me a hard time, I might lose the protest. I guess it just rubs me wrong to have a safe but but possibly not legal part.

I guess I need to be completely honest and admit that I did not read the rule before I designed my chain guards. I simply looked around my shop and used what I had. I actually thought I was over-building them.

So, bottom line - I really only have myself to blame myself for being in this predicament. But, if there is a problem with the rule, maybe it should be addressed.

[carnut169]

Having seen pictures of your guards I've got to believe you would be fine... are they not .125" thick? They appear to be steel, er um 4130.

I used .250 thick aluminum and did exactly what Hasty described- covering the area the chain could escape from. The rule does not specify how long or where it needs to be... guess thats up to you.
FWIW I've passed annual tech 2x w/o any additional chain guard and have heard the arguement that the front sprocket cover/ engine are the guard. I did not want to go down the protest road so I installed a 6" x 4" (ish) strip across the top of the rear sprocket.

[RussMcB]

I guess as long as mine are (or appear to be) .125" 4130, then I'm all set. :-).

[RussMcB]

It was hard to get clear pictures. If they are confusing, remember that I have two chains (and chain guards) with a jack shaft in the middle.

You might also be able to tell that my main goals for building good chain guards were to protect the engine and oil tank. I could give a flip about the dumb driver. The team would be in much better shape if he had to be replaced. :-).

[Wren]

that should more than meet the rules. I would think that the chain guard should only need to extend down to the centerline of the sprocket. That should prevent it from ever escaping dangerously.

Formula SAE has similar rules and they are often needed.

[cparsons]

It has been my experience that Hasty has it right, as far as breaking a chain. Afer it eats the engine cases by the countershaft sprocket, it either locks up the engine because it got stuck there, or pretty much just falls off and slides along the ground for awhile. I have never seen one go flying (thankfully). I suppose it could, Murphy's law, but not likely. The engine cases take all the heat out of it.

[RussMcB]

My first design for the chain guard was around the entire chain. Then someone pointed out that I might want to give the chain a way out so it doesn't get bunched up and do more damage. You can see in my first picture that the bottom run does not have a guard. I left that open to give the chain an "out" (towards my floor pan / diffuser).

I guess as long as there is enough stuff in the way so it will likely "retain the chain in case of failure", then it's okay. I assume by the way the rule is written they do not want it sliding along the ground.

I've decided that I will run what I have and assume no one is ever going to make an issue out of it. If they do, I'll deal with it.

[cparsons]

Not to keep harping on this, BUT, I talked to a friend of mine and he reminded me the time we were riding and his chain broke. It ate the cases on his Honda and locked the rear wheel by wrapping itself in a knot back there. The moral of the story is that the chain can break and end up anywhere it wants. BYW - we were riding Honda 750 K0's , the original Honda inline 4's, and they were pretty new at the time. We got the chain off and I towed him back, about 30 miles, with a rope. I DO NOT advise that anyone ever do that.

[Mike Devins]

This has passed anual tech as well