The SCTA rulebook calls for a 1/4" thick steel plate - or thick individual lugnut washers - to reinforce 'Mag' wheels. The plate would be 6" - 7" depending since that's about the diameter of the Mag wheel surface step where the lugnuts go. Both the plate and thick washers are retained by the lugnuts. I'm not arguing the point, but I wonder how much additional strength a 1/4" x 6" steel plate would give during side loading? Also wondering if the underside of the plate should be flat all the way across or would it be better to cut a step, say .020 - .040 deep from the middle hole out and stop 1/8" - 1/4" from the edge. In other words, get the loading out away from the middle all you could or does it just not make any difference? As a small fwiw, I've seen strength figures for five lug wheels and how they are compromised by leaving one lugnut off. The loss of one lugnut brings wheel strength down to about 57% of the same wheel with all five lugnuts installed. Something to think about when you see some of the WonderWagons driving around with 4 lugnuts on a 5 lugnut wheel. And . . . God forbid, I saw a late F-250 with big wheels and tires with only 4 lugnuts on the front and 3 on the rear. He nailed it at the stoplight and I let him go. Figured there'd be a big cloud of dust further up the road....
If I'm reading this right, you're basically asking for a comparison between a solid steel sandwich plate vs. an individual thick washer for each lug point, correct? Is this is the case, it would in theory, help to distibute the load better than individual washers. As to an actual percentage, or some ball park numbers, we would need to know a little bit more about the conditions here, but I'm sure someone would be silling to run some theoretical numbers. That probably didn't help you, but I said it anyway bececause my fingers felt like typing something and you always try to help me with my problems, soooo... okay... I'll be quiet now.
It would be a hard question to quantify since there are so many different configurations, one would be the shape of wheels. A flat plate might add a lot of strength to a Centerline wheel, but on a Torque Thrust type it might induce a stress point out further on the spokes and not help, possible hurt since you are loading the wheel away from where it is designed to carry said load.
It might be a little stronger to use the 1/4" plate, but I wonder if it kind of defeats the purpose to run lightweight mag wheels, if you wind up installing some big steel plates. 1/4" thick steel weighs about 10 pounds per square foot, so a 6" disk of 1/4" steel would weigh about 2 pounds. I guess if you go with the plate, you could cut a big hole in the middle of it to lighten it up.
Scooter, what I'm asking is bare wheel vs wheel with plate. I threw in the thick washer bit since the rulebook mentions them. They're probably talking about CenterLine's 3/16" thick lug washers which strikes me as a really good idea on any Mag wheel. (Mag wheel defined as aluminum wheels we're all familiar with nowadays.)
Quote:Also wondering if the underside of the plate should be flat all the way across or would it be better to cut a step, say .020 - .040 deep from the middle hole out and stop 1/8" - 1/4" from the edge. I would think any kind of machined step or sharp thickness variation would be a stress riser, a good place for a tear or crack to start especially under a transverse or side load
aluminum is soft. steel is not. the plate is to keep the lug nuts from pulling through an aluminum wheel. generally, failure of the wheel outside of the lug hole area is not a concern.
btw i don't know where you're getting the "mag" wheels part from. it's mandatory for all non-ferrous wheels where the lug nuts directly contact the wheel surface.
I was just going to add that. I have some old factory aluminum wheels with the taper seat that have gotten wallowed out of round.
2002 SCTA rulebook, Pg. 16. Rule 2.G Wheels: The use of genuine magnesium wheels is discouraged, but with the proper test certificates they can be used. I'm guessing that the problem with non-ferrous wheels isn't the lugnuts pulling through the 'soft' aluminum, but rather breakage in the hub area of the wheel if the car gets sideways and the wheel digs in . . . which seems to spell doom whether the wheel breaks or not....
well your guessing is totally 100% WRONG. do you normally not listen to people when the give you the answer to a question? i think i'm qualified to give you the correct response considering that i've been an scta tech inspector for over ten years and i also happen to be the son of the guy who wrote a majority of the rules as they currently stand and that guy has been around the scta since 1967. don't listen to me, i don't know anything about scta rules.
The fact that washers are one alternative method should tell you that they are not concerned with breakage, but rather pull through.
and to further my point about the lug nuts, would the scta give you the option to run big fat washers under the lug nuts if their concern was the hub area breaking? the point of the rule is to prevent steel lug nuts from pulling through something like a spun aluminum wheel. five washers obviously aren't going to strenghten a wheel enough to prevent the hub area from ripping out. cast mag wheels are discouraged because they're typically brittle and once damaged (cracked) are prone to fail. the rules also state to use wheels that are specifically meant for competition use. these types of wheels are usually constructed in such a way as to decrease the likelihood of the hub area ripping out of the wheel.
Typically when gathering opinions in a discussion such as in this forum, it would be prudent to voice your thoughts and discuss them with other people. If a person has some genuine insight to add from an "expert" source, it would be taken with much greater weight if they site their sources, or in this case, qualifications. Information of unknown origin is worthless.
it's a straight forward common sense rule like the rest of the scta rules. hotroddon was able to figure it out. do i really need to disclose myself as an "expert" when the answer was pretty obvious? C9 had obviously already come to his own conclusion and dismissed my answer because it wasn't what he wanted to hear. why? is my post count not high enough? why is his guess any more qualified than my not-guess? do a quick search for posts by me and you'll find that i've participated in many threads concerning scta rules and disclosed numerous times that i'm an scta tech inspector and have offered my assistance to anyone with questions. or you can probably look at my sig and infer that i at least run at the lakes. either way, he's got his answer now. no engineers or metallurgists required.
I appreciate the answers as well as the expertise behind them. I note too that the rulebook doesn't explain why one or the other is allowed or which one they would prefer you use. I note too that your field of expertise is not noted so I hope you'll forgive me for that. Since I asked the question it's obvious I have no experience in this particular area and I am willing to listen. Seemed that if SCTA mandated them, they'd be a good thing to use on the street. Here's what I'm looking at doing. I have a pair of nice, narrow mags with two bolt patterns drilled in them to use on the front of a roadster - perhaps 1200# or so on the front end. I've seen dragsters with ten bolt holes in dual pattern mag wheels. Generally, not too much side loading in a dragster and the multi-drilled holes handled the HP (HorsePower) loads of the day. So thick washers wouldn't work for me, but I think a reinforcing plate would add a good degree of safety therefore the question as stated. Slot mags fwiw, so the plate lays flat on the hub area.
Keep in mind that the 'plate' will have to be in full contact with that portion of the wheel. NO room for any voids, especially at the lug nut clamping area. .
my mistake for not clarifying in advance. it's one of those rules that requires a little bit of interpreting. a plate or ring wouldn't really work on something like an old school american mag wheel where the "spoke" would interfer. in this case the washer is used. on a flat spun aluminum wheel the ring is a better choice. eh i don't know about that. the point behind the rule is wheel retention in the event of the wheel seeing massive latitudinal load during a spin. that not spins can't happen on the street but a retaining plate is probably a bit overkill for a street car. ah, the reason for the question is revealed. as mentioned above, the idea behind the scta rule mandating plates, large od washers, and 1" lug nuts is to retain the wheel in the event of a spin. the concern is the lug nuts pulling through the wheel, not necessarily to strengthen the hub area itself. i guess my thoughts are that you shouldn't really be doing spins at 200 mph on the street so the chance of the lug nuts pulling through are very slim. the chance of a cast mag wheel breaking are definitely there if you smack a curb or get into an accident but you're getting into an accident regardless and there will most likely be collateral damage. in other words, i don't really think a retaining plate as described by the scta rules would benefit you much on the street in regards to safety.
C9, you a man full of tact and grace. Beef Stew, you may be an SCTA god and all but geez, lighten up!
I happen to be the son of a guy who was a postmaster for nearly 40 years, and wrote a lot of the processes pertaining to RFD in some of the midwestern states. That doesn't mean I know anything about how the organization functions. All I know is that stamps have gone up since he retired........ The point is, I give you credit for what you know about SCTA based on your experience as an inspector, but being the son of a rules writer doesn't mean a lot when it comes to knowledge of the rules. Like Don Martin once wrote in Mad Magazine "Some sons of brilliant fathers are such disappointments, that it would seem enlightening doesn't strike in the same place twice".
You got that wrong fella. Beef stew is right to take the stance he did instead of joining the usual Chattering cheer squad that huants the HAMB. C9 was literally calling into question the rules concerning mag wheels .If C9 took time to read the first part of the rule where it says the use of mag wheels ( meaning any type of alloy wheel ) on the salt is discouraged, he would 'possibly' come to understand that 200mph is the wrong speed to suddenly discover what many who went before him already knew,that old school mag wheels are known to fail in a spin or slide at those speeds. The rules may be cumbersome and take some time to understand but they were written by those who had been there and saw what happens when things go wrong. if a driver doesn't want to abide by the rules then they don't run. Simple.
wasn't implying that simply because my old man wrote the rules means i automatically know them. i was however implying that i am uniquely qualified to provide answers as to WHY the scta rules are what they are because i can go straight to the source and say 'hey dad, what is the reasoning behind this rule?' and i get an answer straight from the guy who wrote the rule. make sense?
man oh man you sound just like me. unfortunately many of the scta rules (and other sactioning bodies) are reactive. they're a response to an incident or event where someone was hurt or killed and are in place to prevent such an occurence from happening in the future. now some rules are pro-active but most stem from real world incidents that actually happened. there is a story behind every scta rule. but is it necessary that every single rule has a disclosed reason behind it? no. you didn't question your old man when he told you to do something. you did as you were told. think of the scta as your dad; do as your told and your chances of having fun are significantly increased. don't like our rules? that's fine. we don't have to let you run.
Right or wrong I just said lighten up. There are more tactful ways than jumping up and down and telling someone how wrong they are. And heaven forbid we question any of the rules! Sounds to me like you're one of the lemmings. It's fun to ponder out of the box once in a while. Yes most of the rules come from hard learned leasons but occasionally Technology and/or a different line of reasoning can offer possibilities that were once unthinkable. Isn't that what hot rodding is about? I'm building an early 60's Dragmaster style digger. To meet all of the NHRA rules means I have build it like a full blown current TA/D car. I'm building it to be safe but I am NOT going to be put into a box and limited by the rules of today when I'm only going half as fast.
O man thats funny ,half speed so half assed. Im in tears you should use that in your avatar. I probably will apoligize when i stop laughing .
you sound like quite the romantic with your thinking outside the box and questioning the rules and all. but we aren't pondering the rules of life here man. this isn't philosophy. we're talking about a sanctioning body that establishes the safety rules for a certain type of racing. if you don't build your car to meet NHRA specs i can confidently say you won't be running at many (if any) NHRA tracks. same thing goes for the SCTA. what different line of reasoning is there? you follow the rules or you don't race. it's that simple. end of story.
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