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No Title -> Tires/wheels/braking -> Spokes are breaking to much...
Post Info TOPIC: Spokes are breaking to much...
Nathan McCaw

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Spokes are breaking to much...
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It seems like after every race we have to replace at least three or so spokes... What can I do to limit as many broken spokes I can?

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electrathon


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We run 48 spoke wheels and use over sized spokes (12 gauge I believe).  It really cut down on the number of broken spokes that happen. 

Side cornering stress is usually what breaks them, you could try slowing down in the corners laughing.gif

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Nathan McCaw

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Hahaha, I could try but I don't know if that would do me any good... Does the weight of the car play a role in breaking spoke too?

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electrathon


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Yes, the weight does.  Steering geometry has a greater role.

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Nathan McCaw

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Really? How so?

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electrathon


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If the steering is properly designed (virtually none are) when you turn your tires will lean to the side like a cornering bike does. Bike wheels do not like side load, they like center loading, pushing down. When the wheel is upright and the car is turning, the stress is not in a manor that a spoke wheel is designed to take, then you break spokes.

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nathan McCaw

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Oh I see. Im making a new car this year so I don't know how well my car can corner yet... Since I had the batteries on the sides of my car last year, do you think that put a lot of stress on the wheels?

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bd64


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I think % foward weight is an extremely important factor in design.  Too much foward weight will brake motorcycle spokes, that along with poor matainance (loose spokes) is a real wheel buster.  Steering design takes a lot of time but worth every minute.



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Nathan McCaw

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Yea, we spend most of our time on maintenance for the car, rather than practicing with what we have...

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electrathon


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I doubt the battery location had much to do with it. More likely steering geometry. On a long smooth corner geometry is not huge, on a tight cornering track it is a major factor in the outcome of the race. Some of the cars are so bad on tight corners they actually shed rubber from tire scrub.

Put your car on a smooth floor (the hall way in the school is great for this) and turn the wheel. Slowly push your car and watch the tires. If your steering is off you will very quickly see the tire scrub and the stress it creates.

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electrathon


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I usually try for about 30% of the weight on each front wheel and 40% on the rear.

bd64 wrote:

 

I think % foward weight is an extremely important factor in design.  Too much foward weight will brake motorcycle spokes, that along with poor matainance (loose spokes) is a real wheel buster.  Steering design takes a lot of time but worth every minute.

 



 



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Nathan McCaw

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Ok, thanks. I'll try it. Yea it seemed like we broke the most spokes on tight corner tracks, such as Eugene, and Mt. Hood Community College...

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bd64


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56% to 58% foward weight on a 72 inch wheel base works well.



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Nathan McCaw

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What would I need to put in the front of my car to make it 56 to 58%?

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bd64


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Your Butt, move it foward or aft as needed.

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electrathon


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Sort of funny, Eugene and MHCC are not tight tracks, Wait till you see Lacy this spring.

Moving your ballast weight is the easiest way to adjust forward to rearward weight.

Nathan McCaw wrote:

Ok, thanks. I'll try it. Yea it seemed like we broke the most spokes on tight corner tracks, such as Eugene, and Mt. Hood Community College...



 



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Zaine Stapleton


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A clicking noise from the spokes while driving probably means they need to be tightened up I'm guessing?

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Nathan McCaw

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Are they changing the track at Lacey?

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electrathon


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No, as far as I know, it will be the same as the last few years.  The back side has claimed a few cars over the years.

Nathan McCaw wrote:

Are they changing the track at Lacey?



 



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Nathan McCaw

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Yea I know... that back corner is not very forgiving for most cars, espesialy when the track gets wet.

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meangreen


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I use double-wall alloy rims. Compared to single-wall rims, they are a pain to get tires off & on, but they don't flex as much and therefore are easier on spokes.

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Jim Robinson
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What we have found is that one of the biggest things is maintenance. Between each race I have my students go over their wheels and tighten their spokes. I have raced the same rear wheel on my car for 3 years asnd have not broken a spoke yet-but I tighten/check my spokes before each race. As stated above car design also is critical. We try to have about equal weight on each tire. Willamette uses moped wheels for the front and bike wheels for the back so are design may be a little different than others. We usually have one battery in the front and the other in the back. The cars with two batteries in the back tend to break more spokes on the rear wheel. As Jim said double wall rims also helps a lot.

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bd64


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While equal weight on each wheel sounds good and even recommended in one of EA's handbook, there is much more to getting the balance of a car right. Foward weight is dependent upon wheelbase and many other items especially the type track you are racing. A static equal weight distribution is much different than a dynamic equal weight distribution. In a hard left corning situation, weight is transfered forward and right meaning the right front wheel and tire will under go much more stress than the rear or the left. If you add a bump in the corner, equal static weight will likely get loose to the point of out-of-control or make you corner so slowly that you will end near the end of the pack unless everyone else makes the same mistake.

Yes, wheels require constant maintenance and well worth the time spent. Remember races are won in the shop and lost at the track.

-- Edited by bd64 on Wednesday 20th of January 2010 03:02:40 PM

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Zaine Stapleton


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It's not always with where the weight is, there are other aspects to electrathon cars that need to be kept in mind as well.

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cory991


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Weight distribution doesnt seem to make much difference as long as it is in between the axles
and tward the center as much as possible.

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Cory Morris
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Nathan McCaw wrote:

It seems like after every race we have to replace at least three or so spokes... What can I do to limit as many broken spokes I can?


My team had a 48 spoke wheel that for some reason got a vibaration in it and all but 3 spokes came loose. The nuts that hold them to the rim all came out. Thats why I dont go with spoke wheels. I get mine made out of alluminum

 



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Cory Morris
Kyle Keenan


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We use thread locker on our spokes, if it's good enough to hold two-piece rotors on the NSX at 150mph, it's good enough for the e-thon car. Adds a few grams of weight but hey, it works. We still check them after every hour of use with the car. It takes only a min or so, so why not?


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Nathan McCaw

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Thatnks for all your input guys, I'll see what we can do.

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Vic


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We have a trike set up on our car with the batteries in the back and the drivers butt just about  the middle of the car. 
On our very first race we had no problem with breaking spokes but we did tip it onec in each race.
We have the wheels mounted on a plate than can be adjusted for camber and toe.  We shimmed the bottom of the plate with 5 fender washers and have had no problems with stability or wheels.  In a turn the force pushes down on the tire with very limited side force.
USF has a cycle car and they have quite a bit of camber on the front wheels.  No problems with wheels and they are very quick thru the turns.  Their batteries are mounted in the center, one on each side, like saddle bags.
You do need to keep up with wheel maintenance or it will all go to %@#$%.
 

Vic



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jakeb2011


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I think it has to do with your center of gravity, Wheelbase and weight of your car for breaking spokes. Its all about the design of your car. We've never had a problem with our spokes or tire wear cause of our wide wheel base but it only hurts you on cirlce tracks (which we do half the time).

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bd64


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ry%3D400


This is a wheel that we have used for many years now an it is extremely strong with excellent braking abilities.  It is a highbred that we made,  70s honda street 150, 160hub and spokes with double wall aluminum bicycle rim.  They will take anything other than a direct hil to a concrete curb.  They are heavey but good aero wise.  No rotor or caliper sticking out in the air.

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fiallok


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From field experience improper truing ie overly tight spokes can also contribute broken spokes

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