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-   -   The Science of weight (http://mini-zracer.com/forums/showthread.php?t=1136)

Mondo 2002.01.28 01:03 PM

The Science of weight
 
I see many Threads from Members concerned about the 'extra' weight and performance loss people believe they will suffer from replacing standard parts with alloy parts.

It seems as if some Mini-Z owners believe they are managing super models and have to ensure that no weight is gained under any circumstances.

A prime example of this was a comment I read where a Member believed that is he fitted an alloy steering bar, it would 'slow the steering' response down because of the 'extra weight'!
A second example was the belief that an alloy heatsink motor clip (that fits onto a standard motor mount) made the car back-end heavy. Is this fact, fiction or sheer paranoia?

Personally I am yet to experience any drastic performance loss through weight gain when using alloy parts.

I have used my favourite 'cocaine-scale' reference. The 'cocaine scale' as I term it is actually an accurate scale that measures between 0-50 grammes on .01 gramme incriments. It's an uncannily accurate measuring device.
Perhaps I should find out where I can use one, my local pharmacist (AKA drug store - although that term would get the police investigating in England) or some other establishment that does precision measurements.

If I can get my paws on one, I will take the time to measure every alloy hop up against the standard part.

I know a lot of Members have alloy parts on their cars..
Any valid comments?

Mondo
__________

Joe 2002.01.28 01:12 PM

Only use your alloy wheels for display purposes. They are much heavier and so increase rotating weight which dramatically slows your car down. It also increases the load on the motor by a fair bit!

Machritis 2002.01.28 01:58 PM

Weight
 
I'm not really an expert in this subject, through some common sense and logic, it doesn't really seem that the alloy parts and extra weight are going to make such a difference on performance. Yes I have heard that a lot of people say that it slows the cars down, but is that a psychological experience?

The car itself is really light, and I'm going to make some measurements on the cars today... I don't have to most accurate scale, but it'll do. Anyway, from my standpoint the stock motor provides the wheels with enough power that they can spin out on most surfaces I have tried, (except for some rubber sticky kitchen mats)... The car is working on such a small scale, that in some cases, such as mine, the weight helps the car, because it does not have enough traction to use the power of the motor in the first place. So if the wheels are spinning out, at all, that means somewhere you have excess power, and if you don't have enough traction, that power goes to waste, so weight can play a part in helping the performance in the car, instead of hindering it.

Then again, if you are running on a sticky, no-slip type surface, and your wheels don't have the ability to spin out, then the extra weight will slightly slow the car, but I don't think it would be much of a difference, unless it is a substantial amount of weight. So of course that means the most power is given to the wheels when the car is in the very edge between slipping, and traction...

But of course that's just my view from a logical stand-point, I haven't really tried adding a lot of weight, but trying with and without the body can give some idea what will and can happen. So I hope that's useful, and correct anything that's wrong, because I, of course, may be.

-Machritis

jcostantino 2002.01.28 03:01 PM

Mondo.... are we going to have to arrange an intervention for you? Do you have some "habits" besides your Mini Z's? :)

I would have to say that adding weight can be good on the Mini Z.

My Z with its ball diff, aluminum motor mount and triple oil shock setup has HUGE extra weight on the back end. BUT, for me it helps out quite a bit since I went to medium tires and hard front suspension and my car drives like a dream now. I could maybe use a few gramms on the front but I'm about to the sweet spot between over and under steer. It's hard to say exactally, but I can't be sure if the oil shocks themselves or the weight of the metal on the back is better for my car's handling.

Jeff

Russ 2002.01.28 03:58 PM

about the alloy wheels...no doubt in my mind that they're heavier, it's just that it's very unnoticeable how different the weight is between the alloys & plastics. I guess every little bit counts, but they're not any heavier to the touch at all.

Ken Mifune 2002.01.28 04:59 PM

Add all the aluminum parts possible.
Plus add: bearings; ball diff; turbo; triple shock...
It's bound to add up to a hefty weight difference compared to the stock-Z.
It's academic, the density of aluminum & steel compared to polystyrene & nylon is a big difference on any scale. And it's logical to say that more weight means slower accelleration, but which parts improve lap times.

Glamour or performance? Sometimes you get both in one part.
It's kinda like Wedge's LEDs make him go faster.

mini-z 2002.01.28 09:17 PM

I agree w/ Russ, the alloy rims don't have any noticable affect for me, and I'm running a 360 body that is 70-80% lighter than any other body. This body, however, makes a HUGE difference!

Draconious 2002.01.28 11:00 PM

Its been noted before, but standing weight of the plastic and alloy rims is basicly miniscule... however rotating mass will be more noticeable, however this could have a good and bad effect, rotating mass can act like a gyroscope if its propperly balanced (bearings), its also putting the weight to the ouside and low, cant get it much more outside then that, so if you need it there then its good, but it can also destablize the car that way too, but can also stabilize it ;).

It can also require more OOMPH to get it going...

I would say you loose 5% top end (how often do you realy get to top end!?) and gain 5% stability.

You basicly have to try it, if u like it use it, if not buy some more parts ;). A part that knocks 2 seconds off of one drivers lap time, might add a minute to another drivers...

aesch 2002.01.29 05:29 AM

The analogy I'd use is the cross country mountain bike scene about 8-10 years ago when they went insane and shaved grammes off everything. Had the WoW factor of having the lightest gear, which meant less weight to pedal around. After a year or so, people started realising that all those "light" parts broke relatively easily and they all went back to slightly heavier parts. Sure, a few more grammes here and there, but made them sooo much stronger and lasts longer :D

Let's not speak about the crazy downhill mountain bikers where the bikes weigh almost as much as a motorbike, but still break. Wouldn't want to ride one of those things uphill though...

Aesch :)

Draconious 2002.01.29 12:11 PM

I have a mini-Z chassis that has the bageezes shaved out of it ;)... some one traded me a model body for a chassis and perfex controller... but I only got the chassis... then they disapeared. It will now cost me like 20$ to re-aquire that body in a new kit.. oh well, I had hoped to see the mustang body on here (was in November '01).... well this chassis I got had holes drilled all over it, so its kinda useless... all I was able to use from it was the battery clips (note the chassis used is pictured on that stupid discharger picture I posted a while back, but I kinda hid the holes ;) hehe... well it had holes in it and was useless any way, so I put BIGGER holes in it, just to see how far I could go... It would have worked, but vibration on my dremel caused the nose plate top piece to break while I was making it thinner... and had they put the holes in better places I could have made it work realy good.... its realy ugly cuz of the drill holes though. swiss cheese...

Mondo 2002.01.29 07:14 PM

Comments so far..
 
Guys,

Thanks for the comments, all but one have been valid and make sense.

As for the 'alloy wheels for display purposes only' is concerned, well, Joe, no offence, but you hold the wooden spoon award so far..

Ken's comment also makes sense, gain a 'little' weight to add to handling performance and you'll benefit from those parts. This increases lap times (In theory :D if the driver can drive!)

Mini-Z shed lots of weight using a Lexan bodyshell and this counters any weight (but not all) gained by the addition of alloy parts. Good points, lose some weight and gain some with the hop-ups.. :) Of course the CG is lower with a Lexan bodyshell too..

aesch's comparison with the mountain bike is also a good reference. Example, an alloy motor mount weighs perhaps 5% more than a standard plastic one. The alloy mount dissipates heat better and the motor runs cooler and more efficiently. A performance gain that probably does justify the few extra grammes.

Jeff says he had a 'huge' amount of weight added to the rear of his Mini-Z. He attributes this to his triple coil over oil shock, ball diff and motor mount. (bearings too I guess..) Jeff states quite clearly that the added weight pays off.. This is the benefit of added weight, but Jeff did not state that all the alloy makes the car that much slower..

Machritis comments that perhaps the added weight could have a psycological effect on some Mini-Z owners..
I agree with that 100%.. :) A good comment..

Russ admits (as do I) that the alloy parts are heavier, but it's barely noticeable. I don't see Russ saying that the alloy parts are an Achilles Heel or anchor..

Draconious, the tinkerer himself mentions the gyroscopic effect and throws balance into the equasion. Two valid points most people overlooked.. Also, Drac mentioned his second chassis that someone botched while trying to lighten it by drilling it full of holes.
Is that amount of damage worth the performance gain? I don't think so..

Guys, the reason I've been focusing on the weight issue is the fact that so many Members carry on about weight as if it were a disease.
I think from the valid comments here, weight has it's advantages.
Some of the Members may remember Herman from the Philipines adding a few grammes to his 206WRC with Mini-4WD lead weights. He stood firm on the fact that this helped the Mini-Z handle better on the track he frequents.

As for those who want to freak out about weight as if it were a contagious disease, they are free to do so.
Unfortunately their beliefs are passed on to new Members who are told to avoid all things good, like alloy hop-up parts.

One thing I did notice, when it came to this issue being raised in the Mini-Z Science Forum, most replies were from longer standing Members.
Perhaps the Forum title is "too heavy" for most of the new Members :D

Thanks guys.. I think the point is proven, weight doesn't have to be a bad thing..

Keep up the faith..

Mondo
__________

Russ 2002.01.29 09:30 PM

Well, I am perfectly fine with my plastic parts, until I see the need for alloy in a certain area, such as rims and steering knuckles (broken parts from my webpage :)). After I break a plastic part, I will 99% of the time upgrade to alloy. I could live without it, but alloy just stands up better. As you add more and more alloy parts to your car, the weight does add up, just very slowly & in small amounts :) MyZ, stock, weighed in at about 150 grams, and now, with my alloy wheels, ball diff, alloy motor mount, alloy battery clips, bearings, shocks, turbo, yadda, yadda, it weighs in at just under 200 grams. So, they do add weight, just not a noticable amount per part.

jcostantino 2002.01.29 10:14 PM

I guess I didn't mention if the parts affected my acceleration. I suppose it does, but not to an extent that it makes my car ineffective.

I would rather have control over speed when driving on a technical track... I haven't even changed the stock motor or 6t pinion yet.

I did put the Z8 body on at the track today and drove around. The long wheelbase is really nice but the body has no problem going over the barriers (garden hose) so I need to devise a bumper system tommrow.

Jeff

Russ 2002.02.05 09:40 AM

1 Attachment(s)
How's this for lightweight?? LOL

butler 2002.02.05 09:48 AM

Hey Russ,

I have been thinking of drilling my Z the same. Did you notice an improvement? I think I would put clear tape over the ESC though.

Cheers,


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