eR1c

iTrader: (2)

I've been using nylon bearings ..I may have some metal sealed ones new at home ..will have to check. BUT, sounds like some more work on the Mini is in order.

thanks guys-

Granpa

I can tell you've outgrown the level of advice I dispense-----like I said, it's for the newer guys and not the Pro's like you. No sarcasm meant in the Pro's comment, but for the level of your expertise.

The reason I say this is in Step 5 of the procedure I outlined for a relatively inexperienced guy, I say to adjust to 90 with the sub trim of the TX. I put some time and careful thought into that post and in essence you said it was bull shit and then didn't bother to read it. That's not fair and some "newbie" may decide based on your comment that don't bother cause you can fix it with the TX. That's misleading and careless.

If you don't read my advice, don't comment. If you do, read the whole thing. Let's try to help the guys who might read this stuff.

Granpa

Nylon shield bearings are okay as long as you don't try to eliminate the grease. Here's the problem----the degreasers, at least those in my experience, cause the seals to swell and make them drag a bit. That's why the metal shielded bearings. You can clean those.

I keep some metal shield bearings, good ones like from Boca, for racing. The rest of the time I just use $1 ones from places like Avid and throw them out when they get rough. Those are nylon shielded

axle182

iTrader: (18)

+1. This is why the incorrect information must be corrected. Sure there are ways to "take the easy way out" to do something, and when pressed for time we all have at one point or another. But unless the person asking for information requests the "cheapest and easiest way regardless of the end result", you cant continue to argue with the correct way to do things. Geometry PROVES that having the servo horn at 90 deg to the steering arm is the correct way to set your steering, due to equal steering throw left to right. This isn't an opinion. An opinion is "this works for me".

On bearings, I have always used the cheap metal bearings, removed the grease, and used a little Elf high speed oil. They last a decent time and aren't expensive to replace. I have 1 or 2 of each size in my RC box, to replace in an emergency.

Also spend time to ensure your not pinching the wheel/hub assembly when you attach the wheel. make sure you have at least one small shim between the hub and the bearing. Little things like that can make sure you have minimum friction on the rear wheels.

tony gray

iTrader: (7)

MYTH - BUSTED

from rc-mini.net several years ago...

There has been a lot of discussion lately regarding the C rating on batteries, and how the higher the C rating the more current the ESC and motor will use which is then mean to be a huge advantage on the track. People keep clamouring for the latest battery, sure that the extra 5C will give them an advantage… But will it?

This argument already has a serious flaw as it completely dismisses that fact that the speedies we are limited to using, have a 25A and 35A continuous current ratings, with burst ratings of 90A and 190A respectively. Which implies that the most current you could sustain through the speedies would be 25/35A. Straight away there's an issue there.

Looking at the most popular batteries at the recent Victorian State Titles:



Harris 3200 20C 20 * 3200 = 64000mA = 64A continuous

Team Orion 3200 Carbon 20C 20 * 3200 = 64000mA = 64A continuous

Peak Racing 3200 Carbon 20C 20 * 3200 = 64000mA = 64A continuous

Team Orion 3400 Carbon 25C 25 * 3400 = 85000mA = 85A continuous

Yeah Racing 3200 20C 20 * 3200 = 64000mA = 64A continuous

Looking at the speedies and the batteries we are using it's easy to see that the batteries are already capable of supplying more current then the speedies can handle continuously. Logic should then kick in and say that since everyone isn't thermalling, nor are the heatsinks on the speedies even getting warm after a 6 minute run, that we are not using anywhere near the current rating of the speedy. Even when running outside on the hottest February ever, when the temperature got to 46 degrees (this was during Black Saturday in Victoria) we ran the ESC for 1000 laps (Wodonga Mini Enduro) and although the heatsink was hot to the touch it was no where near thermalling.

Now just to try to see if what we believed was really true, we decided to make absolutely sure by actually monitoring the battery usage during actual races. Below is a table showing the results of 2 race meetings, the Victorian State Titles, and the Warm up race the weekend before.

As can be seen in the table below we have summarised the data from each run over the two race meetings, and we can see which pack was used for each run, plus the maximum amps recorded, the average amps used per run, maximum voltage, minimum voltage average voltage and the runtime.



Before we begin interpreting the data, some background on the races. The Warm up race was a race where I was trying to find a good setup for the car and was not really happy with anything that was happening. The car was handling really badly, and was very difficult to string consistent runs together. At the Vic Titles the car was great, easy to drive and just worked, the driver a couple of times left a bit to be desired - but overall I would consider it a good race meeting.

Looking at the peak amps data we can see the highest was in final 2 of the warmup race where the peak amps reached 42.3A. Looking at the graph below it can be seen that the 42.3A was only reached once, probably as a result of a coming together with another car on the track. The only other 2 peaks in the chart only reached 32/35A which is considerably lower, and more consistent with the remaining results



Analysing the rest of the results it would seem values of 28-35A would seem to be the expected peak current for the ESC/Motor system chosen as the control for our mini class. Looking a bit further, the average current draw is about 1/3rd that of the peak current which would mean the constant current draw from the battery would be a lot less then the peak current.



Breaking it down a bit further we can look at the graph below which shows the highlighted gray area representing a full lap of the track. We can see that most of the time the graph has short sharp peaks indicating the burst in current draw on acceleration, and then longer troughs where the acceleration has taken place, and speed is just being maintained. On a small tight track it would be that the average current draw could increase, but only marginally so.



From all this information what we can see is that the Mini with the Hobbywing ESC and 13T motor combo is drawing much less current then even the 20C batteries are able to easily continuously supply. Another interesting point is that there was no real significant difference between some packs that were nearly 2 years old, as opposed to some that were brand new. Yes, there are differences, but those differences could also be attributed to any number of factors anyway, not just age. And the differences are so small as to absolutely not represent any sort of significant, provable trend in any way. Thereby also effectively destroying the 'it's better to have new packs for a big event' myth as well.

So, what's the bottom line? Well, as Jamie and Adam are fond of saying on the tv – MYTH BUSTED. The whole contention that a higher C rating gives you more punch is complete rubbish. Yes, in a faster car with a lower turn motor it MAY make a difference, but in a control motor class such as Mini it makes no difference at all. There is simply no evidence to support it. At no stage does the amp draw even come close to the continuous rating of the lowest C rated battery (20C), so having a higher one will make no difference at all.

sakadachi

iTrader: (1)

Hummmm? Wait, I never stated your post was BS. I never argued that your approach was wrong; I even encouraged that there is nothing better than a completely square and perfect setup, but my comment was is it really necessary to go that far when a servo horn doesn't even align perfectly from the getgo, and at the end of the day, the approach I posted works just as well?

That's when I asked about the nerdy scale.
I don't even get a reading on the nerdy scale according to monkeyracing..

eR1c

iTrader: (2)

...bearings,

Thanks for the helpful advice (Granpa, Sakadahi and Axle 182).

I have been using Nylon bearings and have been trying to clean them (blast with air, then regrease). Guess this is not good. Doh! Going to switch to metal sealed bearings. Also the advice about using shims ...I have not been doing that for my Mini ...but will try it out. This is super helpful info (why I love these boards)!

sakadachi

iTrader: (1)

Interesting find. Tell that to all the hobby shops that sell high discharge rate batteries of no good, huh?

(just in case: Tony, I am laughing at the stores with you, not at you. Thanks for the info!)

sakadachi

iTrader: (1)

I've tried several different methods but it took a lot of motor spray and time to get it back to where a new one was. Even so, the balls wear anyway and was not worth my time.

The amount of spray I had to use did not economically make sense either, so I consider ball bearings a wear item like tires, and just replacing them.

Amazon has the nylon bearings going for like $10-11 for 10pcs.
A can of motorspray costs me about $10+ shipped. I rather just buy new bearings.

sakadachi

iTrader: (1)

Since when is the setup I noted "incorrect"? That's how the owner's manual shows how to do it too, are you saying the owner's manual is also incorrect?

sakadachi

iTrader: (1)

Everything sakadachi posts =

INCORRECT!

eR1c

iTrader: (2)

guys, guys, guys...

hesitant to get involved, but just want to remind you all that we are grown men talking about toy cars. Let's take a deep breath and go easy on each other.

Not taking any sides here, but you all (including Sakadachi and Granpa) have provided me great advice that has been extremely helpful. Sometimes the info I've received has worked for me and sometimes not. Regardless it's all been helpful as it would have taken way longer to figure out on my own, nor am I sure I would have discovered various solutions or things to try. We are all here to help each other with what we know, believe to be true, and have discovered. Looking at the cars on our track, our top 3 driver's cars are setup differently yet they are all very close to each other in performance. I take that to believe there are different ways to get to the end result and various setups work for various drivers.

that's all I have to say, ...you guys are my friends even if I've never met you in person. Would hate for this to escalate further.

monkeyracing

iTrader: (10)

Wow. Big letters.

Thanks for posting that again, Tony. I've got that somewhere in the archives from when i downloaded the entire site. Did you know you guys had 2500 photos on that thing?

axle182

iTrader: (18)

Well Geometry is proof that your way is incorrect, as is the M chassis manual. For the servo horn to have the same effect on the steering linkage, left to right (IE move the steering linkage the same distance), you must start at 90 deg. If you don't, for the same rotation of the servo left to right, your steering linkage will NOT move the same. Yes the manual is incorrect. Read a TC manual, they put the horn on at an angel, precisely for this reason. The M chassis has the servo horn square to the servo for simplicity reasons. They also supply the kit with terrible tires. This doesn't mean you can argue that the kit tires are the best.
While I feel I know a lot about RC, I am always here to learn, and I have learnt so much from contributors like GP, Monkey, and Tony. Tony's website was the best mini site on the planet, and I learnt so many great things from it. I hope I have been able to give back too! Please stop taking these discussions personally, this isn't Sakadachi's M chassis thread, this is a public thread.

Granpa

Here's my point. Since you didn't really read my post, that's what I said. I said to use the the sub trim to adjust to a perfect 90. The implication was that most servo horns,as you put it, won't come to 90 just use the sub trim. What I wanted the modeler to do was to spend a little time with the servo saver insert and try to get it as close to 90 as possible so that he didn't use much more than 10 points of sub trim.

Sure you can adjust the turning radius with end point adjustments and so on. you can use all the short cuts and make the car run straight, turn the same amount etc, but you still wind up with a car that's pure shitze.

Like I said, my advice is for the newer guy and not for the Pro's. If what I posted will give the guy a "square" car, leave it alone. All you do with short cut advice is to confuse the issue and encourage sloppy habits. Pro's like you know what you can short cut and what you probably shouldn't.

This is a personal preference, but I save the shortcut radio adjustments for temporary things like steering and throttle trim. I don't get off the drivers stand for example and adjust the linkages-----I'll use radio trims, but then I'll check the car over physically later. If it's more than a few points, I get off the stand, take off the body and go over the car. I know my car is square, so I'll know what to check and so will anyone who has taken the time to build a square car. This is why you won't see short cuts in my advice.

Now, I don't think I'm better than anyone cause I run at the Tamiya track. I usually post that as a disclaimer cause if the guy I'm posting to is running on a postage stamp size indoor carpet track, what I'm saying may not be valid for him. That's all period.