[Cjtamu]

Since the HO Gang (myself included) seems to have a tendency to stray off topic, thought I'd start a thread devoted to wrenching on these tiny cars and maybe make things easier to find. They're a lot different than they were when I was first doing this shortly after electricity was invented. I'll start with a couple quick questions I have: 1) Pickup shoes. I see posts about shoe tuning or flattening shoes to get better conductivity. What are you looking for, just maximum contact patch? I assume you set the car on a piece of track and then just gently bend the shoes to maximize? After first making sure your guide pin isn't hitting the bottom of the slot of course; 2) Gear mesh. When I was breaking in motors I noticed I have a couple Mega G cars where the gears bind when the axle moves all the way out to passenger side of car. Both these cars pulled significantly more amps than the other two Mega G. I'm not sure how much axle play I should have in the rear so not sure of the best way to fix. Should I just press the spur/crown gear towards the left slightly and leave the play or should I actually shim the axle assembly so there's a little less play? Any rough measurement on how much side to side play I should have in rear axle? Thanks.

 

[Cjtamu]

You answered your own questions Cjtamu, and you're spot on.

I think the pinion under load keeps the crown spaced properly. It would be a problem if the axle didn't spin freely in your fingers and the gears were binding.

If I spin right rear they spin freely, spin left rear and you hit a point where it locks up completely because you're bumping the crown gear away from pinion. The other 2 MG cars don't have this issue. I would assume that in a left hand corner the weight transfer moves crown gear in towards the pinion but in a right hander it's moving away and that's where the issue would be. Were it to lock up the way it does by hand I'd be replacing gear(s). These 2 cars were pulling 250+ mah at 6V just sitting on a break-in stand, much more than the other two MG cars. And much noisier. I'm going to shim it in slightly, just trying to figure whether to shim axle or just move crown in. I'll look for Rich's tuning articles. I figure over the years he's probably answered, more than once, every question one could ever have about slots. I just have to find the posts LOL.
.

 

[Cjtamu]

Great little tool. Gotta make one. Lord knows I have enough Dremels and small screwdrivers.

 

[Cjtamu]

I've searched the forum looking for a comprehensive tuning guide for HO thread, no success thus far. Bits and pieces here and there. Is there a "HO Tuning Guide for Dummies"? If not, there should be.

 

[Cjtamu]

A comprehensive guide for H0 tuning .... giggle.

It would dwarf War and Peace.

Yes, but people would actually FINISH the tuning guide ha ha ha. I have a better than average understanding of vehicle dynamics. What I DON'T have is any idea what to do to get these little cars to handle the way I want them to. Don't have the variety of adjustments either mechanically or electronically that I'm used to. I'll just keep asking questions and see where we end up. Like , right now I have one MG+ cars that's just a dog compared to the other 3. These were all NIB cars. IME with tabbed can motors it's typical for some to run better than others. You can hear the RPM difference in this car with the wheels lifted. I'm going to take it out, spray, oil and put back in and see if that helps. Is there a good way to zap the magnets in this motor? Any other tweaks you can make to these?

 

[Cjtamu]

Thanks, @ RichD. House full of people next few days and as that car sits it’s a good one for the grandkids to play with. It’s going to be my sacrifice/experimenting car so I’ll tear into it after everyone leaves. Suspected might be magnets because it feels different when rolled by hand but I’ll look at the other stuff too.

 

[Cjtamu]

LOL @model murdering. I’ve cracked a bunch of tabbed motors in my time but never anything this tiny. I have 4 that run well, then this one that handles well but has no huevos. Actually turns good lap times on a 30’ish foot track, just no top end. I think I’m going to order a complete chassis then swap an aftermarket motor into this one and see what happens. Gear mesh in this car is excellent. Super smooth, very quiet.

 

[Cjtamu]

Thanks, MM. Love the Porsche. But I’d like to see the 2 ohm new car go! That must be one of those current eaters RichD was talking about 😁. Merry Christmas everyone!

 

[Cjtamu]

It opened up in my Google Drive. Could see your articles I’d looked at previously but not anything else.

 

[Cjtamu]

Thank you, sir. Little reading to do in my spare time.

 

[Cjtamu]

Boy, that was fun! I have a used short wheelbase MG+ car that came with a body I wanted and it’s my experimenting car. Finally got around to installing front axle and o-ring tire set and rear axle, gear, hubs and silicone tire set I bought a month or so ago. Put softer front springs in the pickups and left stock magnets in. It’s like a whole new car. I turned the AFX tri-power pack to the Expert setting and the car was plenty drivable on a 30’ track whereas stock car is not. Fast but very controllable, I could slide it on the insides and use guardrails on outsides. Can’t go WOT on my track but still a lot of fun. Might try the stronger magnets but pretty happy with it as is. Ran it for my wife a little while ago, pretty sure I’m about to do one of her long wheelbase cars next ha! Pretty sure most of those mods are available for the Autoworld cars cbwho, might be worth trying.

Is there a hub puller/press for front wheels or is it not needed? I have one to pull rear hubs and press hubs and gears but haven’t seem one for the front. And is there any way to clean these motors? I was going to use motor spray but theres no place to get it in. Tried sparing through endbell, no bueno.

 

[Cjtamu]

What voltage do y'all generally use with the MG cars? Finally got to drive one last night and it was a blast. I ran at 18.5 V last night and the car felt good. The modded MG+ also felt good at that voltage which makes me think I could run them against each other. Just want to be sure 18.5 isn't too much for the MG motor. Thanks.

 

[Cjtamu]

We found that with Mega G+ cars with some chassis the traction magnets can be lower in the chassis. Even if the magnets were the same strength not every car would have the same amount of magnetic downforce. For that reason we have a spec for the distance between the bottom of the magnets and the bottom of the chassis.

I was just sitting here wondering about that very thing. When I lowered my MG+ it stuck to the track great, but we ran my wife's tonight and it wasn't even close. I could feel the difference when I lifted them off the track. I ended up putting stronger magnets in hers and it now has a little more downforce than mine with stock magnets, but not a lot. I'll measure and see if there's a difference. Thanks for the tip.

 

[Cjtamu]

I pushed her magnets far as they would go before we ran her car. Could be just weak magnets, but I'm wondering about the distance because even with level 42 magnets her downforce is just a hair greater than mine with stock. Both are SWB chassis with the same body. Going to try to take a look at it this evening. That's a great piece of kit with the scale. Have seen the commercial downforce testers. The one track in our area has magnet limits so waiting to get out there and see what they use to measure.

Edit: RichD, do you have any tips for measuring from bottom of magnets to bottom of chassis? I don't have small enough calipers or ruler or anything to fit in there. Best thing I can think of is to take a small piece of cardboard or a toothpick and mark where it sits flush with chassis.

 

[Cjtamu]

Her MG+ car is very fast. The stronger magnets gave her just a little more downforce than I have in mine which makes for some VERY competitive racing! She's happy, I'm happy. Just looking into the reasons for the downforce disparity between 2 cars with the same setup to add to my own personal knowledge base.

 

[Cjtamu]

That's interesting, Rich. Everything else I've ever read says the MG+ stock magnets are level 30, and that includes BRS Hobbies website where they're selling the Viper Level 42. Mine came from HCS and I think Terry has something posted somewhere where he says stock is Level 30 also. Probably never know for sure and with all that's going on in the world possible they made a running change too. Both cars are super now and a ton of fun to drive. Enough magnet to drive it fast but not enough that you can snooze. +1 on tropical storms. We're about 30 miles from TX coast, might have seen one or 2 of them. Gotta find some way to pass the time. Sometimes something that you can do off generator power ha!

 

[Cjtamu]

Wasn't quite sure where to post this so figured this was as good as any. Has anyone made slot motors with cylindrical brushes? That was the last big thing with brushed RC motors. Broke in fast, less arcing and less maintenance. I'd have to go dig one up to verify but as I recall they were set in a 45 or 60 deg V.