Racing brushless 1/8 scale

[neweuser]

Originally Posted by Bomb-Proof

I made one for my racetruck, dual motor brace. :027:




No way you could flex 5mm carbon that size, a 50mph headon into a wall wouldnt phase it. Get the good stuff, quasi layed, 100% carbon and its not going to flex.

That's nice BP, how about a pic of the whole thing! :027:

[glassdoctor]

I use CF for my motor mounts.... two layers of @3mm sheet.

[sleebus.jones]

Hah! I stand (or sit!) corrected.

/me shuffles off to the corner to put on his dunce cap

Sleeb

[glassdoctor]

Originally Posted by sleebus.jones

Hah! I stand (or sit!) corrected.

/me shuffles off to the corner to put on his dunce cap

Sleeb

LOL no need for that... I wouldn't do it unless the CF is like 1/4" thick. I did it because I had some and it's easier to work than aluminum, for me anyway.

[neweuser]

Myself, I don't "make" my own CF, but when I buy sheets, I like to work with it too as it's easier to cut and shape.

Ok, so here is where I am now. I think that it is race worthy at this point.



I got my order from Mike. I got the Kyosho spur, the 8L motor, a 16T pinion, and the heatsink.

The first thing I did was drill and tap the heat sink 3X0.5mm and mounted a 40mm 12v fan to the motor. It's wired directly into the battery lead going to the ESC. Man, does this thing move air. I managed to get the spur to fit, after some fine tuning on the lathe. Dropped the whole thing in and ran it on 3S Lipo. MUCH faster than the 7XL. It's not stupid, but it's fast. While running I kept "feeling" the heatsink to check the temp and all seemed OK. When the battery dumped, I just happened to reach under and feel the motor itself. Scorching hot, although the sink was only barely warm to the touch (I did use thermal compound). Pulled the sink off of the motor and there were on two skinny lines of thermal compound on the motor. The heatsink doesn't fit right. That kills me, because I could have just bought two clip on heatsinks WITH the fans for about half the price of the Monster sink. I had to clamp the sink to my drill press and I hit it on the sides of the inside with an end mill and removed material until I got a good fit. Reinstalled everything and all is good. I can't wait to see how this 8L runs on 4S.

To test for race worthyness, I let my 8 year old put a pack through the buggy. He cartwheeled it down the street, hit a mail box post, rolled it a couple of times, and for the grand finale, he jumped the curve and smacked a utility pole. Nothing moved. It's all good.

All I have to do now is clean up the wiring and it'll be done. I had to laugh. My son says that it's more fun than his little rc18t. He did make one keen observation. He did notice that the buggy didn't break. I think I'm going to have to pick up an Ofna MBX R2 or something. Those things are dirt cheap and parts are cheap too.

On a side note, I found out that my batteries will be here on the 13th. A hair over two weeks to get them. If I had known that, I would have just ordered some more expensive batteries that would have gotten here quicker from someone else. The guys at Maxamps are great guys, and they will take care of you when things go wrong, but geez. I don't want to sound like a weinie, but I've gotta have it NOW!!!

Now...some gearing questions. I'm figuring that 14T will be good for the 7XL on the track. Right? Will this leave the motor under loaded? I'm asking because running it on 3S, the motor was heating up, but the esc was always cool. How about the 8L? Any suggestions?

Bomb-proof,

I like your style. I've always said that too much is better than not enough.

As for the CF, how thick should I get it? That .09" stuff looks good. I hope that I can mill this stuff. I'm hoping to make an adjustable tray to accommodate batteries of varying width. I'm going to get on line and try to find someone that can overnight me some Tanic or Flightpower packs. I really want to race this weekend.

glassdoctor,

What sort of tools do you use to work cf? What do you use to bond the pieces? CA?

[glassdoctor]

Yeah... the stuff I have is 3mm so I use CA to "laminate" it. I have basic woodworking and shop type tools. Band saw w/metal blade... various sanders, drill press, dremel, stuff like that. It does do a good job dulling drill bits and saw blades. But it sands easy with a benchtop disk/belt type sander. Just watch the dust... you don't want to inhale it... it's nasty stuff.

I think two layers of .09 would be pretty good.

I hear you on having to wait on orders... I like to know up front when I will get it. About a week is all I can take when I "need" something, lol...

Would it be better to do a laminate with two layers or a single layer of thicker CF? I'd think that two layers would be better, but what do I know?

[glassdoctor]

I don't know either really... the CA laminating works pretty well but I have had it start to separate on one of mine. But I just put a screw through the layers in the corner to give some strength and it's been fine. I have a screw tapped into the mount from the chassis so the screw "splits" the two CF layers... so a screw is needed there.

The stuff I have isn't the classic CF pattern look... it's seems to be a little heavier and it doesn't have the cross weave pattern. It has the look more like molded graphite. I'm not sure if better or worse than the other stuff.

Mine is scraps from a local company.

hey... check out the video I posted in my "my rides" thread... it's up now!

[pinolelst]

Originally Posted by AAngel

Would it be better to do a laminate with two layers or a single layer of thicker CF? I'd think that two layers would be better, but what do I know?

Assuming good quality a single layer should be stronger since there's fiber crossing every possible shear plane.Like GD said...he's observed delams in his laminations

pinolelst

I like using one thick single peice, because I dont trust my laminating as much as the pros. :027:

[Serum]

CA is not as good as the way the CF plates are baked together.

I went ahead and ordered the .125" thick stuff. That should do for the battery tray. I ordered two 1 foot lenths of angle. One is 1"X2" and the other 1"X1". I'm just going to epoxy the two together to make a tray.

I ran the 8L tonight on 3S Lipo. It was pretty fast. I'd guess about 40 give or take a bit. Motor didn't over heat. ESC was fine, but my battery started smoking. It got HOT. I think the smoking was from the shrink wrap melting. I let it cool, balanced it and charged it. I didn't notice any puffing. So...8L on 3S = too much current. I switched back to the 7XL and ran that on 3S with a 16T pinion. I noticed a bit of a drop in motor temp and it ran fast. Fast enough the be one of the fastest on our track. I'm guessing that 4S with a 14T pinion might be about right or a bit too much. I should have listened to you guys and gotten the 1800 kv motor. I'm just afraid that the 7XL is going to be undergeared when I gear it for the track. Maybe another motor is in order. Perhaps a 9XL or maybe an 8XL. I've gotta think about it.

[Serum]

i thought i am using .062 for the trays, .125 is beefy! (and hard to cut.) if you work on CF, make sure to wear breathing and eye protection! it's a danger for your health.

Serum,

I may be off on this, but what I plan to do is to only have to make two cuts. I ordered angles, so all I'm guessing I'll have to do is to cut two lengths as needed and sand two edges to accept the epoxy. I was hoping to "wet" cut the CF using an abrasive wheel and an air powered cutting tool.

I weighed my buggy with a 3S lipo in it today. It came in at 7.5lbs. With the 4S2P 6Ah pack, I'm guess that it'll be right at around 8 lbs. That should drop a bit with the addition of the carbon fiber tray. I want to go 8Ah or even 10Ah, but am concerned about the weight distribution and it's affect on handling. I don't want to go experimenting too much, because that could make for some expensive experimenting.

I ran the buggy again tonight and let a friend of mine drive it. He wasn't used to the acceleration. About 1/3 the way down the 160' straight, he was up to speed and didn't expect it. He smacked the wall and sheered the pivot balls right off. I've never seen anyone sheer pivotballs like that. He must have been cookin'.