New hi-speed project

[MetalMan]

Originally Posted by BrianG

Not to throw a wrench in all this, but what about this ESC: http://www.hobbycity.com/hobbycity/s...idProduct=4691

12s @ 100A sounds nice to me. And since I'll be running 9s, it gives me a little headroom on voltage.

All the user reviews seem to think highly of it, and it doesn't need a pistix adaptor. Warranty/service might be an issue, but for the price, it's hard to pass up!

I've had good luck with it in my MT2 and a 4130 outrunner on 10s1p A123, geared for ~75mph. It runs cool, too bad the same can't be said about the motor. It's just too bad it takes up so much space!

[BrianG]

Not much progress really. Just made a new servo bracket to push the brake servo out further to allow room for the motor and pinions. Had to make a new linkage as well since the stock one was too short. Also got my 1515 2.5d motor in.

The pinion on there is an 18T from the top shaft of an emaxx tranny to give me an idea of the room I'll have (plan to have a 20T pinion on first gear).



Now I think I'm gonna hit Mike up for a motor mount...

[lutach]

Originally Posted by BrianG

Not much progress really. Just made a new servo bracket to push the brake servo out further to allow room for the motor and pinions. Had to make a new linkage as well since the stock one was too short. Also got my 1515 2.5d motor in.

The pinion on there is an 18T from the top shaft of an emaxx tranny to give me an idea of the room I'll have (plan to have a 20T pinion on first gear).



Now I think I'm gonna hit Mike up for a motor mount...

Looking good. I hope to see a nice video of that beast flying.

[BrianG]

Originally Posted by lutach

...I hope to see a nice video of that beast flying.

Me too!

[BrianG]

Not much, but a little progress. Was away on vaca in SoCal and the previous week was pretty busy...

Anyway, got Mike's mount in the mail. Fits like a glove, but does require you to mod the stock spacer a little. All you have to do is trim the side edges. Really, only one really needs to be done, but I did both for consistency.



Also got the optional 44T 2nd gear along with Mike's 2 speed pinion adaptor and the 20T and 25T pinions. So, gearing will be 49/20 in first and 44/25 in second. Man those pinions are big! Was a little tough to get the mesh set perfect since the pinions are too large to fit the hex wrench in there to tighten down the motor screws. But I managed.

Also got the CC HV-110 ESC in as well. Castle said they would make a custom HV-110 for me so it was more like a HV-160, but we'll see how this one works first. If the ESC has issues, I'll spring for the added FET layer. The ESC will be mounted in the center for optimum wiring.

As you can see in the picture below, the side guards were removed. I plan to make new ones the correct width out of fiberglass. That should help undercar air turbulence as well as give me more room for the lipos, receiver, BEC, etc. Not sure yet if I want to mold the battery tray into those guards or keep it seperate, but the battery tray will be fiberglass as well. Glassdoctor was nice enough to give me a few samples of different fiber weaves to try out, so I'm pretty psyched. Just gotta get to Home Depot to pick up some lumber to make my tray molds and get my butt in gear...



I got a little anxious and temporarily hooked up an extra MM on 4s and ran it in the basement a little. All I'm gonna say is this thing will be fast! There was just a teeny bit of cogging, but I haven't updated the firmware on the MM yet, the wiring wasn't exactly optimal, and the gearing is kinda high.

[its me]

Originally Posted by Mod Man

Well, my TC4 is geared 1.8 to 1. That is geared for 150 mph wheel speed and I have no low speed issues what so ever. It just launches! It will tool around nice and slow or really launch with no cogging at all.

Oh, I get HUGE tire smoke even when the car is running 100 mph. You cannot appreciate high speed and crazy power to weight ratio untill you drive it!

Matt

Could I have a link to this build? I have been kicking around the idea of a TC4 but do not see to many people that build them?

[Mod Man]

Here's a link. http://www.rcgroups.com/forums/showt...=top+speed+tc4

I do not want to hijack this tread, though. You can PM me with any questions. I can shoot you my number too if you would like.

Also, Nic Case is a friend of mine. We have talked about the TC4 ALOT. Between the experience of the two of us, I doubt there is anything TC4/top speed related I cannot answer (and yes, there are a few MUST DOs with the TC4 that are needed for top speed running).

So, back on topic;

The HV110 will be plenty. Going with the custom HV160 is not needed. I pull close to 130 amps on 12S through my HV110 without any issues at all. It just runs and runs and runs. Amazing ESC. Now if they can just give the darn thing decent brakes.............

Matt

[BrianG]

Why would you want electrical brakes for a vehicle like this? IMO, the back-EMF would be too high (especially considering the high motor rpms, high gearing, and vehicle weight) for the batteries...

[lutach]

That looks good BrianG. Hope to see some numbers soon. I'm thinking of some MOSFETs to replace what they currently use and I found some amazing ones. I just have to see if I'll go with the 75V or a 60V one and if Patrick is willing to go with it . The current MOSFET is a Si4470 (60V, 12.7A cont. and 0.011ohms). My options looks like this: (75V, 45.8A cont. and 0.0133ohms), (60V, 30A cont. and 0.0092ohms). I might replace the MOSFETs on my Kontronik Jazz 40 first just to see if it works out. I know there are other things to consider, but it's worth a try.

[Mod Man]

There are 3 main reasons why I run electric brakes on my car;

#1 Space. Where is there room for them?

#2 Weight/complexity.

#3 Time to make and work out the bugs.

Innitially I wanted to make mechanical brakes. But, I found the electric brake to be perfectly fine even the poor HV110 brakes. It just takes a little fiddling to get the setting correct in the ESC.

The car stops wonderfully. Nic Case struggles with braking more than anything else. I have never had a problem getting the car to stop.

However, that being said, if I already had a car with mechanical brakes, I would definately use them.

Matt

[BrianG]

Yeah, for your vehicle, elec brakes probably works ok, but this is a relatively large and heavy 8th scale, and I don't wanna push things too far (like I'm not attempting to do that anyway ). This is the first conversion where I'm using mech brakes, but that's because all the other ones are 14 NiMH cell, 4s, and 2s setups.

[Mod Man]

I agree.

Oh, one thing with electronic brakes, if you have an electronic glitch, it is possible to lose brakes. It has happened to me twice. I had to stop by weaving to scrub speed, then turning hard to spin the car. Not good.

But, that was with my MGM ESC. The HV110 has been alot more stable and glitch free.

I will say, each time I break 100, I worry about stopping. Ideally I need redundant braking.

Matt

[lutach]

Originally Posted by Mod Man

I agree.

Oh, one thing with electronic brakes, if you have an electronic glitch, it is possible to lose brakes. It has happened to me twice. I had to stop by weaving to scrub speed, then turning hard to spin the car. Not good.

But, that was with my MGM ESC. The HV110 has been alot more stable and glitch free.

I will say, each time I break 100, I worry about stopping. Ideally I need redundant braking.

Matt

Have you given those air brake systems any thought?

[Mod Man]

Hmm, haven't thought about that!

I have thought about a spring loaded system that would lock if the ESC failed.

Matt

[BrianG]

lol, or little parachutes.