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 :smile:). 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.

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?

Hmm, haven't thought about that!

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

Matt

lol, or little parachutes. :smile:

How abot an anchor? With a small chain. Maybe use a winch servo to retract it?

Thank you very much! Im drooling here :)
K back on topic- brian what speeds are you shootin for?

I'd like to get well over 100, maybe 130ish, but I can only get a calculated theoretical speed of around 140, but with wind/drivetrain drag, I'll be lucky to get 110. I probably could get a bigger pinion if I went with a single speed setup, but I want to retain the two speed for just playing around too. A single gear set up for high speed is a lot for a motor to pull considering the size/weight of the vehicle...

That's a 1515 right? Seems like a 1521 would fit if you're not sure it will have enough top-end speed. Also, on the brake issue- why not use both mechanical AND electrical? Sure you need a more expensive ESC since airplane controllers have crappy brakes, but you will never have problems bringing the car under control.

The 1521 will fit, but I was able to get my hands on the 1515 at a very decent price so... If you have a 1521 of a similar kv (1700) you wouldn't mind trading/bartering, let me know. :wink:

The mechanical brakes lock up pretty good. The linkage I modded allows me to adjust the "progressiveness of engagement" (if that made any sense) so, it should be ok. Even so, I wouldn't want to use elec brakes on something this large/heavy running at 10s. The back-EMF voltage would be too high for the lipos IMO.

TBH, I wonder if this ESC "regenerative braking" effect is what causes lipos to heat up even on lower voltage systems. Just on the bench running on 4s, I saw some pretty substantial reverse voltage spikes and negative battery current (which means current was flowing into the battery). If braking hard enough and depending on gearing, I can imagine ample potential for this "charging" current to be well over the recommended 1C charge rate. I'm seriously considering some type of transorb/voltage clamping device to limit the amount of voltage getting to the battery on all my higher powered setups. Basically, I would choose a device with a voltage rating about 1v higher than the max battery voltage. When the voltage exceeds this rating, the device would simply shunt the excess voltage to ground. I'd rather replace a $2 part every so often than shorten the lifespan on $600 lipos!

Good idea on the back EMF issue.

I have never had a problem in real life, though. The lipos can take sort spikes of high back current, but not long duration.

Matt

Maybe you're on to something.. ever since I did Nitro ---> brushless converisons with Mechanical braking... I have never had any heat issues at all....

Instead of a transorb, why not just use a zener diode with appropriate voltage/current ratings to protect the batteries? Seems simpler to me anyways and the diode will last forever so long as it can handle the current produced.

I guess my anchor idea is stupid.

I have noticed that mech brakes do seem to lower the esc temps quite a bit. I have a quark 80 airmaster on 5s in my tekno revo. It runs a aveox motor very well. I have a feeling that the motor is loaded quite a bit,maybe even slighly undersized, and it will get the esc warm, but it never gets much over 130. The quark air esc is nice as it does not require a pixstix, and stars just like the car model. No proportional brakes, but it has all of the other features.

Retro-rockets?

Yeah, whatever will work I guess. Even a transistor or FET could be used...

Wait a second, you were in SoCal and didn't notify us?!!?

One thing with mechanical brakes at those speeds is heat. Don't forget KE = 1/2mv^2, so stopping at 100mph creates 2.5+ times the amount of heat as the intended ~60mph stock top speed does. On my ~13-14lb Savage with dual front disc brakes and no rear brake the fiber pads were melting from high speed-only running.

Yeah, but the few days before I went, I was busy and forgot to tell everyone. Sorry. Regardless, it was a really packed week since I left Monday morning and came back Sunday night. There was only a period of about 4 hours on one day where I could've done anything, but I didn't have access to a PC (it was torture!!). Oh well, maybe next time. It was a really nice week weather-wise. 70-75 during the day and about 60ish at night. A far cry from the 30's in good 'ol Des Moines!

Yeah, I know heat will be an issue, but I'd still rather replace pads than expensive lipos. Besides, running the two speed prevents me from running elec brakes, so the point is moot really...

Hopefully you will get to make it out here again. Maybe RCX? I bet you loved the weather :party:.

Good point about the 2spd vs motor brakes. I just wanted to point out that you might want to increase the number of discs to increase the surface area of heat dissipation.

Would mounting a fan over the brake pads do any good? They may still heat up but would probably be cooled off by the end of the next pass...

BrianG,

I going to let one of my ideas go here. Just give me some time to make something that will make some sense and I'll post pictures. I've been trying to do this for the last 6yrs and never got to it. I was going to patent the idea, but I think it wouldn't be right for other companies to not try it. One company so far has done it, but not in a 4WD 1/8 scale. How good are you in fabricating things?

Depends on how complicated/intricate it is, and what it needs to be made of. Due to the lack of "proper" equipment, I'm pretty much limited to sheet metal bending/cutting, and some fiberglass work.

In my head it doesn't seem complicated at all (My head should be bigger with all the stuff floating around in there), but I don't have any machines to do it and that's when everything gets complicated for me :lol:. Aluminum will work and you should be able to do it. I'll try to take some pictures today.

Lutach, I'm interested to see what you've got there. I'm a very mechanical thinker myself but like you and others I lack the tools necessary to build what I design.

I actually have the tools to make things happen. But, I have alot of projects on my plate right now including patentable items.

If you post pics, I can look at it and see if it is something I can do?

Anyway, I am limited to items that are about 6 by 10 inches in size because my mills are bench top units. But, I have a 4 axis CNC, a 5 axis manual mill, and a small lathe (all bench top units).

I have lots of projects going, but I may be able to do something.

Matt

Here is what I had in mind. AWD braking. I've seen 1/5 and 1/4 scale use this, but mainly in the front wheel and a few do have them in all 4 and my idea will be inboard instead of them being at the wheel. I bought all the parts, but when came time to actually doing it, I was stuck with no time and skills to put it to work. It's easy and if I had the time I could actually do it. I even thought about going 4 discs in the front (Like a dual disc set up for each side) and 2 in the rear. I thought of using a similar set up like found in 1/5 scale, but also do something to utilize linkages to engage the brakes. I have attached a few pictures of the parts and the idea next to a diff case.

One more picture and the idea is out in the open. If someone can actually do this, I'll be happy if you can send me a system as well to put in a HV 1/8 buggy. Keep in mind this idea can be put in basically any scale.

Are you looking for traction control too? You would need a system to compare relative tire speed left to right and compare that to the throttle and steering input. Then all the linkages to control the 4 servos in sync. I can picture exactly what you're going for. Were you going to use the center diff bulk as a front and rear bulk as well? That would make it easier to mount linkages, rather than modifying a normal diff case.

Errr sorry for the semi hijack...

I was going to use the diff case and make holes to a suitable location for the brake pads and I was actually going to have the brakes pads in the front section of the diff, kind of like in a real car. I was going to try and make the preassure on both sides as equal as possible so that vehicle wouldn't push. If it's anything like my racing kart (Wish I could bring it to the US) it should be easy.

Lutach... I have a few spare parts to do this. But I'm like you.... in that I don't know where I'll find the time. I will put it on the list of things to do though.

What I have been planning in a similar vein, is using a single rear brake disc on the rear gearbox, on the input shaft/rear driveshaft. This would give a basic rear brake ability. But your independent brakes would be pretty pimp. :D

The rear brake on the input shaft (front and rear) is nice and I tought of that (So did Ofna :lol: http://www.nitrohouse.com/details_hyper_9.htm), but it should be nice to actually have a system like the real cars.

Cool idea Luciano , I have tossed the concept of a servo/piston hydraulic/calipers system like a real car in miniature but some serious machining there

The trouble with a braking system like this is weight, real-estate, and complexity. Adding a convoluted system would add extra weight, require more room to mount things, and introduce more complexity which would make it easier for things to break. Not to mention that machining things that small will make them more delicate, expecially since they will be taking a fair amount of force. The current method of having the brake on the CD makes linkages easy and relatively compact.

However, this idea would be really neat on something a little larger, like a 1/5 scale vehicle! The reasons I listed wouldn't as big of a deal...

Peter,

I've seen the things you do with aluminum and I know you will make one.

I've seen some really powerful mini or micro servos and I think it would add just a little more weight (Some weight is good for high speed runs), but you will have the stopping power to slow down from 100+mph runs. I will tackle this slowly and will take pictures of my progress. Bare with me when I say slowly I mean slowly :lol:.

I agree a 100% with the complexity end of it
Luciano Once I get caught up on my boats I will get a little more serious with the buggy .....But hey for now

Dreaming is for free

Actually I'm going to start messing with it. I'll do some planning first on where all the components will go and after I sort it out, I'll start marking and fitting before I start drilling away. I know it will be a while before I finish it.

A little more progress:

1) Glued a tapped plastic block to the bottom of the ESC and re-heatshrunk it to allow me to mount it.

http://scriptasylum.com/forumpics/ultra_gtp_5.jpg

2) One of the first things I noticed upon receiving the GTP is the the chassis is quite "flexy", even with the existing front and rear braces. This is presumably from the lack of kickups on the sides. So, I made a top plate out of 6061-T6 Al, and doubles as the ESC mount. VERY sturdy now! I also cut off the excess brake cam shaft so it sits flush with the top plate (gotta make sure nothing rubs on the power wires).

http://scriptasylum.com/forumpics/ultra_gtp_6.jpg

On a side note: I was a little concerned that the HV-110 wouldn't have a high enough current capability for this project, so I looked up the specs for the FDS5672 FETs. Turns out they are rated for 60v, 12A, and 0.01 ohms each (@ 25*C). There are 108 of them on this ESC. And seeing as how there are 36 of them on at any one time (18 on the + coil, 18 on the - coil), that brings the rating to 216A and 0.00055 ohms! Even derating the FETs for 75*C (167*F), they are still good for 130A. And that is continuous current. Peak is much higher depending on how long the burst lasts (ex: if the burst is 0.1s, the rating is 40A each). Seems a tad underrated compared to some of the other ESCs out there.

Looking good Brian! Should be a really sweet conversion. :) Sounds like Castle really did underrate the 110...a lot, lol. I guess they must've known that it's likely to be pushed hard in some crazy setups, so gave it more headroom than some of their other ESCs.

I got some insider info from Castle (they are one of my sponsors) regarding the HV110. Joe and Bernie both told me the HV110 should really be labeled HV140. They have run them in planes at 160 amps for 20 seconds without any problems. Personally, I have run mine on 12S at 127 amps and it barely heated up.

I am a HUGE fan of the HV110.

Matt