Shark413

I've had my brushless Kyosho buggy for almost a year now and I have been very pleased with it. It handles well, is blazing fast, pretty reliable and just plain fun. It is surprisingly competitive with nitro buggies with one exception, the braking. Don't get me wrong the motor brake is strong and can be finetuned via the MM ESC, but in my opinion it still lacks the same feeling you get from a good mechanical brake setup. My biggest issue is that you cannot adjust brake bias using a motor only brake. So, I decided to mod my exisiting motor brake only buggy and add mechanical brakes. I search this forum (and others) for info and came up with design below. The issue is when using a standard brushless motor (or brushed) mount to power a nitro center diff equipped buggy the motor will not clear the rear disc brake or will not allow a small enough pinion to be used. Nitro cars have a long crank and a clutch bell that allows the engine to clear the brake. To get around this with a brushless setup I decided I needed to move the motor back about 6mm to get the necessary clearence. I made a new motor mount from scratch that attached to the chassis and placed the motor back enough to clear the brakes. The mount was made in such a way to fit very close to the center diff mount which allowed the use of smaller pinions. Since the motor mount was now no longer part of the center diff mount I was concerned with chassis flex causing gear mesh issues. But after looking at my overall design, the aluminum battery tray and special motor bracket (used to hold the Feigao endbells on) seemed to really keep the flexing under control. This buggy is still a work in progress, I still need to mount everything, construct a bracket for the brake servo, hook-up the linkage, setup my ESC and radio mixing, etc. I wanted to share my project with all of you and perhaps get some constructive feedback. Sorry for the long post.



The problem, motor can won't clear the brakes. Pinion does not reach the spur.



Here is the rough motor mount taking shape.


The solution is to move the motor back.



Mount needs to fit close to the center diff.


With the motor moved back now the pinion reaches the spur.


Bracket to hold Feigao motor together also strengthens the mount/chassis.

HandyRacing

Very cool. We havent tried to keep the mechanical brakes, just using the motor brake like others we know in our local track crowd. As we never ran a Nitro before (we got a roller and went straight to brushless), we didnt have some of the before after experience.

(One test drive of a Nitro in the Fall is our only Nitro powered experience)

SO we're still learning.

One thing we did run into was with a Kyosho 46 tooth plastic spur, when we dropped to an 11 tooth (Mod1) pinion, our motor mount setup left us crowded to the center brace and it did cause us gear mesh issues. When we moved back to a 12 tooth pinion we had clearance for proper mounting. We don't have the finned Fiegao motor, but we are using the bolt on supportive bracket with heat fins from RC-monster.com.

(Jammin X1CR)

Long posts are better, great job. Thanks.

hrdcoreglf

With what servo are you going to actuate the mechanical breaks?

Shark413

Hey guys thanks for the comments.

HandyRacing, I really miss brake bias, unless you have driven a center diff two brake buggy it is hard to explain. But brake bias has a huge impact on how the buggy handles.

hrdcoreglf, regarding the servo I am not sure if I will go standard or try a mini servo. I would like to go mini because it will save space and be lighter, I am just concerned if it will have enough power to give me the brake feel I like.

FoamyVictim

85 OZs of torque is more than enough. I wouldn't use less than 65 or so... A standard servo with 50 did OK, but not well enough for me. I've been running a Z590 for over a year now. It uses less power than a digi, or a super high torque unit, and handles the job with ease. Are you planning a brake for the front as well, or did you plan to just dial it in with the electric motor? That might be better, since the bulk of the braking on a tight track is with the rear. Then the bias could be adjusted with the servo, and let the ESC do the rest.

Shark413

I plan on using both front and back mechanical brakes. One of the main reasons I am going thru all this trouble is because with motor only braking when used with a center diff, when you apply the motor brake the center diff wants to do it's thing (send braking power to the side that has less traction). This can lead to inconsistant braking depending on the diff action (oil weight, traction available at the time, etc.). You can tune braking action via the diff using different oils but then you also impact the diff action when on power. You can control motor braking action via the radio and ESC, but you still have a center diff that can vary the amount of braking power to the front/rear wheels. I like the idea of the braking action being completely separate from the power on action. I really like the way my nitro buggy feels (brake action) and I want to try it in my brushless buggy. It's alot of effort, but if it does not work out I can go back to the motor only brake.

HandyRacing

So you're intending the trigger moved forward will activate the mechanical brakes via servo(s) and, thus brakes will also be programmed out of the ESC / motor (programming easiest done with a Mamba Max or future Monster Max ESC)?

This removal of braking from the electric motor will leave the motor is a bit of a coast, not unlike a Nitro with a clutch would also respond?

Seems not so complicated in set up, only physical arrangement of hardware.

FoamyVictim

Well, there's one more variable in this equation. If the motor remains connected to the spur, then it will produce drag when you let off the throttle. Only with a nitro motor's clutch is the drag almost completely gone when the clutch disengages. I wonder how this will affect performance. I commend you on your efforts, and hope you can make it work. So far, that would be the best conversion to date.

The Hedgehog

You have to remember that brushless motors have hardly any drag at all. Hence why people program drag brake in, because they are used to the standards brushed motor's resistance. It does vary motor to motor, and you are right it will be interesting to see if this has an effect.

FoamyVictim

Yup, I was thinking for sure there'd be more mass than a clutch bell. But until he gets it assembled and on the track, we can't be sure of anything. Of all the brushless conversions for 8th scales that I've seen, this one has the most potential for racing applications.

Shark413

Hey guys great coments.

HandyRacing, yes the plan is that when you press forward on the trigger you will activate the mechanical brakes just like on a nitro buggy. The ESC brake will be set to zero, so the motor will freewheel.

Autoxman, correct, brushless motors have little or no drag when in neutral.

I have finished with the motor mount and brace and am looking at how to hook up the brake servo. I looked at mini and micro servos but I want to use a standard size servo, first because I have several spares, second because they are high torque models that will supply good clamping force. I am having more trouble trying to figure out how to mount the brake servo than I did with the motor mount. It will have to sit a little more outboard than the nitro version to clear the pinion, but that should be ok. The standard nitro radio tray (with steering/brake mounts) is about 10mm too long and won't clear the motor mount. I will either have to fab one from scratch or hack up the stock tray. I am also replacing the center diff (it is a TCD or limited slip model) to a more standard open diff. I originally had the TCD installed because I thought it would improve the motor braking feel, but it really didn't improve brake feel and it made the buggy looser under power which is not what I was looking for.

Jerzferno

Nice job in the machining department.

kvrc

shark413 good job on the project.

for all the nitro guys that may be hesitant about trying to convert a buggy because of the lack of brake bias dont be. i have let hardcore nitro guys run my buggy as well as many of my friends conversions. yes it has a different feel but they all adapt quickly and find it not to be a problem. when you think about it, from what i have heard most guys set up more rear brake. when you hit the brakes on an electric conversion the froward transfering weight basicly sends most of the braking to the rear.
most of the guys i know run 1/8 electric buggies on tight 1/10 type tracks where proper braking is the most needed.
many of these guys also run 1/10 4wd cars and they are able to get their 1/8ths around the track just as fast or faster.

HandyRacing

Come watch this weekend, as the 1/8 scale buggies and truggies run at the Washtenaw indoor track.

Times from this winter's racing and link to the track info are posted here: www.rcproductdesigns.com

kvrc

i wont be there this saturday but i will be at the last fun day race with my E raze. dan knows me very well so he can point you in my direction. i hope to see you if you will be there that day.

sloppyG

you could look at the tekno clutch kit, that allows the motor to be placed a bit farther back

they have a small diameter flywheel that will work on 1/8 buggies, probably cost you about 50 for the tekno stuff and the clutch parts if you tried that route

HandyRacing

[/quote]
i wont be there this saturday but i will be at the last fun day race with my E raze. dan knows me very well so he can point you in my direction. i hope to see you if you will be there that day.
[/quote]

I wondered given the local address, watch for my pit towel with the Handy Racing sign. Look forward to meeting you.

Shark413

sloppyG, I looked at the Tekno clutch. It is a very interesting idea, and for reducing drivetrain strain (similar to a slipper clutch) it sounds like a good idea. It also probably makes the car feel more nitro like as well, because of the slippage. But for me I like the instant on power that a large brushless motor produces. A perfect example is at the local track there is a big turn followed by a triple jump. With a nito buggy you have to drift wide and then peg it to get enough speed to clear all three jumps, a much longer route. With my brushless buggy I can cut the corner tight and then hit the throttle and it easily clears the triple, which is a much fast line. But like I said, I miss the feel of mechanical brakes and the ability to adjust bias. The motor only brake just feels to vague for my taste and is inconsistant. And one last thing, generally a brushless conversion is heavier than a nitro buggy of the same make, because of the extra weight of the battery. So you need that extra punch that a clutch would take away to make up for the extra mass of a brushless conversion.

Shark413

I had some free time last night so I was able to work on the buggy. I was able to mod a stock aluminum radio tray to fit over the carbon fiber tray. I added another tray post to support the end of the tray. This holds the brake servo, which I test fitted and everything looks good. One issue, since the brake servo is a little more outboard than normal the linkage hit the body slightly, I remolded the body to create a small bubble to allow clearence for the linkage. I am waiting for longer linkage rods to actually hook up the brakes. Then I will setup the ESC for zero brake, use channel 3 brake mixing to control the mechanical brakes and hopefully be able to test it at the track next weekend.


Test fitting the servo and linkage




Additional support post added.


Body before remolding.


Body after remolding, added a small bump to clear linkage.

HandyRacing

I suppose body "remolding" might be a separate thread opportunity and perhaps in many situations not even limited to a conversion, but it seems this is a common issue with doing these conversions (we also have issues with limited space vs desirable location in our 1/10 scale buggy for normal operations). We ran into the issue of "wanting to place something" namly the ESC and cooling fans in a certain location but were limited due to body clearance.

(Last night) as we were trying to re-arrange our cooling fan set up, I began to wonder if a partial mold could be made up or scrounged and then by simply (and gently) using a heat gun could we change the body to better suit our needs?

Can you give a short descrition of how you did it? Thanks.

FoamyVictim

Is there a reason you couldn't move the battery further back, and put the brake servo here? Seems like it wouldn't stick out as much...(forgive my crude graphic, just thought it would help me explain)

Shark413

FoamyVictim, To get enough power to move the 9 pound buggy I have to use a 4s2p lipo. This pack is very large and basically takes up the entire side of the chassis. Check out the pictures and you will see there really isn't any room to mount the brake servo on that side. Space is very tight and I had to be very creative finding space to mount the ESC, power cap, battery and BEC.


Bare battery tray.




Older picture showing the 4s2p battery mounted in the battery tray.

FoamyVictim

What kind of run time do you get out of that large battery? I believe I could do fine with about 15 minute of runtime. Do you thin it would be possible to run a lower capacity battery? I fly airplanes with Li-po packs, and there are a multitude of sizes available. I was thinking about 3500 mah, and 3 cells. I don't think I'd need a 4s pack, or any where near 5000 mah....

Shark413

FoamyVictim, I get about 12 mins of full power out of that battery/motor combo. You can use a smaller (mah) lighter battery but what you have to remember is the larger mah batteies normally provide more juice (amps) for the motor. I would not run less than a 6000mah battery on this size buggy with a Feigao XL motor. I have tried 4000 and 8000mah batteries and the 4000mah was lighter but lacked punch and the 8000mah felt like the 6000mah power wise but was just to heavy for a buggy. And the 4000, 6000 and 8000 are batteries are basically the same size, length and width wise, with just the heigth being different. So for me the 6000mah battery is a good compromise between weight and power.

FoamyVictim

So, do you think a 3S pack would come close to a nitro in performance? I'm not looking to go faster, or have better acceleration than nitro, I'd rather try to match it. I'm actually pretty surprised that none of the companies that make 8th scale buggies have come out with a purpose built version. I imagine some things could be changed on the chassis layout to suit an electric drive system...as long as they keep the mechanical braking system...