Mechanical Brakes
 

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 brushless motor (or brushed) 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.


http://i142.photobucket.com/albums/r...13/problem.jpg
The problem, motor can won't clear the brakes. Pinion does not reach the spur.


http://i142.photobucket.com/albums/r...k413/rough.jpg
Here is the rough motor mount taking shape.

http://i142.photobucket.com/albums/r...3/solution.jpg
The solution is to move the motor back.


http://i142.photobucket.com/albums/r.../clearence.jpg
Mount needs to fit close to the center diff.

http://i142.photobucket.com/albums/r...413/itfits.jpg
With the motor moved back now the pinion reaches the spur.

http://i142.photobucket.com/albums/r...13/brace-1.jpg
Bracket to hold Feigao motor together also strengthens the mount/chassis.

there are much simplier solution prefenting fall feigao to apart
http://www.hot.ee/hblsp/LSP/lsp04.jpg

And your buggy weight will be very high. Try to simplify things. Dp not use thick Aluminium, find solution for lightweight battery holders, and brake servo holder. Save some weight.
I was realy dissapointed first time of weight and handling of my truggy now I reassemble it again but try to save weight much as possible

tom255, thanks for the feedback, I like your motor clamps, were they handmade? And how do you adjust gear mesh? I agree about keeping things light, my buggy is over 9 lbs with a battery. Yeah my mount looks really thick because I wanted a big footprint (mount base to chassis) for strength and I do plan on milling it down and making it lighter. Is that a mini servo on your brake? how is it working out?

Gear mech can be changed like in nitro motor, there are 4 streched holes on chassis, if you look carefully to pic you will see part of hole in chassis on rear clamp. Clamps made by CNC water jet cutter. But those clamps can be made any CNC Milling machine in any metal workshop.
Servo is standart in old design LSP servo posts made by water jet also but in new design i will use only ESC brake look how it work out, if it not satisfy me I will go for Low Profile servo. How i will attach I dont know it yet.
http://www.hot.ee/hblsp/LSP/SSC_0054.JPG
I made battery box from double sided PCB, Cut pieces by CNC router, weld it and reinforced it.
http://www.hot.ee/hblsp/LSP/Bbox1.jpg
http://www.hot.ee/hblsp/LSP/Bbox2.jpg
http://www.hot.ee/hblsp/LSP/Bbox3.jpg
I hope in march I will finish my Truggy

Here is what I did. I think it works good. I would have liked to use the back also.

http://www.rc-monster.com/forum/show...ushless&page=2

Tom255, that is a nice setup, fantastic fabrication work. I don't quite have the machining resources you do so I have to keep things pretty simple. I was thinking of doing the nitro type mount with the slotted holes for adjustment with a Mega Motor but since I have 4 feigao's laying around I decided to use them instead with a regualr endbell mount.

Sparky, that is one nice buggy. Very creative regarding how you handled the braking (ESC and mechanical). Very clean. I think I will go with the dual (front and back) mechanical brakes for now, and if that doesn't work out your ESC/Mechanical brake solution sounds very interesting.

On the battery tray, I am using Maxamp lipos, and they are good packs for the money. But they are a little fragile. The indivdual cells are not bonded together so under hard impacts they can slide around within the shrink wrap which distorts the pack and can rip the tabs off. That is why I don't just strap/velcro them to the chassis, which would be light weight but would not secure them enough for my needs. I have since taken my packs apart and bonded them so they should be more durable, and I may go back to strap/velcro only in the future to loose some weight.

Thanks guys for the great feed back, that's exactly what I was looking for.

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.

http://i142.photobucket.com/albums/r...413/side-2.jpg
Test fitting the servo and linkage

http://i142.photobucket.com/albums/r...k413/top-9.jpg

http://i142.photobucket.com/albums/r.../traybrace.jpg
Additional support post added.

http://i142.photobucket.com/albums/r...bodynobump.jpg
Body before remolding.

http://i142.photobucket.com/albums/r...3/bodybump.jpg
Body after remolding, added a small bump to clear linkage.

Setup my radio brake mixing on channel 3 and it works perfectly. When brake is applied by the radio the mechancial brakes activate, when throttle is applied the brake servo is neutral. ESC brake is set to zero. Can't wait to take it for a test run.

You can also use a Y adapter with your ESC and braking servo to do it too.

Hi offroader, yes I considered a "Y" harness. One issue is when you pull the throttle on your radio the brake servo will move to the on throttle position as well. More wear and tear on the servo. With brake mixing on channel 3 the servo does not move when throttle is applied. Thanks for the comments.

Good thinking I never even thought of that extra wear on servo's I'm guessing it must draw extra power too. Thanks for the heads up.

Interesting mod there shark. I was going to do something similar with my ultra gtp. I would turn the servo 90 deg, so it sat sideways, with the brake cam closest to the center. That way there would be enough room for the pinion, and the body would not have to be altered (in your case, I have a sedan body). This would require making a new top plate, but that would not be too difficult, and it could be one piece.

The concept I envision would be a hybrid setup - mechanical rear brakes only, with a mini or micro servo, mixed into the 3rd channel. You could use a smaller servo by only using the mechanical rear brakes, and you could still effectively adjust front/rear bias completely with your radio. The motor and speed controller would brake the entire diff, and the rear mech. would obviously brake the rear. If you needed more rear bias, you could dial(mix) in more rear brakes on the 3rd channel, or dial out brakes on the 2nd channel(controller brakes).
This setup would save some weight, add some space, allow electronic bias tuning without leaving the driver's stand, and take significant load off the speed controller and motor during braking. I think this would be the best compromise between esc braking and mechanical braking - lighter than pure mechanical brakes and easier to tune, and more tunable than esc braking alone. :)

I got the buggy out to the local track and ran several packs thru the buggy. The mechanical brakes worked perfectly, strong but with great modulation (feel). It made the brushless buggy handle so much better, my poor Kyosho 777 SP2 nitro buggy hardly got any track time. Having run this buggy with motor brake only, for a long time, all I can say is I would never run a 1/8 scale brushless buggy on motor brake again. The difference is unbelievable.

http://i142.photobucket.com/albums/r...413/top-10.jpg

http://i142.photobucket.com/albums/r...413/side-5.jpg

I tend to agree with you on this mechanical brake thing. I made this mechanical brake setup to test the Tekno clutch system on the buggy. I didnt really care for the clutch iitself in the end, but I did really love the mechanical brakes. The mini servo has plenty of power to lock up the tires on any surface I've tested so far and it has much more feel and adjustability than any of the motor brake setups I have had.

I just preordered the new Xray XB808 buggy and plan to convert it right out of the box. This brake setup is going on the new buggy, but I am going to flip the dif back around and use a standard pinion setup rather than the clutch.

It for sure adds weight, but I do much prefer the feel, and the mini servo doesnt add that much weight and gets its power from playing with leverage on the arm.

http://i66.photobucket.com/albums/h2...z/e302271b.jpg

http://i66.photobucket.com/albums/h2...z/b68edc38.jpg

Ignore the Rx pack. I put it on there temporarily while I was waiting for a UBEC to come in.

jhautz, that is one clean setup. I really like the innovative linkage you got there to run the mini servo inboard. Nice fabrication too. Yeah I was wondering what that extra battery was before I read your caption.

Hey, jhautz, what kind of buggy is that in the pictures? Just wondering, thinking about doing a brushless buggy, haven't decided which one to get though.

Thanks shark.


Fast5 - Its an Xray XB8EC. You can grab lightly used ones for some great deals right now on Ebay. They arent even a year old cuz the EC was just released last April. Xray is releasing a new buggy in a few weeks and there are lots of folks dumping the ECs and TQs for good prices so they can get the new one. I think they are awesome buggies, infinaltly adjustable and tough as nails.

looks great guys


jhautz....which servo are you using?

my old stadiumm pro had mechanical brakes. saddle packs make it easy.

Hitec HS5245MG
Torque:61.10 / 76.37 oz.in (4.8v/6v)
Speed: .015 / 0.12 sec @ 60 deg.
Size:1.27" x 0.66" x 1.21"

:yipi:got mine done on my xt8 , but my wife took the kids out of town and has the camera with her so it will be a few days for pics:oops:, i used a full sized servo with the frt. and rear brakes, servo fit inbetween the steering servo and pinion, mixed 3rd channel

had to gear 18/48 to use the rear brakes, off to check the speed calc.:whistle:

xt8 with mechanical brakes
 

heres some pics, its very solid and works great, took it for a drive today, just dont forget the locktight on the rear screws:lol:


my only concearn with this is after 10 minutes of speed runs my temps were 160* motor, and 135* on the esc. w/o fan,(40* outside), but i cant change my gearing , i dont think that a 17 tooth pinion (1 less then now) would work, there is like 1-2mm between the motor can and the rear brake pads

any thoughts or comments would be great

punch cont. was @ 80%
motor timing normal
motor start power low

**minor cogging on start-up ..... is this caused by the start power or the punch control or timing??
this is not a hyjack, i just thought it would be a great place to discuss these set-ups


http://i170.photobucket.com/albums/u...s/IMG_1510.jpg
http://i170.photobucket.com/albums/u...s/IMG_1511.jpg
http://i170.photobucket.com/albums/u...s/IMG_1508.jpg
http://i170.photobucket.com/albums/u...s/IMG_1507.jpg

Nice build entjoles

I found the same problem with the gearing when using brake disks. You can only get the motor so close before it rubs the disk. With a standard 36mm can like a Feigao XL or Lehner I can get a 16/46 to work (but its VERY close). The only solution I found was to run a low KV motor and then use the taller gearing to get the speed. If your using a 9xl you may need to go to a 10 or 11 xl to get the right speeds with the gearing that will fit for you.

Another thought that I had, but hadn't tried it yet was to get a couple of Mikes motor front plates he makes for the Lehners and Neus and stack them up so it pushes the motor back from the actual motor mount and then you could cut a flat off on the side of the adapter plates to let the disk go in and the disk would actually kinda be between the motor and the motor mouunt plate. That woul let yu get the mtoor in closer with the brake disk.

the speed calc. says around 40 mph on 4s which is what i run my 9xl on, i will just run it till i thermal or ruin the motor

thanks for the suggestions, do you think that i should consider a 1700kv motor and keep the gearing the same? would the temps be ok?

so a 1515 2.5d /s would be a good option? the speed calc. says it would be 39mph


i think it felt much better with this braking and i was only running on asphalt

Yea kv wise the 1515/2.5d would be good, but its a bigger diameter so it forces you to use a bigger spur. I would look at going for a 36mm can motor. Feigao, Hacker, Lehner, etc....

are the 1512 series the same diameter?

the 3d/s would be an option if it has a smaller diameter, but for some reason i think the neus are the same diameter but are diff. lengths

Yea. All the Neu 15xx motors are the same diameter. The finned cans are even bigger.

I think the Neu smooth cans are about 40mm. That 2 teeth on your pinion you would be giving up with the extra 4mm motor diameter vs a 36mm can motor.

Regarding the pinion clearence, one of the biggest issues using mechanical brakes is that because of the motor can hitting the disc there is a limit on how small you can go on the pinion. I solved this by spacing the motor back a few milimeters so that it clears the disc and therefore I can run very small pinions (10, 11, 12, 13T). Since I am running the Kyosho 46T spur and a hot running Feigao I need to run a 12 or 13T pinion. This also eliminates clogging. On the downside, this setup puts the pinion on the very end of the motor shaft. Because of this I built up the motor mount/chassis to be extra stiff (no flex). So far I have had zero issues with this setup.

http://i142.photobucket.com/albums/r...3/P1010021.jpg
This is a 13T pinion.

http://i142.photobucket.com/albums/r...P1010020-1.jpg
These pictures show the test fitting and the rough parts (motor mount).

Looks good shark. That is the solution I was trying to describe a couple posts ago.

Last night I sketched up a spacer plate for the front of a motor that would allow for the brake disk clearance and just sent it to Mike to see if he could machine one up for me. It should allow the use of an almost full range of pinion gears. At least down to 12T by my calculations. It should be able to bolt up to just about any motor using a normal bolt pattern and with any of the RCM style motor moounts allow clearance for brake disks. Like you said though shark, it will put the pinion farther out on the shaft, but I have been running a really long Tekno clutch assembly in one of my buggies which effectivly almost doubles the shaft length where the pinion gear is and havent had any issues so I would think this should be fine too.

Heres the sketch of what I'm thinking.

that looks like a good idea, id like one as well if he makes some ,lmk , if not i could use some aluminum and make a spacer to allow me to gear back to a 16 tooth pinion or smaller , which gives me better motor temps


thanks

heres one more pic to show the clearence

http://i170.photobucket.com/albums/u...s/IMG_1519.jpg

ill have to get a measurement on the thickness of the adapter, to clear the brake pad bolts, and then use a long shaft pinion

I got a response from Mike today. He said he would try and make a couple of the spacers I posted sometime this week. It should be pretty easy for him to do with just a couple tweeks to his program for the front motor cover.

I'll post up some pictures when I get it and install it.

sounds great, if it would fit the motor i have id take one as well, but i dont plan on running this motor forever:wink:, just need some $$$$$$$$

It should fit any motor that has a standard bolt pattern. If its the 9xl you are running it will fit.

Just send Mike a note and tell him you want one of the motor spacers he is making for Jeff. I'm sure its no sweat to make another one once he is set up and machining them.

ok i just sent mike an email....

i mocked up to check .... and it should work sweet, i used spacers i had and i think its about 4mm thick so that is right, and i will have to dremal a very little on the outside brake pad (1mm) and will also trim a small amount off the heatsink/motor clamp to ensure the brake disk wont hit .. heres some pics from my mockup, oh and i have plenty of shaft for pinion mounting, i used a 15 tooth in mockup but i should be able to use less as well


http://i170.photobucket.com/albums/u...s/IMG_1527.jpg
http://i170.photobucket.com/albums/u...s/IMG_1525.jpg
http://i170.photobucket.com/albums/u...s/IMG_1523.jpg

Could Mike possibly add the 4mm to the front of the heatsink/motor clamp during machining? That would take care of two problems at the same time, and you could free up a mm or so by combining the two. That would maximize the motor shaft available length. Just a thought...

Yea linc. That would work for sure, but I dont think Mike makes those motor heat sinks in house any more and changing a big part like that is sure to be alot harder to do than just making the simple adapter plate, but its definitly worth asking him about if you want it.

I personally am not planning to use a motor that requires an clamp/heatsink so it woulnt work for me.

Entjoles, The plate I asked him to make for me was thicker than 4mm. I think I will need 6.35mm (1/4") to clear the whole brake mechanism. Thats what I asked him to make for me.

ok thanks, ill shot him another email

i also trimmed off part of the hs/clamp and got lots of room:yipi:

it will accept a 14 that i have and maybe a 13 if i dremal the brake pad plate

so i could just use a neu adapter plate with part of it cut off right?

this is the size i will need when i get a diff. motor w/o the heatsink clamp

my 4mm + the hs.clamp of 2mm = pretty close to what you came up with

i wish i had a caliper:lol: