Doing a Brushless Conversion. Advice Please.
 

Hi, I am going to start my brushless conversion next week. I am starting with my existing Savage, and outfitting it.

The truck I am starting with: savage ss 4.6 with FLM extended LCG TVP's. Big joe wheels + tires. Alum corners, but plastic arms. Alum bulkhead. X SS diffs (4-spider, allow case). JR 400oz/in steering servo.

SO far, this is what I have done:
Removed all nitro related components, ditched the 3speed, and removed throttle servo.
I have a Kershaw direct drive and MMM 2200kv combo on order. (both should arrive some time next week)
I had dan customize my gearbox so that the motor will mount in the front. This will leave enough room in the rear for batteries (~5.75" length battery MAX). I did this so that the batt's would be safe inside the TVP's and not be affected by collisions and such.

All I have left to get is the batteries. I am not sure whether I should go with 6s, 5s, or 4s battery. The kershaw gearbox has a lower internal ratio than the stock transmission (3rd gear), and I am running with 13t pinion and 52t spur.
Any input would be greatly appreciated.


Thank you in advance,
Sutyen

Pair of 3s lipos and gear down a touch sounds like the best plan for a large truck like this- you wont fit a single large 6s lipo.

I used the rc calculator. I set it up with stock hpi stuff, and then changed the internal ratio to 2.5 (kershaw has 45t and 18t in the gearbox, 45/18=2.5). It said with my 13t pinion I would get to 36mph (big joe tires). You still think I should gear down?

Also, I already knew I was going to work in pairs regardless, I have 2 3s chargers (an mrc 977), so i can't charge a 6s anyways.

I also just realized I will also need to order some balancers. Do you have any suggestion for balancers compatible with the mrc 977?

I would gear up, my Neu 1515 1y (2200kv) motor pulls my XL around (losi 420 tires) around with no problem geared for 48 mph on 4s (16 tooth pinion, stock 3 speed) I was going to run 26 tooth pinion on my direct drive to get back to normal speed. My DD should be early this week.

I like my blinky balancer. Just plug it in and your good. No need for different wires and adapters. It doesn't balance that fast, but its never needed longer than the charging time. Its also small.

And I would keep the gearing at around 35. If everythings running nice and cool you could gear up afterwards.

So, basically, i thikn I am going to stick with the 13t for now, and gear up later if I deem it necceasry. I will be monitoring the temps closely with my nomadio controller's telemetry. I will keep one temp sensor on the motor, and one on the batts. I believe the ESC has built in temp protection, so I am not going to worry abuot it.

Has anyone has experience with zippy flightmax 5000mah 25c or 30c batteries. THe 30c is slightly shorter, so are preferrable to me, but hobby city is currently out of stock. The 25c is still in stock, but I want to ensure that they are adequate. Do any of you have experiece with these packs?

The other option are the SPC 15c 5000mah batteries. People say they are more like 20c, but I think the zippy packs are better. If you guys think that the SPC's are, in fact, better than the zippy's I am willing to spend the extra money.

enerland batts are the ones.

ok... they are also a lot more expensive. I am willing to spend more moeny, but only if the cheaper batteries are not adequate for my setup. If the zippy 25c are good enough, I will order them. If they are not, I will start looking elsewhere.

Another question. I know that braidign the wires reduces noise, but how tight should you make the braid, and does it damage the wires?

It wont damage the wires so long as it isnt too tight...

hard to desribe- just make sure you arent tugging at the wires where they meet the esc & motor, you need a certain amount of flex/movement.

Ok, I got my gearbox, and there were some hickups with assembly, but I have sorted most of them out now.

Here are some pics of it: http://picasaweb.google.com/sutyen/B...eat=directlink


So, there is not enough room for the stock plastic spur gear, so I was wondering how much thinner the steel spur is compared to the plastic one. If it is about 1/8th thinner, i am for sure fine, and 1/16th thinner I might be ok.

Also, what gearing do you all reccomend. THe gearbox has internal gearing of about 2.5:1 I would like to use a 47t spur if possible, as that will fit the best, and have the least interference with the chassis. HOwever, becasue of the gearbox design, the smallest pinon available with that spur is 15t. I can go bigger than 15t, but not smaller. 47:15 a good spur:pinion ratio for this gearbox/motor? (2200kv mamba monster combo)

Thanks for any help in advance.

http://www.scriptasylum.com/rc_speed/_top_speed.html

Easy to use, just enter your info and adjust the pinion/spur until you hit about 40mph or so.

oh sweet, 47/15 gives me exactly 40.6mph

Ok, so I finally finished building my truck, I plugged in my lipos (not fully charged, the cells are at 3.7v each, so at storage charge, not dead either) The first thing I noticed was a large spark as I plugged in the batts. The car still ran, but I am not sure that it is normal. I am using deans ultra connectors, and have the batteries wired in series via a "Y" shaped adaptor I made using 3 deans and 3 wires. (mamba + to battery 1 +, batt 1 - to batt 2 +, batt 2 - to mamba -) All works well when plugged in, as I can drive the car (only went in a small circle in my room to make sure everything works). THe spark was pretty big though, and it kinda scared me, so I wanted to make sure that the spark is normal. Is there something I can do to prevent it?

Also, i noticed that running the vehicle produced a very high pitched noise under acceleration. Also wanted to verify that this is normal.

Lastly, I have a question about mounting lipo's. Is it better to keep them snug and surrounded by only aluminum, or is it better to leave some space around it with foam. I currently have the lipos surrounded with aluminum, with foam in front and behind. The sides are directly up against aluminum. I thought this would help with cooling. I don't know if its the "safe" thing to do with lipos, as I have never used them before, and for me, as a weekend basher, safety comes first

To define snug for those bateries, this is how I have it set up. I have one L bracket on the left side of the batteries. With this in place, there is a little bit of movement with the batts. I then put a 1/32" alum sheet metal on the right side of the batts, which is a slight squeeze to get in. Basically, there is no movement side to side. There is another wall I put in front of the batts, which leaves about an 1/8" of space. I filled this by squeezing a bunch of foam in fornt and behind the batteries. I also bent the 1/32" sheet (to the right of the batts) so that it would also cover the top of the batts. I put a thick piece of foam above the batts, and below this sheet. When I tighten down the velcro straps, the foam is reduced to 1/8" thick, and the batts pretty much don't move in any direction. I will posts pics later, I don't have my camera with me right now.

My basic question is: Should I increase the space to the left of the batts and stuff some foam in there? Or should I leave it as is, which will allow the slum to keep the batts cool.

The spark is completely normal when connecting the plugs, it's something to do with the plugs charging up. The bigger the batterys the bigger the spark. It's nothing to worry about, it does wear the plugs a bit but thats all. There is a way to prevent the spark, but it is forbidden to mm/mmm controllers.

This might be the slipper. You should look that the slipper is tight enough, that it won't slip too much under the acceleration. Not too tight either, so your drivetrain will last longer :tongue:

First, A spark is normal when you plug your batts. in. Remember, you are using quite a bit of juice to power your truck! The high pitched noise is also normal...just make sure your gear mesh is correct. I would cushion the sides of the batts as well. Keep them as tight as possible w/as little movement as possible. Remember, you want some air to go over, around your batts. for cooling purposes. With that being said, you also want the batts. as snug as possible to keep the cells from shifting around.

I look forward to seeing some pics. and I hope that this helps!

Thanks to both of you. I think I will start by tightening the spur, I left it pretty loose because I don't want my diffs to blow up, lol. I will compensate by increasing punch control. I am gonna start at 70% and slowly decrease it until I am happy with performance.

About the batteries being snug with cushioning AND having air around them. THis might sound liek a stupid question, but can't the velcro straps damage the batteries if they are directly against the batts, and you land upside down (all the inertia of the batts pushes them against just 2 thin spots). That is why I kept all sides with plates, to spread the load of any impact. I am thinking maybe I should put cushioning on one side of the batts, but still keep the other side direct to the alum, as a heatsink. Does this sound like the right thing to do? If I put cushioning on both sides, should I remove the top plate, and just run with the velcro on top?

http://lh5.ggpht.com/_VtI5ncEaJBM/SZ...2/100_0142.JPG


http://lh4.ggpht.com/_VtI5ncEaJBM/SZ...2/100_0143.JPG


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http://lh6.ggpht.com/_VtI5ncEaJBM/SZ...2/100_0155.JPG

The pics aren't very good, but I'm not a photographer, and my room is a mess, lol. I'll try to get better pics later. Only thing left is the roll cage. Haven't ordered it yet, but it's gonna be that nylon cage (imun80 or whatver its called). Need some funds before getting the rollcage. I ran it a little earlier with 6s lipo, 50% punch control medium power delivery (a setting for mamba monster), and a loose slipper (it slipped a LOT). I want my weak diffs to last a while, at least until I can afford the roll cage and CEN diffs. It was still popping some wheelies though. I think I can afford to tighten the slipper still, cuz the front didn't lift more than a few inches off the ground. Is it bad for the slipper to slip too much?

Had to make a custom skid plate to accomodate the kershaw gearbox which stocks out a tad from the bottom. Made the skid plate start at the rear bumper (giving a solid mount for a wheelie bar if I choose to get one) and basically extends the existing plastic skid in the rear up to the front, then bends down right in front of the gearbox, and attaches to the stock front skid mount. Note that the stock plastic skid in the rear is still there, but under the new skid.

For full size images, go here: Brushless Build

loose slipper will eventually ruin the spur gear & the diffs are strong enough to handle a nitro beating them so tighten up the slipper..Also the high pitched noise could be from the motor not the slipper

Def don't run the slipper too loose. It will heat up and ruin the pads quite quickly, and motors can also run hot too if driving a loose slipper. Its best to learn throttle control or lose some cells in the batts until you are comfortable with it. Maybe turn down the thr EPA, tho I'm not 100% that the esc will like that.

The diffs should be ok provided you treat them nicely. Don't launch the truck really hard, and don't slam on brakes at high speeds.

As far as lipos, I've never had a prob strapping them down. Def put foam around them. If they need "cooling" and heatsinks, you have too small of batteries. They shouldn't get warm at all.