Doing a Brushless Conversion. Advice Please. - RC-Monster Forums

spiftacu1ar · **Doing a Brushless Conversion. Advice Please. -** 02.01.2009, 04:53 AM

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

suicideneil · 02.01.2009, 05:28 PM

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.

spiftacu1ar · 02.01.2009, 05:33 PM

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?

doo540 · 02.01.2009, 06:00 PM

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.

02.01.2009, 06:02 PM

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.

spiftacu1ar · 02.01.2009, 07:01 PM

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.

Gdot · 02.01.2009, 09:07 PM

enerland batts are the ones.

spiftacu1ar · 02.01.2009, 09:31 PM

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.

spiftacu1ar · 02.03.2009, 01:42 PM

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

suicideneil · 02.04.2009, 06:26 PM

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.

spiftacu1ar · 02.10.2009, 01:26 AM

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.

suicideneil · 02.10.2009, 01:45 PM

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.

spiftacu1ar · 02.10.2009, 02:14 PM

oh sweet, 47/15 gives me exactly 40.6mph

spiftacu1ar · 02.15.2009, 04:18 AM

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.

Hardstyle · 02.15.2009, 09:45 AM

Quote:

Originally Posted by spiftacu1ar

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?

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.

Quote:

Originally Posted by spiftacu1ar

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

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