My brushless Revo

[Finnster]

Thought I'd start a thread on my BL Revo. I based it on Dafni's and Brian's and a few other's I've seen, with a few tweaks of my own. I decided to use an Emaxx tranny (sold the rest to fund this, should cover it entirely!) locked in 2nd gear. I removed the 1st gear idler and metal input gear to remove as much rotational mass as possible. The 2nd output gear is bolted to the dog gear w/ 12.9 screws. Should be very strong, but reversable in case I blow up a bearing (vs epoxy.) I am happy to report the tranny weight w/ steel idler was ~220g, about the same as a stock Revo tranny (~220g.)

the Batt trays are made from UMWPE, nearly indestructable with the weight close to CF (1.71 g/ml vs 1.61 g/ml CF.) 6061 alu is listed as ~4.1 g/ml. They are made form 2" angle, 1/4" thick. Works very well as was very easy to mold and cut, as easy as wood. Total weight was ~100g.

I was able to flush mount all the screws and bolts onto the existing chassis mounts. The bottom side is very smooth, and the whole mount very strong. I may trim alot of material out when I get a chance, but they are light enough now they are not a high priority now. Hopefully I can dye these later.





I just need to finish the front drive shaft install, the mount for the Rx and the Esc and its pretty much done. I may or may not put all 8 screws in the tranny The middle 4 don't seem to be critical, and I wonder if they are there more for the Maxx chassis the way it ties the chassis to lower braces. I will eventually going to 1 steering servo, but its good enough for now. Overall the conversion was very easy. The hardest part was the batt trays, but even then it was easy.

I will be be running an 8xl with 14 and 16 cells. I have a strobe and will be getting the 51t spur. Does anyone have any recommendations on a pinion? They are $12 ea so I don't want to do a lot of experimenting. LMK what you think and thanks to those who have already helped me get this far! I will eventually radar this to get some solid Bl #'s.

[crazyjr]

you may need some protection on the inside of the battries, because it looks like it might short if knocked the right way

[BrianG]

Nice motor and dogbones. ;)

Have you tried to fit a body on there yet? It looks a little on the wide side. That's actually why I'm limited on battery size on my V2 Revo. And as crazyjr says; either protect the inside of those batts or just use some velcro strips and wrap them across and around the batteries/holders. Interesting choice of material - nice, lightweight, and sturdy. It looks like the type of material used in some cutting boards. Where do you get that stuff?

[Finnster]

Originally Posted by crazyjr

you may need some protection on the inside of the battries, because it looks like it might short if knocked the right way

It doesn't look like it, but the batts fit in there very tight with the straps and up against the servos. I do have some other straps, not pictured, that wrap around the whole batt tray width wise.

[Finnster]

Originally Posted by BrianG

Nice motor and dogbones. ;)

Have you tried to fit a body on there yet? It looks a little on the wide side. That's actually why I'm limited on battery size on my V2 Revo. And as crazyjr says; either protect the inside of those batts or just use some velcro strips and wrap them across and around the batteries/holders. Interesting choice of material - nice, lightweight, and sturdy. It looks like the type of material used in some cutting boards. Where do you get that stuff?

Yes, they are very nice. :)

The one side fits the body perfect, the other side pooches out just a bit next to the steering servo. I really don't mind it, but some sticklers may. :P

I got the materials from McMaster-Carr, possibly the coolest website I've ever played with.:) They seem to have everything, including all sorts of very nifty stuff and easy to find. Metals, plastics, screws, etc etc. Cheap fast shipping too. Overnight was $4. The 2ft angle was only $5.

It may be the stuff they make cutting boards of as well. Its stiff and strong and insulating. As mentioned, I got velcro straps from them as well to wrap around the batts for overkill. You may be able to see there is some room to wrap a strap between the chassis and the trays. I like the width tho. Low CG w/o losing clearance. Once I get the gears, I'll be able to take it out for a spin.

What gearing did you use? 14/51? How did you like that, or do yuou think it could go up a bit? Sounds like yours ran really cool.

[BrianG]

I might check that site out. I'm always looking for good places to get raw materials. OnlineMetals.com is good for metals, but I'm always looking for plastics and the like. Local retailers are worthless for this - at least around here.

14/51 worked well for me (you should've mentioned you wanted a 14T pinion). However, since yours may be lighter, you may want to go to 15T, but I'd get it all together and try it out first. Mine wouldn't wheelie because of the weight distribution, but all four tires would spin easily. I don't think you'll be disappointed in the power. What ESC do you plan to use?

[squeeforever]

Originally Posted by crazyjr

you may need some protection on the inside of the battries, because it looks like it might short if knocked the right way

I don't think you need to worry about that because it appears you have heatshrink on your batteries.

[Finnster]

Originally Posted by BrianG

I might check that site out. I'm always looking for good places to get raw materials. OnlineMetals.com is good for metals, but I'm always looking for plastics and the like. Local retailers are worthless for this - at least around here.

14/51 worked well for me (you should've mentioned you wanted a 14T pinion). However, since yours may be lighter, you may want to go to 15T, but I'd get it all together and try it out first. Mine wouldn't wheelie because of the weight distribution, but all four tires would spin easily. I don't think you'll be disappointed in the power. What ESC do you plan to use?

I've checked out OM.com, they seem pretty good too, just a narrow selection of raw materials (metals only.) I'm leaning towards a 15t, but it always takes a bit of experimenting for me to get it where I want. Just a bit pricey at $12 ea. I'm looking to get a good balance of speed, TQ and runtime (aren't we all?) If it doesn't wheelie its ok, I have the Rusty for that :) Gets to be a bit of a trouble at times.

At your suggestion, I went to Ratshack and got a cheap cap for the 9920. Put it in the Rusty, worked great, but just not as smooth as the Mtroniks I have. Allelectronics.com has better caps which I may pick up when I order some fans. I can't find any "fast-switching" caps in that spec tho, so I don't know what diff this will make long term. I'd like something like the Q125, just don't want to spend another $280 when that's about what I've spend on the whole truck so far. :( We'll see.

[BrianG]

Yeah, radioshack isn't known for their quality parts. You could also try smaller value caps, just more of them. For example; if you need 100uF @ 25v, try two 50uF@25v caps instead. Using more caps helps transient response.

About the ESC; I know, that's usually the hard part to get (as long as you don't get those LMT motors).

[JThiessen]

That plastic is basically nylon, I'm not certain if you will be able to dye it. That type may be the oil impregnated version (usually referred to as UHMW), but I'd have to double check. It does have a decent strength to weight ratio, but like all plastics, its succeptible to threads pulling out. If anyone else tries to use some, just watch your cutting speeds (it gets to the melt temp fairl quick), and if your drilling keep the speed down, or have it clamped up good as it will tend pull your bit through too fast.

[squeeforever]

If its basically nylon, you should be able to dye it fairly easily.

[BrianG]

I would recommend RIT dye available even at Wal-Mart. There is another major brand that I know of but it doesn't work well at all on nylons/plastics. You could try it on a small scrap first to make sure it won't be all spotchy.

[Finnster]

Hey all. Actually UHMWPE (ultra-high Molecular Weight Polyethylene) is not nylon, that is a different plastic. Unfortunately it does not dye easily like nylon, it is more like polyester, which requires a "disperse dye" and not a simple acid bath dye like RIT. The procedure is simular, but requires an extra activator chemical to be boiled with the plastic. It can be done, just a bit more trouble. I did read somewhere that some use crayons for fabric, then use heat transfer to dye the materials, but the angle shape would be difficult to do this way. ProChem USA has dyes that will do this. ~$5-10 total. Shoot, looks like the only real drawback to this, but I don't really care about the color.

I have to make some corrections to the specs, I needed to look at my notes. UHMWPE is about half the weight of CF. ~.95g/ml, ie lighter than water (floats.) CF is ~1.75g/mL, 6061 is ~2.7g/ml and Titanium is ~4.7g/ml. Steel was 7.5-8 g/ml or so.

If you wanted to screw directly into the plastic you wouldn't want to use machine screws, but more like self tapping sheet metal screws that have a much bigger bite. I have all my screws going into SS standoff nuts and are recessed flat head screws. You can just see the standoffs in pic 3, they go through the 4mm bolt holes in the chassis and provide a 4-40 thread for the screws. There is no way they are coming out. MMC also has 2"x1" U-channels if you wanted to guard both sides of the batt, but the way the batt sits and the extra strap IMO are more than sufficent. The batts are shrinkwrapped, but I did have an experience where a batt shorted on a Alu Emaxx chassis I do not want to repeat.:eek:

Lastly, I don't think the plastic is oil-impreged. Some nylon is, but this is approved for 3A sanitary/FDA usage (dairy and food contact.) It is very slippery tho, close to teflon. This is often used as machinery guardrails, slides and such.

No one else on pinion rec's? 15t it is then? Ack, I need to do some more research. Brian, you had bigger tires on yours w/ the 14t as well, correct?

[Finnster]

BTW, I drilled out all the holes by hand. It really doesn't take much and you really could screw things up by going to fast. Patience is a virtue. :)

[squeeforever]

I would say a 14 or 15T pinion should be about right.