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Planning E-Revo
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Pliska
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Post Planning E-Revo - 08.27.2007, 12:39 AM

hi guys,

I am planning on building an erevo,since i have no local racetrack it will be a basher,I have a 2.5 chassis with rpm arms and lunsford rods,buckles and pins. I am planning on useing a 8Xl motor with a Mamba max esc. Rc-monster motor mount and heat sink. I am going to use some novak fans to keep everything cool.

I am planning on locking the stock tranny in second(i have done a FOC). and useing the mechanical brake. I will be useing the stock rx pack/radio and reciever, until i can upgrade to a Dx3 and use a ubec. I want to Run two 2s2p Lipo batts. I was thinking about getting two http://cgi.ebay.com/Turborix-7-4v-20...QQcmdZViewItem Will these work for my appications or should i just get some maxamps 2s2p lipos?

I havent figured out what to build the battery tray out of. I will be looking around this site for some ideas. Probably on the right side..

Is there anything I am missing in my BL Revo setup? any ideas or info would be great, this is going to be my first electric setup and i want to make sure i got everything.
   
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nieles
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08.28.2007, 10:54 AM

if i were you i would use maxamps or true-rc packs.

if you lock the tranny in 2nd you could also use the motor brakes
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riceman
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08.28.2007, 05:14 PM

Sounds like you are well on your way. I'd be very wary about trying to save a few bucks and going with a no-name lipo. These things are finicky enough without having to worry about quality. For bashing Maxamps are pretty hard to beat. As for trays, people here are quite resourceful and you can get a lot of ideas by looking at the different built threads. I have a few different conversions and every one of them has a different battery tray. One fabricated out of aluminum angle, another hacked out of an e-maxx chassis, and another using Kyosho Twin force trays (which are available through Mike).

My Revo is set up for racing and I use first gear and mechanical brakes. 3S is plenty for my track and I can get a 15 minute main out of a 3S 6000 mah pack.
   
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Pliska
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08.28.2007, 07:24 PM

hey,

Thanks for the reply, I think im going to just save up and get the maxamp lipos. I will check out the Kyosho twin force trays.

So I havent missed anything I need with my setup? Reason im saying is because I have to order everything online and dont want to be without something i need.

I will be getting a Mrc 989 for the charger and useing a cell balancer. I have to use a cell balancer with any charger right?
   
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jnev
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08.28.2007, 07:46 PM

Quote:
Originally Posted by Pliska View Post
I will be getting a Mrc 989 for the charger and useing a cell balancer. I have to use a cell balancer with any charger right?
Correct. Or at least it is recommended so you can keep your lipo batteries in good shape... so its a good investment. I use the 989 charger right now actually with a Hyperion LBA10 balancer, and it works perfectly. Can charge my 4s 8000 pack great and any other misc. batteries I have had.

The Twin Force trays may be weak if you only bash. Mine actually cracked in half on my 1/8 buggy, and got my battery pretty banged up too. For my last 2 trays, I have made it out of sheet metal. Just fold all the tabs up, and round the corners and you are done. Very secure. I also have a few Velcro straps and zip ties that can be used over many times to secure the battery in place.


   
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Pliska
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08.28.2007, 08:28 PM

Hey

I didnt think of useing Sheet Metal, My dad works with it all the time so i can get some for free(hes an Hvac tech), Thanks for the tip!

As for gearing i was thinking about useing 36t mod1 spur and a 20t Pinion, according to the speed calculator it should put me at around 40mph, does this look good?:
Differential Ratio: 2.8461538461538462
Transmission Ratio: 2.2941176470588233
Other Ratio: 1
Spur Tooth Count: 36
Pinion Tooth Count: 20
Total Voltage: 14.8
Motor KV: 2084
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0073
Spur/Pinion Ratio: 1.8 : 1
Total Ratio: 11.75294 : 1
Tire Circumference (inches): 18.06 inches (458.83mm)
Total Motor Speed: 30843.2 RPM
Vehicle Speed: 44.89 MPH (72.11km/h)
Effective Speed Rate: 3.03mph/V (4.87kmh/V)
Effective KV Value: 2084

Last edited by Pliska; 08.28.2007 at 09:01 PM. Reason: gearing question
   
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BrianG
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08.28.2007, 08:45 PM

If you want a simple sheet metal battery tray (aluminum preferably for weight), you might want to take a look how I make mine. Just click the BL Conversions link in my sig. All my conversions use the same scheme, except the Revo...
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Pliska
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08.28.2007, 09:07 PM

Very nice BL conversions Brian, What did you make them out of, Aluminum metal sheet and just pound it in place?
   
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BrianG
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08.28.2007, 09:53 PM

Thanks. Yeah, 6061-T6 ~2mm thick Aluminum sheet. Make sure it's T6 or you'll get stress cracks on the bends. I just cut it out with a dremel/hacksaw/nibbling tool, file the edges, pound/bend into shape with a vice and hammer, and paint.
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Pliska
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08.28.2007, 10:30 PM

Thanks for the info

I think I will go with a battery tray like that, it looks real nice but not too hard to make.

What do you guys think about the gearing? 36T Spur 20T Pinion work? I would like to stick to the mod1/Stock slipper, trying to use as many stock parts as possible
   
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nieles
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08.29.2007, 03:33 AM

the gearing is good, but also order an 18t so you can play a little bit with the gearing(or an 38t and 40t spur)

in your calculations you have to use around 3.4-3.5v per cell because of voltage drop. other than that it seems like you are good to go
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BrianG
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08.29.2007, 09:55 AM

IMO, that 20T pinion on 36T spur is geared kinda high with the tranny locked. You might find the ESC/batteries get warm, especially with a lot of stop and go action.

If you keep the 2 speed tranny, it would place a lot less load on the motor on take-off, yet give you good top end. Although, I don't know how the stock shift clutch will hold up to BL power. This assumes of course that you keep the servo brake and not have reverse...
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Finnster
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08.29.2007, 12:09 PM

I have a 8XL/MM using the stock tranny and I have found the beast gear ratio to be about 16.3:1 on a 10lbs Revo. The motor and esc are nearly the temps the same, tho both climb up if I'm running hard (as all Xl motors will do.)

11:1 is far too low IMO. I have a manual brake, but I use heavy tires Maxx Mashers on beadlocks). I would def lock in 2nd. You'll have plenty of power and a reliable tranny w/ motor brake and reverse if you want it later. I'll think the 8XL will shred the OWB on the first gear quickly enough. The revo has a pretty adjustable tranny, so pick a pinion that puts you in the middle of the possible ranges so you have some room to tweak. Personally I use a 16/40 with 39t 2nd gear in the tranny (I already had a 16T pinion.)

Lastly i would also look at the TrueRC batts also. I use them and love them. They have very similar performance to the Maxamps, but way cheaper. The 4S2P 6400 pack is the std 44mm width and $160, or the 4S2P 8K pack is also great @ $150, tho its a touch wide @ 50mm, so plan accordingly. Don't worry too much about their C-rating, its way underrated (nice change for once.)I've owned both and can vouch for their performance. Both Vids in my sig are on the TrueRC packs. The 4s on 6400 packs, the 5S on 8k packs. A single 4S pack will be much easier to charge and balance than a 2x2S if its not being used elsewhere.

Speaking of lipos. I've read a few times about people having problems w/ one of the MRC chargers w/ lipos, that's its not cutting off the charge @ 4.2V, but is going a bit higher IIRC. I know the Astro109 is an awesome lipo-only charger, as is a cellpro. For an all-in-one the Triton2 is good and inexpensive, while the Hyperion charger, the Thunderpower 1010C (w/ V2.3 update), and the Xtrema are all very good all-in-ones. Many of these can charge A123 M1 Li-ion cells as well, and are not that much more than the 989.

For the calc parameters, I use 6.5-7" tires and 3.5V/cell and it puts #'s close to my radar gun. You should get 38-42mph realworld, depending on weight, etc.

Last edited by Finnster; 08.29.2007 at 12:19 PM.
   
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Pliska
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08.29.2007, 12:34 PM

Thanks for the replys, I will be locking it into second, so I will try out the gearing Finnster said, as well get a few other pinions. He has almost the exact same setup as I will be running. I already have some extra 40T spur gears so that helps me.

As for the Lipo, I will check out the 4s2p packs, I think that will be the way to go, so i dont have to mount two batterys/charge two and run the wiring for two, I think one will be more simple. I am going for as simple as possible for ease of working on it.

I will look into the chargers before I decide on witch one I will go with. Thank you all for the insite!
   
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lincpimp
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08.29.2007, 05:27 PM

With the 4s2p keep in mind that weight balance will be off on that side. That being said there is not alot of real estate to mount 2 battery packs on a revo with a stock tranny. The emaxx chassis really makes nice trays. I found a new chassis on ebay for about 15 bucks shipped and a few minutes with the band saw got me two nice strong battery trays. Just a thought.
   
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