My e-revo brushless edition build

[MetalMan]

Originally Posted by dave_mackinnon

Shaun.. You can't force current from a car battery.. It's a constant voltage source..

I disagree. It's a power supply, but still a CV source:
http://video.google.com/videoplay?do...lipo+explosion
That is the only Lipo fire I have ever had

Shaun, maybe there is some confusion.. Did you connect the LiPo to a battery, battery charger or power supply?

Batteries are constant voltage - ie: they attempt to maintain a specific voltage independant of load.

Power supplies are constant voltage. I have a 300A 13.5V power supply on my test bench (amongst others) and it attempts to supply a constant voltage independant of load.

Battery chargers vary. The smarter RC chargers work on both Constant current and constant voltage. When you connect a battery, you set a charge current - 1, 2, 5 Amps or whatever. The charger attempts to maintain this current flow to put energy back into the battery as quickly as possible. Good quality chargers use Constant Voltage circuitry to monitor no-battery conditions... Without a battery connected, the device would attempt to produce infinite current as it attempted to push electronics into the air - overly dramatic explanantion... There is some addition adjustment of current at the end of the charge from an intelligent charger.

If you look at the display on the voltmeter attached to that battery, you can see that the voltage was changing as the internal resistance of the pack varied. Odds are, if you were monitoring current - it would have, assuming it was connected to a battery charger and not a power supply, stayed relatively constant.

[shaunjohnson]

i wasnt meaning to go into the math, just off the top of my head i figured a lipo is nearly a dead short...and an electrical setup will draw unlimited amps if avaliable....but for how long!?

(eg, 300 sized brushed motor that has locked up....it's gonna draw as many watts of power it can to try and get going again, hence producing unlimited HP....but for less than a nanosecond!!)

the batt prolly only gave it about 20 odd amps but a lipo is gonna seem like somewhat of a dead short.

and no, a power supply wont work either because it draws way too many amps for a 10A supply to keep up (did that with another lipo).

and the rest of the big epic post you made needs to be put somewhere safe because it is great info...(even know i know most of it) and can be used against the noob forces around the world

lipo fires are old now....all my dead lipo's go in the wood heater now

Noob forces.. I like that! I gotta keep it!

Not sure it was epic.. that would have required research.. ;-)

But, back to topic.. Mistercrash.. We've hijacked your thread.. and now we turn it back over to you! what's next? When you racing next?

[mistercrash]

This is the schedule of the hardcore RC race track for the rest of the summer.

Sunday August 23rd - Open Practice - I will try to be there
Sunday August 30th - Club Series Points Race #6 Finale - I have to be there as I missed point series race #5 and fell to second place
Sunday September 6th - Buggy Endurance Challenge - I don't have a buggy so I'll stay home
Sunday September 13th - Open Practice - I would like to be there and have some fun
Sunday September 20th -Open Practice - I will try to be there and run 6S and try to make the biggest jumps possible and break parts
Sunday September 27th -Open Practice - I will be there if it's not too cold, Traxxas plastic don't like the cold
Sunday October 4th - Truggy Endurance Challenge - I don't have a Truggy so I'll rake leaves
Sunday October 11th – TBA - I might be too busy getting the winter clothes out of the closet
Sunday October 18th - TBA - I might be too busy prepping the snow blower for winter, maybe I will think about converting it to brushless power
Sunday October 25th -TBA - I might be too busy prepping the house for Halloween

[mistercrash]

Update on my ERBE.

The ERBE is holding up very well to bashing and racing, I managed to break a rear suspension arm landing a really big jump and that is about the only thing I have broken recently. I noticed that my Summit shafts were getting quite a bit of slop due to wear. I have been using my ERBE every day since I made all these modifications so I guess this was to be expected. I had a full set of spare Summit shafts so I installed new ones all around, changed a few ball ends on the turnbuckles and pushrods as a precaution and will put new ball ends on the shocks and the ERBE should be ready for the final race of the season this Sunday. My aluminum slipper did so well at protecting my drive train that when the new Summit shafts I just installed wear out, I will put back the stock shafts and see how well they hold up. I am pretty sure that they will do fine with the help of that slipper but we'll see. I haven't done any changes to my connectors yet but I'm thinking about it
Maybe I will find some time to do it before Sunday.
I haven't done any checking of the 8th scale diffs but they are so smooth that I don't see the need to take them out to check them. I have ordered some Losi heavy duty diff cups to install when the snow comes and I disassemble the whole truck for an overhaul.
I am also working on a new 8th scale center diff made with a Losi XXL diff and a different Traxxas gear with a different and easier way to secure the gear to the diff cap.

[mistercrash]

Changing the ball ends on my shocks this morning, I noticed that three of the four Jato shock boots I was using had little tears in them, so I put on three new ones. The Jato shock boots did a really good job at keeping my shock shafts clean but they did start tearing a bit early. I still am going to use Jato shock boots but they do need to be checked and replaced regularly. Just thought I'd let you know. If anyone has experience with other kinds of shock boots, please feel free to share your suggestions.

[Bondonutz]

Yup, same here. I've replaced all mine three times in the 8-9 months. I think the boot gets pinched between the spring coils at full compression ? I'm trying the Bad Horsie Spring covers this time.

Is there a company that makes the shim to go under the shock tower to get a little distance between the shock caps and chassis ? I seen your CF shim but I'd rather just buy something than make something that delicate.

[mistercrash]

I don't believe anyone makes a shim to go under the shock tower, you have to make something yourself.

[mistercrash]

I have started work on a new 8th scale center diff. I have been thinking of ways to simplify the whole process of making one of these CDs and if this thing works and holds up to my abuse, it should be pretty neat. I am waiting on a Losi LST XXL diff to come in. I chose this diff because it has these metal inserts for the spider gear pins inside. It's a very tough diff. Also I like the dimensions of the diff cup, it's a little narrower than the Thunder Tiger or Hyper 7 one so I can use the Traxxas output gear to it's full thickness. I will be using a different kind of Traxxas gear, two aluminum posts with M3 threads in them. I will use a diff and not a center diff, I have made an 8th scale CD using a Losi diff and found out that the ring gear of a diff can be modified just like the spur gear of an 8th scale CD can. Only two holes will have to be drilled through the hardened steel ring gear and they won't need to be threaded, but they will need to be countersunk. And there will be a carbon fiber part on this CD, how cool is that!

[Bondonutz]

Sounds good, looking forward to a update and pictures. Having a abuse resisitant CD is great news !

[mistercrash]

Sneak peak....



I am working on three center diffs at once. I got my hands on an original CowboyRay CD made with a Thunder Tiger S3 center diff and I will fit a 33 tooth gear on it for the ERevo. I have a scjrss CD made with an Ofna Hyper 7 center diff and I will fit the same gear on that and finally I have a MCCD made with a Losi LST XXL regular diff and I will fit the gear on that also. I will do my best to take lots of pics and maybe I will go through the trouble of posting a full materials list for each CD. But for now I have to wait for the carrier pigeon to bring some parts I need up here in Canada to finish those CDs. That pigeon has to go accross the border and the customs people like to shoot them down and do full body searches on them. I hate it when a carrier pigeon comes limping to my door with a sore butt eight weeks after I purchased something from the US.

[Bondonutz]

The sneak peak is a tease for sure, we appreciate your posting this info and build results.

The pigeon has is rough going to Canada Eh ?

[sjcrss]

Sounds great MC...looking forward to seeing your new diff design...keep up the good work man....

[mistercrash]

I experimented with a few options and ideas posted on the net about these diffs.
Two of them I found to be very interesting, a third one was made by a guy in France but it was almost a carbon copy of someone else's. The very first was made by CowboyRay some years ago for the nitro Revo 2.5. This was before Traxxas even came out with their own CD for the Revo. It was made with a Thunder Tiger S3 center differential, the TT spur gear was replace with a machined aluminum cap on which a custom plastic gear was secured with 4 M3 screws. I got my hand on a well used CowboyRay diff and inspected it carefully. The diff is smooth and the cap is very well machined, a thing of beauty. I noticed quite a bit of slop on the output shaft that went through the aluminum cap. Might be that a stronger and harder metal is needed there as the aluminum of the cap wore out and allowed the output shaft to wobble a bit too much for my taste.
The other one was made by scjrss and with his coaching; I made three of his CDs. He came up with a clever solution to secure the Traxxas CD output gear to an Ofna Hyper 7 CD spur gear. The Hyper 7 spur gear had its teeth grinded off to transform it into a cap and 4 holes were drilled and tapped in it matching the holes of the Traxxas CD output gear. The Traxxas output gear could then be secured to the Hyper 7 spur gear (cap) with 4 M3 screws of the right length. A brilliant idea and it works. But the part I did not like is threading the 4 holes in the Hyper 7 spur gear. It’s hardened steel that is probably as hard as the steel from the tap. It can be done but really, it’s a PITA. I noticed some seepage of diff lube using those CDs. It seeps from between the threads made in the spur gear and the screws. Not a lot but enough to annoy me.
Then there’s this guy that came up with a different way. I would like so much to remember where I saw the thread, I have searched and searched and can’t find it or remember where I saw it. If you know about it, please post his name here as this is HIS idea. He made four holes in the 8th scale CD spur gear and counter sunk from the inside. That way he was able to secure four aluminum inner threaded posts with M3 flathead screws and with some minor modifications, the Traxxas output gear could slide on the posts and secured to the posts with M3 screws. This post idea is the base of the CD I did last. I used a Losi LST XXL diff, just a regular diff, not a center diff. And instead of using four posts I used two. For the output gear, I used a different Traxxas gear since the Traxxas CD output gear is not sold separately. Once I was done with this last CD from a Losi diff, I decided to take the time to fit this new Traxxas gear to the CowboyRay CD and the sjcrss CD.
It is good to be as precise as possible when modifying the parts to make these CDs, but it doesn’t have to be down to a thousandth of an inch, you’ll see from the pics that the parts I modified are not perfect. It doesn’t matter because the thing works anyway. We are not touching any internal components of the diff and as long as the output gear is centered on the diff, all is fine.

So lets begin with the Losi CD, first you need a few parts, here is where I found the parts I needed. I give you the links to where I got the parts but you might have other sources to get parts from.

The Losi LST XXL diff, I found and bought it on ebay, I am posting a link but it might not work for a long time, just do a search on ebay for ‘’Losi LST XXL diff’’ and a lot will pop up.

http://cgi.ebay.com/NEW-LOSI-LST-XXL...d=p3286.c0.m14

The output shafts, made from the Traxxas 3.3 Revo CD output shafts. Part numbers TRA5415 and TRA5416. The shaft measurements can be seen on the pic.

http://www.amainhobbies.com/product_...put-Shaft-Revo
http://www.amainhobbies.com/product_...t-Gear-Revo-33

The Traxxas gear, part number TRA3985X. I think they were output gears for the old E-Maxx tranny.

http://www.amainhobbies.com/product_...r-33T-2-E-Maxx

For the aluminum posts, I had a few inner threaded aluminum posts and all I had to do was cut them to the length I needed. To find posts, just search on Tower Hobbies or A Main for ‘’post’’ and a lot of inner threaded aluminum posts will come up for servo trays, steering bellcranks etc. Just find the ones that would be easy for you to cut to the right length. I found these from Axial and I think they would work without any modification to them.

http://www.amainhobbies.com/product_...mm-Post-Grey-2

Two 8X12X3.5 mm bearings

http://www.amainhobbies.com/product_...all-Bearings-2

8x10 mm shims and 6x8 mm shims to center the CD perfectly in the tranny.

http://www.amainhobbies.com/product_...mm-shim-kit-10
http://www.amainhobbies.com/product_...6x8mm-Shim-Set

1.5 mm thick carbon fiber. Aluminum or other kinds of metal can be used also. Even a simple washer of the right size.

http://www.fullforcerc.com/Carbon.htm

Four M3x6 mm flathead hex socket screws. No link here as I am sure everyone has a place to get them, hardware store, LHS or online.

Here’s a link to some carbide bits that will help tremendously in drilling and counter sinking the holes in the ring gear

Drill bit
http://www.usacarbide.com/catalog/pr...ducts_id=17778

Counter sink bit
http://www.usacarbide.com/catalog/pr...ducts_id=17916