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 :party:

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.

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:yipi:

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

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?

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

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 :mdr:
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.

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.

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.

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

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!

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

Sneak peak....

http://i177.photobucket.com/albums/w...iff/mc_cd1.jpg

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.

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 ?

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

The birth of the 8th scale Revo CD
 

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

I started by modifying the Traxxas TRA5415 and TRA5416 Traxxas output shafts. You cut the gear part off and have to drill a 2.6 mm hole for the spider gear pin. The tricky part is having the hole perfectly centered in the shaft.

http://i177.photobucket.com/albums/w...16_shafts1.jpg

Here are two of the TRA3985X Traxxas output gears, you see them with the flat side of the spokes up. The left one is stock and the right one has been drilled in two holes with a 6 mm bit. If you use the Axial posts I linked above, the holes will have to be 7 mm or 9/32 inch. There are two of the gear’s spokes that are thicker than the rest. The holes have to be drilled next to those thick spokes and which side of the spoke you drill is also important. I drilled according to the rotation of the gear inside the tranny, I wanted the forces exerted to the gear to be transferred to the posts from those thick spokes. The center hole has a little ridge that was cut off to allow the 8X12X3.5 bearing to sit a little deeper in the gear.

http://i177.photobucket.com/albums/w...f/th_mccd1.jpg

The two inner threaded aluminum posts that will be screwed to the diff cap. The length on the posts is about half a millimeter less than the thickness of the Traxxas TRA3985X output gear.

http://i177.photobucket.com/albums/w...f/th_mccd4.jpg


Now to start modifying the ring gear. I make the holes and I counter sink them first. To make sure that the holes were in the correct position, I used the Traxxas output gear and aluminum posts as a template. I slipped the two posts in the holes I made in the output gear and the 8X12X3.5 bearing in the center hole. The bearing is there just to center the gear perfectly on the ring gear. An 8X12 bushing would work also but I couldn’t find one.
I take the Traxxas output gear with the posts and bearing and I slip it on the ring gear, I rotate it to center the posts between the screw holes of the ring gear the best I can and with a 2.3 mm drill bit chucked in the drill press, I go through the posts and make contact with the ring gear. The 2.3 mm bit will not touch or damage the threads in the posts, this is just to make a couple marks on the ring gear to show me exactly where to drill the 3 mm holes with the carbide bit. I take off the Traxxas output gear and then I can make the holes and counter sink them.

http://i177.photobucket.com/albums/w...f/th_mccd2.jpg

Then I take a 6 mm threaded rod I have and with two nuts and two washers, I secure the ring gear to the threaded rod. I can then chuck the rod in my drill press and with an angle grinder, I grind off the teeth until the gear is left with a half millimeter lip that will fit over the diff case.

http://i177.photobucket.com/albums/w...f/th_mccd6.jpg http://i177.photobucket.com/albums/w...f/th_mccd8.jpg

This step is optional; I chuck the threaded rod in a power drill and with a belt sander, I can clean up the marks left by the grinder.

Here’s the finished ring gear from both sides, now transformed into a cap. You can see the counter sink holes on the inside of the cap.

http://i177.photobucket.com/albums/w...f/th_mccd9.jpg http://i177.photobucket.com/albums/w.../th_mccd10.jpg

We’re ready to assemble the center diff. I start with securing the posts on the ring gear with the M3X6 mm flathead screws. I put blue Locktite on the threads.

http://i177.photobucket.com/albums/w.../th_mccd11.jpg http://i177.photobucket.com/albums/w.../th_mccd12.jpg

Then I put the 8X12X3.5 bearing on the cap. Here you can see a shim underneath the bearing, you can do without it. I had the shim so I used it, it just positions the bearing in the middle of the output gear.

http://i177.photobucket.com/albums/w.../th_mccd13.jpg

I assemble the diff with my choice of diff lube. I like to run 100k for a stiff diff. On 4S, this lube is thick enough to allow some wheelies but unloading to the front is minimal. 50k will give you a looser diff with more unloading to the front but on 4S wheelies are practically inexistent.

http://i177.photobucket.com/albums/w.../th_mccd14.jpg

I slip on the Traxxas output gear over the posts and bearing.

http://i177.photobucket.com/albums/w.../th_mccd15.jpg

Now for the carbon fiber disk to hold the gear in place with two M3X6 mm flathead screws.

http://i177.photobucket.com/albums/w...f/th_mccd5.jpg http://i177.photobucket.com/albums/w.../th_mccd16.jpg

The last part is one of the plastic spacers that come with the stock output gear and shaft of the ERBE. I sanded it down to the right length and it serves as a spacer so the CD can butt against the bearing in the tranny case.

http://i177.photobucket.com/albums/w.../th_mccd17.jpg

I slipped it on the output shaft and in the carbon fiber disk until it is well seated against the cap and put a drop of CA glue to glue it to the carbon fiber disk.

http://i177.photobucket.com/albums/w.../th_mccd18.jpg

Now install the CD in your ERBE and enjoy some trouble free CD action for racing. Next posts will be the Traxxas TRA3985X output gear installed on the scjrss and CowboyRay CDs.

As always, MC, you have done something nothing short of amazing!

Awsome, Just Awsome. Any chance of you selling these?

And if not how would you perfectly center the hole in the output shaft?

Very nice MC, I like the new design.....great job

I made a simple jig from a piece of 1/2'' X 1'' X 2'' steel. The jig has to be made very precisely, if you can make it with good precision then it will help you have perfectly centered holes in your shafts every time. I just put the output shaft in it, flush with the surface, tighten the set screw so the shaft doesn't move, I put the jig in a drill press vise much like this one and drill in the hole of the jig which guides the drill bit.

http://i177.photobucket.com/albums/w...t_hole_jig.jpg

I FOUND IT!!!!
Here's where I got the idea, it was ''its-me'' that came up with the idea of the posts. I was sure he used 4 but apparently he used two. So finally, thank you its-me for the brilliant idea.

Here's the post
http://monster.traxxas.com/showpost....&postcount=336

TRA3985X output gear on the scjrss CD
 

So here's how I installed the Traxxas output gear on the Hyper 7 CD that scjrss made. Here's the cap made from the Hyper 7 spur gear with the 4 holes that are threaded with M3 threads.

http://i177.photobucket.com/albums/w...scjrss_cd1.jpg

The red you see in the holes is just something I am trying to stop lube seapage between the threads and the screws. It's very sticky and tough tape used to tape the seams when you put vapor barrier on your house's walls.

http://i177.photobucket.com/albums/w...scjrss_cd2.jpg

Here's the CD assembled ready for the output gear.

http://i177.photobucket.com/albums/w...scjrss_cd3.jpg

Other than the center hole that was trimmed to let the 8X12X3.5 bearing go deeper in the gear, it didn't need any more modifications. The thick spokes of the output gear are lined up between the threaded holes of the cap.

http://i177.photobucket.com/albums/w...scjrss_cd4.jpg

Four M3X16 mm flathead screws that were trimmed down to 14.5 mm in length to secure the output gear to the CD.

http://i177.photobucket.com/albums/w...scjrss_cd5.jpg

And here is the final product ready to use.

http://i177.photobucket.com/albums/w...scjrss_cd6.jpg

TRA3985X Traxxas output gear on the CowboyRay CD
 

Finally here's how I put the Traxxas output gear on the CowboyRay CD. Here's three shots of the machined diff cap. This is a well used cap so that's why it looks a little grungy.

http://i177.photobucket.com/albums/w...boyray_cd2.jpg

A shot of the stock Traxxas output gear on the left and the modified one on the right. Some grinding was needed in the spokes for the screws to meet the holes in the cap and some grinding of the spokes from underneath the gear so it would fit on the cap's elevated portion.

http://i177.photobucket.com/albums/w...boyray_cd1.jpg

Here's the CD assembled.

http://i177.photobucket.com/albums/w...boyray_cd3.jpg

And here is the output gear on the cap lining up with the cap's holes for the screws.

http://i177.photobucket.com/albums/w...boyray_cd4.jpg

The finish CowboyRay CD with the Traxxas output gear using 4 M3X8 mm flathead screws to secure it to the diff cap.

http://i177.photobucket.com/albums/w...boyray_cd5.jpg

Are all of these CDs for the e-revo? I would really like another CD option for my nitro conversion. The LST diff option definitely looks like it would be easy to make. Great job btw.. the diff looks great.

Sick, just sick!

Yes, they are all for the E-Revo.

MC could SAE drill bits of similar size also be used? If not any places in Canada (winnipeg, mb) that I might find a 2.6mm, 3mm and the countersink locally? If not does that site you linked have a 2.6mm bit?

The site I linked has a 2.5 mm straight flute carbide bit but not a 2.6. This site has a 2.6 mm Tungsten carbide bit, but it says it's a drill bit and not a straight flute bit. It will do the job but a drill bit is more fragile than a straight flute so you have to be careful and go slow, especially when the tip of the bit is just about to go through the piece you're drilling. I made 3mm holes for 3 mm screws but a 1/8'' bit would do the same job as it is 3.175 mm. Close enough IMHO. I don't know of any places in Winnipeg to find carbide tools.

I have a CD I made for my nitro Revo using scjrss's method but with Thuder Tiger S3 buggy parts like the CowboyRay CD. I will look into making a new CD for my nitro Revo with the Losi LST XXL parts and the ''it's-me'' post method. I will see if I can use the output gear from the nitro Revo Traxxas CD or maybe adapt a different Traxxas gear that has the same tooth count. Or maybe just use the same gear CowboyRay used.

So then for the 2.6mm would a 7/64 (2.78mm) work for the output shaft?

The real measurement of the hole for the spider gear pin in the shaft is 2.5 mm. I went with 2.6 because it gives me a little more play just in case the hole I made is off by a thousandth or two. If you have a way of making an absolute centered hole in the shaft you can use a 2.5 mm bit. If you're like me and your work is ''precise enough'' :mdr: then I suggest a 2.6 mm. 7/64th or 2.78 mm is too big IMO, the pin will wobble in the shaft too much.

It took me more than 4 hours total but I finally did it. My ERBE is now running with 5.5 mm bullet connectors.

ESC bullets
http://i177.photobucket.com/albums/w...th_bullet1.jpg

Ready to go with a couple 2S packs plugged in
http://i177.photobucket.com/albums/w...th_bullet2.jpg

The parallel harness
http://i177.photobucket.com/albums/w...th_bullet3.jpg

Now I don't know what to do next on this ERBE. I think I covered just about everything and addressed a lot of issues. The thing is running so well now when I race or bash it. I'm out of ideas, I need to get a new RC. :mdr: How about a Losi 8ight E 2.0 buggy.

If your just bored you could put some heat shrink tubing on the female side of the motor connectors on the esc. Anything metallic gets up in there and hits two of those motor connectors and poof! goes the esc:mdr:. I think that could be one of the reasons some MMM's mysteriously die.

Thanks for the project that will occupy 10 minutes of my time :whistle: :mdr: But seriously, really? I never thought about those female connectors sticking out of the ESC. Can they really be shorted out when batteries are plugged in? If yes then I will certainly put heat shrink on them.

I would assume that would short it out, I'm not gonna test it on mine though:tongue:

I don't think they can be shorted by a piece of metal, I mean if they could, the ESC would have been done differently. The ESC motor bullets would be covered if they could be shorted. Maybe a tecky can clarify this? please.... pretty please... :oh:

Im not sure on the motor wires but that is why that got rid of them on the battery side. The female ends were bending in and touching the heatsink and shorting it out. Thats why the went to the battery wires straight to the board.

Id go with the Losi buggy next. I love mine handles so great.

Yes that Losi buggy is very tempting. Well even if there's no confirmation on the possible shorting of the motor leads, I had to open the ESC to clean the inside and check the fan anyway so I went ahead and shrinked them. I also have a used MMM system as a spare so I wanted to see how difficult it was to open the motor to check the bearings. I had a little trouble getting the end caps off the motor and they got tiny marks on they from the process but I got them off. And yes, one of the bearings needs to be changed. I took the opportunity to change something to the front end cap, I drilled and tapped the mounting holes to 4X0.7 mm threads. Then I drilled the holes of a spare motor mount to 4 mm and counter sunk them to accept M4X10 mm flat head screws. I had that motor come loose on me once but I was lucky as no damage was caused but it could have been worse. M4 screws will hold the motor a lot more securely to the motor mount IMO. I saw someone else do this and I thought I'd give it a try.

I'll ad pics later today.

Here's the pics, first the shrink on the motor tabs. I know they're blue, they match the boots on the shafts.

http://i177.photobucket.com/albums/w...sc_shrink1.jpg

And the M4 screws for the motor to attach it to the motor mount.

http://i177.photobucket.com/albums/w...mount_4mm1.jpg http://i177.photobucket.com/albums/w...mount_4mm2.jpg http://i177.photobucket.com/albums/w...mount_4mm3.jpg http://i177.photobucket.com/albums/w...mount_4mm4.jpg http://i177.photobucket.com/albums/w...mount_4mm5.jpg http://i177.photobucket.com/albums/w...mount_4mm6.jpg http://i177.photobucket.com/albums/w...mount_4mm7.jpg