Hellfire conversion

lol, yeah, about 5 minutes worth of fun!

I had the same powertrain on my Revo conversion, and was able to run through most of the pack before needing to stop for a cooldown. I'm not quite sure why it's running so much hotter in the hellfire. Perhaps the CD is unloading too much ?

I'm sort of holding off on a new motor purchase until the Monster Max combo shows to be stable enough for me to spend money on. I'm thinking the castle neu should be pretty good for my application on 4s. I would love to spend the money on a 1515 right now, but I just can't.

This is not my first RC, or my first conversion. I have 2 revo's that I've converted, a heavily modded e-savage, and a heavily modded emaxx. that's just a few of them. I have quite a collection of tamiya's as well.

I'm just still a bit baffled by the hellfire heating things up so quickly. I was scared of burning up the 9920, so I switched it out for the 125b that was running on the emaxx. I expected the 125b to run a bit cooler than the 9920 on the same setup, but it seems that is not the case. Does anyone feel the 13/52 gearing is incorrect for this setup ? I know I need to tape the tires and such, maybe that will help. Also I'm sure heavier diff fluid in the center couldn't hurt.

[Arct1k]

Are you using an UBEC - It only has a linear bec so 4s will generate a fair amount of BEC heat.

Is the case "hot" all over - Do you need to do the internal mod? It could be worth looking at the RCM heatsink or just using an aftermarket one.

I managed to thermal mine on a buggy on a v hot day - I've geared down a bit and added a couple of 40mm fans...

30k in the middle is a good start

I am using a CC BEC. I won't risk running a quark 125 at any voltage withough one. They're hot enough as it is. I'll look into some 30w for the center. It does seem the front is unloading a bit too much for my taste. I'm sure that could result in some extra heat. It does indeed seem to be "hot all over". Not like the thermal transfer pad inside has failed or something. The case is hot enough, but it's much hotter on the PCB where the motor wires are soldered in.

J.

[BrianG]

I find the thermal performance of the quark to be acceptable only after the "internal mod" and adding extra heatsinking (and if you insist; fans). Once that is done, it runs well. You just run the risk of messing it up. You could try adding a couple/few extra capacitors to the power input line as well.

However, the hellfire probably is kinda heavy and could benefit from the added efficiency and power of 5s. Then you can gear down to reduce the load on the system.

As far as the diff unloading goes, I used 50k in the center in my Revo (using an 8th scale style diff, not the Trx one), and it still unloaded too much.

yeah. the hellfire doesn't unload the way that my revo did with center diff, but it does unload quite a bit. I can still get a bit of a wheelie out of it though, so it seems about right to me. There's more weight up front on the hellfire than the revo, i'm sure.

I know about the quark and thermal problems, but it ran cooler than this on my very heavy emaxx. I don't know for sure. I'm going to start tearing it down tonight and see what I can come up with. I'll also probably do the thermal mod on the quark to try and get her running a bit cooler, and check all the diffs.

[BrianG]

I wouldn't go through all the work of tearing it down. Just remove the pinion (or adjust the mesh so the pin/spur don't touch) and spin the CD to see how free it is. There is some gear drag, but the tires should keep moving a little after you spin it manually. I think it's a factor of the greater weight of the truggy vs a maxx. What speed do you have it geared for?

It's geared for about 35mph. There is a bit of drag on the CD, i noticed before putting everything together. Also there is a sort of ticking sound from the rear while free-rolling without the motor attached. Doesn't seem that the rear diff slips under power or anything though. No strange noise under acceleration at all. Also, I think my maxs is heavier than the hellfire. I'm just guessing, but with all the aluminum on the maxx it's quite a beast.

J.

[JERRY2KONE]

Whats your EMaxx setup? Which version do you have? Just from your photos I would think that the Hellfire is a liter setup as well. Are you sure that you dont have a small short of some kind going on there? I am sure that you will get to the bottom of that one. Good luck with that.

the emaxx is all unlimited engineering stuff. Chassis, arms, etc. It's too heavy to do much with, but it sure looks nice, lol.

I havn't weighed them, but I'm pretty sure the hellfire is lighter. I took the electronics and motor off the hellfire last night. I think there's a bit more resistance than there should be when rolling it. Going to check the gear mesh in the front/rear diffs over the weekend.

I'm sure I'll get it worked out. I'm just bound and determined not to spend any more money on ESC's until I can get my hands on a working Monster Max. Having been through 3 quark 125's and 1 mgm16018 i'm just not going to spend that kind of money on an ESC again.


J.

Yo Brian,

You know what weight oil is in the diffs ? front/rear/center ? Just curious.....


J.

[BrianG]

Have no idea. It's been a while...

I don't know if I've resolved any issues, but I've re-designed my chassis layout.

- flipped diff (positions motor to front and left)
- Moved battery to back right
- Make aluminum battery tray/holder (doubles as rear chassis stiffener)
- Move radio box to back left

The battery tray / chassis brace worked out great. I'm very pleased :). Finally, an effective way to stiffen the rear after losing the upper deck on the hellfire. I'll get some pics up later tonight. Just need to finish up some touches on the tray, and I have to run a few errands first :|.

I had the front and rear diffs opened up. There is indeed a good bit of wear on the crown/pinion. It looks like unusual wear. As if they were run for a time with bad mesh. I will probably need to replace them sooner than later. It seems there is more drag in the front and rears than I would like. These are my first 8th scale diffs though, so I have no basis for comparison.


That's it, wait for pics!

J.

[JThiessen]

I'm really looking forward to getting mine converted now. Its been sitting in a box for almost a year. Now that I have the Gmaxx and ERevo up and running, I should have some time for it.

Here's how she sits now. At least you get the idea of the basic layout. Quite a big change from what was there in the earlier pics. I think the balance will be better, and certainly some strengthening of the chassis is added. The battery tray is attached with M5 screws which are tapped into the chassis. You may notice the battery will sit much lower now, and there's some more weight up front. The motor mount is the lightning mount from RCM. The chassis holes did not line up, so I got the matching bulkhead from tower, and mounted the pair to an aluminum plate which I then bolted to the chassis.

I also put some 300k oil in the center. Perhaps that will help with my pizza cutters up front :D. I'm gonna give it another shot with the 8xl and BK and just be easy on it. I'm trying my best to hold out until I can grab up a castle built NEU.

I hope you're using velcro under the battery as well so it doesn't slide forward and back. but looks really clean.