Hi,

I've had some interest from another thread to know more about my hopeful HV conversion of a Jammin X1-CR buggy. I decided to create my own thread about it...

Well, a few months ago I was inspired to get back into RC cars after a 15 year break from them when I last had an RC10 Team Car (which I'm getting running again too). After looking around at what's available these days I was totally amped to get a 1:8 buggy, but at the same time really bummed when I realised not a single manufacturer electrifies their 1:8 models by design. I have never touched an IC engine and intend to proudly continue avoiding them.

Ok, so after looking around a lot I decided to get a Jammin X1-CR Factory Team Edition. I have spent the past few weeks reading, learning, and planning how I am going to go about converting it. I have been flying electric helis for the past 2 years, and in heli land HV is very much the way to go if you want an efficient, high performance heli. So it is my intention to go HV in my car too with the hope of achieving high efficiency and light weight.

After building the rolling chassis I have looked at this from alot of angles. I have considered weight distribution, efficient and neat use of available chassis space, minimum running weight, optimal gear efficiency, gear tunability for track or straight line, and optimal motor RPM.

This is the power setup I am currently shooting for:

Motor: Neu 1912/1Y (825 Kv, 8 pole inrunner, 2500 Kw max)
ESC: Kontronik Jazz 55-10-32
Spur: Custom made 56T Mod1 w/ 10mm face width in Acetal Resin (Delrin)
Pinion: 16-24T (stainless steel, 7mm face width)
Motor/Diff Mount: Custom made, see below
Battery: 2x Maxamps 5S 2100 20C packs connected in series

Why Neu 1912? It is over 90% efficient. It has gobloads of torque being an 8 poler. It has an excellent rep in heli land. Its Kv puts it at 30500 RPM on 10S which makes a wide range of gearing very easy in a car. That RPM also puts the motor at the very peak RPM when iron losses become too great. In heli tests of various motors it has been shown many times over that to get peak performance from a motor a good starting point is to run it just below the point where iron losses cause heat to escalate exponentially. The only downside of this motor are the big gaping holes that will need to be sealed.

Why Jazz 55-10-32? It is the only ESC that has a "car mode", is 10S capable, and can control motors of more than 2 poles (it's been run all the way up to 14 pole outrunners).

I need to up the spur to 56T because the Neu 1912 has a 1.96" case diameter. Although smaller gearing will produce adequate gear ratios, the motor case will touch the drive shafts with all but very tall gearing. My choice of large pinions has a desirable side effect: most gearing is cut with a pressure angle of 20 degrees (including the ones I'll use). At that pressure angle the minimum pinion you can (or should) run is 18T so as to avoid undercutting, wear, and noise.

This is all a very BIG experiment for me. The components I am aiming to use aren't very common in car use at all so I really do not know how this will all perform. I have no reason to suspect it won't work, but I have no experience with converting (or even running) a car on brushless power. :) I only have others' experiences (both car and heli) to lean on and adapt.

Only the Jammin kit has been purchased so far. Right now I am in the process of getting quotes for my motor/diff mount design to be machined, and am also in the process of sourcing the custom spur gear. I will also need to modify the stock steel spur gear to turn it into an adapter plate to which I can mount the custom spur. I hope to get these parts completed within the next week or two.

From there I will order the power system. That will take atleast 3 weeks because it all has to be shipped from the USA.

Well, I've attached a couple of diagrams for you to see. I've tried to design the motor mount in the hope of it being sufficiently strong and light weight at the same time (approx 60g). It is to be milled from a plate of 6061 60x70x9mm. The diff holder is a mirror of the motor mount without the motor section.

Later on I will post my planned component layout on the chassis.

I'm keen to hear your comments and suggestions!!