Jammin X1-CR HV conversion
 

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!!

All sounds cool, with only one hesitation in my mind.

How many spurs you gonna have made and at what expense? Could you use much more widely available Ofna 51t spurs (and diff) With LSP r&p and large motor pinions? That should give you enough clearance as well as plentiful (and cheap) spur gear availability.

It should be an awesome conversion. Good luck with it.

Sounds like a nice project! Good luck and keep us posted.

Very interesting conversion you have planned. Its WAY outside the box!!

Just some quick questions that come to mind.

It sounds very heavy with 10s and that big motor. Is that heavy of a power system really necessary for a buggy? Most find they have more power than they need or can use with the Neu 15** series motors. It sounds more like a heavy Monster Truck setup.

I am very curious to hear about your experience with the the Kontronik Jazz 55-10-32 ESC. I dont know much about it but it sounds like it has some very impressive capabilities.

I gree w/ CoolHand... Could you use the 51T Ofna Spur? They make them in Delrin and if you want more strength could you just mount 2 of them against each other to double the surface area.

Killer project tough... I cant wait to see the progress!!!

On the spurs, they will cost about $30. It becomes exhorbitant if they wear out or continuously strip, but assuming they have a long life it's not a big deal to cough up the extra cost. Given 7mm face contact width, acetal resin material, and hopefully no undercutting from the pinion, I am banking on them lasting a long time. If they don't I will need to rethink my design!! :)

I have considered the 51T Ofna spur. There are a couple troubles with it. First there are no published measurements of it regarding the spacing and size of its mounting holes and they're not a stock item in car hobby shops here for me to go look at. I plan to use the stock 48T spur as an adapter plate which leaves only a few mm of tolerance for drilling extra mounting holes without sacrificing strength - the 51T might be too small and too thin around its outside for mounting like this, and its small size would probably require me to machine away the teeth of the stock spur so that they don't get in the way - with a 56T spur I can leave them behind and just drill 4 mounting holes. At 51T my low speed gearing options will be limited until the motor case touches the drive shafts. It will also mean using smaller pinions which exceed a pressure angle of 20 degrees.

With my intended pinion range of 16-24T I can gear for 30MPH to 50MPH. With a 16T there will be about 3-4mm of clearance between the motor case and the drive shaft, which leaves me with some breath room to add a cap to the front of the motor to seal its big holes.

The 1912 is the same power rating as the 1512 but is 2 oz. heavier. I have considered the 1910 to save weight, but it would have a big drop in max power and from what I've read 2000+W seems to be what you need in a 1:8 buggy?

The packs will add 500g of weight. I got the impression that 4S 8000 MAh was common in buggies, and those weigh 725g...

The really nice thing with the maxamps 2100 cells is that they are only 100mm in length. That will let them mount very nicely in my chassis without them pushing up onto the dust guards. I will post a diagram of my planned component layout a bit later...

Thanks for your input!

Made a quick diagram of the component layout. You will need to use your imagination because the photo I took was not from directly above, so the battery packs look like they'll clash with car components. They should fit perfectly, however. :)

I am interested in how that neu does. Keep us updated.

Aragon,
If you need some demensions on the 51T spur gear let me know. What you should see in the pics below, is a Hyper 7 center diff, with a 51T Ultra MBX spur gear. The adaptor you see there is from JT Racing. The adaptor was originally ment for the 62T dominator Steel gear, but the 51T delrin spur from the ultra series buggies fits just fine. Someone should suggest to Mike to order 20 to 30 pieces, bet they will sell on his website.

http://img387.imageshack.us/img387/4...d51tspuux2.jpg
http://img365.imageshack.us/img365/5...spurbottn0.jpg

Aragon,
forgot to mention the hyper 7 diff fits in the MP-7 series buggies, Hyper series buggies, jammin series buggies and Hot Bodies series buggies. Not for mugen.

That is very nice. What you've done is essentially what I plan to do with the stock spur to convert it into an adapter plate for a custom 56T spur. The 56T is big enough to clear the teeth of the 48T so all I'll do is drill 4 mounting holes in the outer edge. It will look a bit like a 2 speed gear when done.

Your photos are very clear, thank you. Could you measure the diameter of the Hyper 7 diff casing please? I will keep this route in mind.

@vad

Can you post or PM me the dimensions of the 51t spur?

Mike makes those adapters himself. have you got a partnumber of the HR adapter?

a 51t mod1 spur is 53mm according to brian's calculator.
http://www.scriptasylum.com/rc_speed/_gear_calc.html

Mod1 gear diameters are easy. Just take the tooth count and add 2 and you have the gear diameter in mm.

32P and 64P are not quite that simple.

Yea, the outside diameter is the easy part. It's the dimensions/positioning of the mounting holes and the size of the bore that isn't...

51T spur gear is 53mm x 6.7mm

I dont have a part number, I just email Tad from JT racing and tell him I need the spur gear adaptor for the hyper 7 diff.

The diameter is 30mm.

Hi

My project is progressing slowly. Got my motor mount from the machinist today. Couple of issues to sort out, but it's coming together atleast.

I've posted some photos here.

Looks good!

Looks nice so far. As an aside, where in Cape Town are you? My father in law was born and raised in Cape Town (lives in US now tho), and my first trip there was last year with my wife to visit some of her family and see the amazing sights.

Cape Town and the whole western Cape is about the loveliest place I've ever been to. My father in law now has a retirement home in Langebaan I plan on visiting as much as possible. :)

g/l

[IMG]http://img110.imageshack.us/img110/8...1924bi7.th.jpg[/IMG]
[IMG]http://img339.imageshack.us/img339/9...townrb5.th.jpg[/IMG]

Hey Finnster,

I stay in a town called Hout Bay. It is in between Camps Bay and Kommetjie. Love it here. :) A lot of South Africans migrate to the UK or Australia due to the bad job market and crime here, but most of them return after a few years. If you're ever in town we should hook up. This place is in big need of more BL cars. :D I think I'm the only one in the country contemplating a 1:8 conversion.

I'm into Slope Soaring too. I made a vid a while ago with some Cape Town scenery that you might like:

Video (XviD encoded, 14 MB)

http://img228.imageshack.us/img228/1...0306pc3.th.jpg
This Hout Bay? :):P

On our stay, my father in law gave us the exec tour of the W Cape, and one day we went round from Camps Bay to Kommetjie, and then over to Simon's Town and down to Boulders to watch the penguins. We stopped in Hout Bay and ate lunch at a restaurant on the docks and watched the seals in the bay. Lots of great photos all along the way.

Very nice vid BTW. I could see flying planes alot easier there. Not a whole lot of space for cars between the mountains and the ocean. The ever present winds could get tricky but fun tho. We went up Signal Hill on new year's eve (1st pic on post #22 for other readers.) Between the sights and the music of the minstrels coming up from the bo-kaap, the whole experience was surreal. Saw lots of kites, but no planes.

Lastly, that's pretty much what my FnLaw did. Went to UK after University, met Mom in law, lived in UK for a while, then came to US ~25-30 years ago for better jobs. Just retired, bought house on Saldanha Bay, but between having family in US, Brit wife, and ensuing immigration issues, they only can stay there 3mos per year. (Not to mention SA would want to tax his pension if he renewed his citizenship.) If I was ever to leave the US, Cape Town would be the very top of my list of places to go to. At least there is a welcoming home to stay in anytime we want it.:) Strangely enough, their other house is near Chester, NY, where RC-Monster hosts its yearly brushless bash at Barnstormers R/C. What a small world....

Lov to meet up anytime I got there (may be a few years,) but the wife already gives me strange looks when I drag the R/Cs all over. Taking the Revo 10,000 miles to Cape Town might be a bit much for even her patience. :D


Back to the R/c thread....

Yup, that's Hout Bay in the distance! I dabble in a bit of RC AP sometimes. Took some shots of Hout Bay a while ago and posted 'em here. It should bring back some memories. Sounds like you had lunch at Snoekies or Mariner's Wharf. :)

Small world indeed. Small town this too. :) Good to make your acquaintance!

Hi,

My experiment is progressing slowly. I received the mounts back from the machinist again and the bearings fit great now. Latest pics are in my RCG Blog.

My only worry now is main gear clearance. I designed in 1mm of clearance top and bottom, but I'm wondering now if that'll be enough to allow for chassis flex. I guess I'll only find out when I run it. I can drop from 56 to 54T if need be.

I'm going to be making a final choice on power system this weekend and then ordering it. I'm trying to decide between:

* Neu 1912/1Y, Jazz 55-10-32, 10S 2100
* Neu 1910/1Y, MGM 16024, 8S 3000

The 10S setup would be cheaper I think...

Hey. I found this Jazz modification from a while ago that some heli guys in Germany are doing with their Jazz 55 controllers. This might be the key to avoiding thermals...

Kinda like the old heat sink on a Quark... Just a little more difficult to do.

Anything you can do to pull the heat away from the fets will help.

Hi Aragon,

Good project youve got going here. I'm on the same route as u but I've got nothing to show for the moment.

Regards,
Joe Ling

Thanks Joe. Your HV projects have been an inspiration for me. :)

I have pretty much decided to go with the very out-the-box 10S setup. I'm up for a challenge and saving money! It's about $100 less without that MGM controller...

hmm. don´t think you realy need the mod Ulrich Röhr did to the Jazz55..

imagine: he flies the Jazz55 in his Factor (heli with 1.8m rotordiameger)
with 10s2p Kokam3200 !! (so 6400mAh)
with peaks up to 110A
(so over 3000Watt Power, look here for onboard-diagramm: http://www.ulrich-roehr.de/hubi/e-power18/factor2b.gif)

that are reagions you will not (and want not) reach in a 1:8 buggy

count with around 1000Watt-1200Watt peak max on track
and not more than 2000Watt for speed-runs..

i think you will stay with peaks under the continouse-amp-rating of the JAZZ55 (=55A)

(someone here has an 1:8er with 5s Lipo and 120A peaks running 65mph.. and when you watch the video: thats too fast :D seriously ;) )

oh:
10s 2100mah-Batts..
considering you have 30C peaks
--> that are 60A max (you don´t want more for batterie-life-reasons)

Hey Kraeuterbutter :)

I think you are right. Initially I'll be getting 16T, 20T, and 24T pinions for my conversion. This will allow me to adjust top speed between 30 and 50 MPH depending on desire. I think with 16T for track racing your 1000-1200W prediction will be correct.

2100 cells are the smallest I will use. I chose the 2100s for low weight and their dimensions that should fit my chassis like a glove. I might increase to 3000 or 4000 mAh later.

I think 50 MPH will be the highest speed I attempt. :)

my setup is 5s and 4400mAh batts..

here a diagramm of my power-consumption..
motor-rpm-max is around 30.000rpm
--> speed (calculated from the gear-reduction) should be around 55-60km/h which is already nearly too fast for my driving skills on our relativly small track

http://www.kraeuterbutter.at/Bilder2...e_V_A_temp.jpg

http://www.kraeuterbutter.at/Bilder2...lite_W_rpm.jpg

on that graph i got way too much motor-temperature :013:
was running at hot summer-day without cooling finns or fan on grass
(that has been changed and now no problem)
i use a smaller motor than you will (only 230g weighting Lehner 1930)
so this should be of no problem for you

oh: i use around 2000mAh-2200mah in 10min
more measured datas (also with 4s, 3s and 2s) here:
http://www.kraeuterbutter.at/Bilder2...ono_Messwerte/

instead of increasing capacity on your batts, i would buy another set and change after 15min driving..
its like on helis.. don´t carry too much weight with you ;)

This is very useful information. It is making me wonder if I shouldn't rather get a smaller motor like a Neu 1910 or 1907 to save weight. I have not yet ordered one because Neu don't have stock of the 1912 I requested.

On the other hand, a 1912 might be big enough to not need cooling...

Thank you for posting your data.

I agree with you about batteries, but I've heard there are race segments here that last 30 minutes. It would be a big plus to be able to run non stop for 30 minutes in those races. Talk about nitro spanking. :)

I think I got my spur sorted out. Ended up redrilling it myself and managed to get it mounted more accurately with my $70 drill press. It's now a couple 100th's out instead of a few 10th's! Should mesh ok like this.

Unfortunately the countersink screws can't go more flush than they are. Hardened steel is very difficult to cut.

Assembled the center diff and mounted it all to the chassis. Will be a while still before I get the power system and radio components, but wanted to double check fit. Pics on my Blog.

Hey I was wondering... has anyone considered swapping out some of the steel fastners for aluminium fastners? I think one could save over 100g by swapping to alu. Alot of steel fastners are used for screwing into plastic parts, and in a lot of cases it seems like overkill to use steel there.

That is pretty cool idea.

Long long LONG overdue update on my blog.

:)

damn that's clean.

Looks great. Really looking forward to seeing how it runs.

Only one suggestion, I would look into getting a better pinion gear. That skinny pinion is only touching half of the width of the spur and with that motor on 10s its gonna pack some serious torque. I can see that stripping your spur very easily. And since the spur isn't exactly an off the shelf item it investing $15 in a better pinion might save you allot of hassle.