***__ The 1/8 Onroad Think-tank __***
 

I have had a look at the 1/8 conversions on this site (very impressive). I race electric 1/10 on-road in Australia in a fairly competitive manor. I have a 1/8 Serpent Vector laying around and would like to "electrify" it. I don't want to just go fast, I want to go "head to head" in a race situation against the nitro powered 1/8's. Drivability is going to be critical in this project. Like "BrianG" I would like to try and incorporate the original 2 speed and clutch assembly, my way of thinking is the clutch should slightly smooth out the delivery of power to the wheels whilst also allowing the car to free wheel when backing off. I will use the original disc braking system to slow the car. I realize this has been done before but I don't want to build something that will scare the nitro 1/8 drivers I will face, I want the cars to been relatively even for speed and power.
These are some of my first thoughts, let the ideas flow.

Cheers Andrew

What kind of speeds do the nitro cars reach? You also might want to consult Serum. I believe he did a Serpent car.

Here is a link to the car.
http://www.serpent.com/product/909010/specifications/

In the specs is says 120 Kph+

Just did some rough measuring and it looks as though I'm limited to the 1512 size Neu motors or other brand of equivalent size. I will gather all the relevant gearing information for the car and post them later today.

OK here are the gearing options. Looking for a top speed in second gear of around 120Kph (75mph)

OPTIONAL PINION SIZES
1st gear 15,16,17 I have the 16 installed
2nd gear 18,19,20 I have the 19 installed

OPTIONAL SPUR SIZES
1st gear 47,48,49 I have the 48 installed
2nd gear 44,45,46 I have the 45 installed

The ratio of the drivetrain is 2.27272727 (50 teeth on rear axle and 22 teeth on the transmission shaft)

Tyre diameter
I will be using foam tyres. I expect the average tyre diameter to be around
73mm (2.874 in)


Please feel free to offer advice on anything you may think is of importance.
I am particularly interested in hearing about motor,battery and speed controller options.
After running the particulars through http://www.scriptasylum.com/rc_speed/_top_speed.html
I may need correcting but I see 2 options using the 1512 size motors.

4s LiPo & Neu 1512 1.5 or
5s LiPo & Neu 1512 2d

Again please correct me if I'm not taking certain things into account.
Cheers Andrew

Not sure on how long a runtime you need, but for a efficient, cool running setup that can be geared higher, I would run 6S.

As I have no idea on what is possible, in an ideal situation I would like to be able to run for 15 mins.

I have worked out how much room I have available for the LiPo's it is as follows.
Could I please have peoples input on what brand/size etc. for the LiPo?

H 27 mm
W 50 mm
L 160 mm

squeeforever If run 6s what are my choices as far as speed controls go?

Hi Andrew;

Perhaps you can use the two speed on the track, on the normal road it's useless with the foam tires lacking of grip.

Your sizes might give you some troubles with the right lipo's in 6S;

A speedcontroller that is capable of doing 6S at this moment is the MGM

You could set with 4/5S though, since you don't need the 6S on a ~2.5 kg heavy vehicle

Serum, did you use traction compound on the tires?

Personally, I would go for something like a 6S1P Flightpower pack (no idea if it will fit though) with one of the 6S capable MGM ESCs and a Neu 1512 1.5y/F.


Differential Ratio: 1
Transmission Ratio: 2.2727
Other Ratio: 1
Spur Tooth Count: 45
Pinion Tooth Count: 19
Total Voltage: 23.4
Motor KV: 1900
Tire Diameter (inches): 2.874
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.009
Spur/Pinion Ratio: 2.37 : 1
Total Ratio: 5.38271 : 1
Tire Circumference (inches): 9.03 inches (229.34mm)
Total Motor Speed: 44460 RPM
Vehicle Speed: 70.62 MPH (113.44km/h)
Effective Speed Rate: 3.02mph/V (4.85kmh/V)
Effective KV Value: 1900
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...

Are there any ill effects if I was to wire in series a 3s pack on one side of the car and a 2s pack on the other-side (to try and offset the weight of the motor and to keep my L to R balance even)

What sort of runtime can I roughly expect from a 5000 mAh pack in the combinations suggested. Is there a formula for working this out?

That should work just fine as long as both packs are built from the same lipo cells. People do that all of the time in the emaxx and revo gmaxx setups.

What parts of the car did you use to determine to boundaries of your available space for the battery? When I did my Serpent 835, I made a custom top plate using the original one as a pattern, and placed a cutout in the center area where the gas tank was to let the battery come through. I then stacked A123 cells in a 3s2p configuration (three on bottom and three glued on top like a brick). When you break down the Dewalt packs to get the cells, the paper cylinder outers on them are very good for gluing using basic wood glue. I would guess that with the extra length of the 8th, you could probably go 4s2p.

since the room is tight; can anyone explain me the reason why using 6S on a ~2.4kg heavy vehicle?

Only reason I would use a 6S setup would be shear power in combination with high efficiency. With the high speeds needed, your gonna need alot of power. 6S setup will yeild more power as far as the batteries go.

I was using the available space under the top plate, extending out toward the body. Do you have a photo of your 835 with the cells in it?

I just want to reiterate that I need to be able to RACE continuously for 15 mins (10 mins. minimum) I'm not interested in just doing speed runs.

I have also found out that a high performance nitro engine out of a 1/8 can produce nearly 3HP. Is 2237.0996 Watts out of the question? Of course this would not be continuous.

I had considered that when making my suggestion of the A123s. The first thing you need to address would be the power output match of a typical 8th in the small space that you are afforded for your conversion. I was looking around at the various batteries currently out, with your dimensions in mind, and nothing to meet your needs exists. The only hope you have would seem to be something you can quick change, akin to a fuel stop for a typical 8th. I don't really have accurate figures to go from, but it would seem that battery sizes (physically), are about 1 to 1 in runtime with the size of a gas tank when power output is that high. A typical 8th doesn't run that long without needing to be refilled, but I'd bet that if the tank was as large as a 6s high capacity battery, it could run that long.

I have since changed the car over to 5s1p, but you can imagine what I was talking about. Sorry about the cell phone pics.

Sorry myndseye, I made an error in my measurement of available battery space. It should of read like this.

H 27 mm
W 100 mm
L 160 mm

This is the available space under the radio tray. I still haven't decided where to locate the batteries. I'm also thinking if I use 3 seperate 2s1p 5000 mAh packs to get my 6s I can also use these packs individually for racing my 1/10 on-road. Mounting 3 seperate packs on the car wont be fun but at-least I will still be able to use the packs after the nitro 1/8 drivers ban me from racing, because I'm overtaking them down the straights.:lol:

myndseye, What speed control are you using?

Anyone out there that can comment on the MGM Compro 160 amp speed controls? My biggest fear is that I end up with a car that is undriveable because the throttle is like an on/off switch.

I was running a Mamba Max on this one. The two white strips behind the battery are double sided tape where the speed control goes.

Slightly off topic but here are a couple of photos of my 1/10 car.

These are about the most versatile lipos other than the A123s. With some creative wiring, you may be able to come up with something useful.

http://www.maxamps.com/Lipo-5500-74-Saddle.htm

I did have a look at those but I think the thickness is going to be the issue "34mm X 66mm X 31mm" just a little to thick.
I think I'm just going to work out a way to get 3 seperate 2s 5000 packs mounted on this thing (even if it does look untidy).

I think you should be ok for 15 minutes if you use the 5000mah Flightpowers.

I would run 4s on a 1/8th onroad, these cars RTR can weigh less than the wheels and tires on some MTs. If you could fit 4s2p or 4s3p of smaller packs that may be ideal

Here is the best layout I can come up with with 3 separate 2s packs (Dummy packs are 10mm longer than actual packs). I think this would keep the left to right balance fairly close. The dummy motor appears to fit perfectly. I'm having a friend machine up the pinion carrier which as you can see will have to be extra long. The electronics (receiver,speed control and brake servo) will be mounted on the top plate.
I would really like to mount the motor using some sort of "band clamp" type mount. So far I haven't found anything any link/suggestions?

Uhm, why don't you use 2 3s1p maxamps 5Ah lipos?
http://www.maxamps.com/Lipo-5000-111-Pack.htm
They are 45mm X 138mm X 26mm so no need for 3 separate packs, only two...

Bye:mdr:

I race 1/10 electric on-road usually and the 2s packs are the only ones I can use under the current rules. So if I use 3 x 2s packs I can use them in my 1/10 and 1/8 (just better bang for my buck). Looks like I'm going to run these. http://www.trakpower.com/

I now have a good idea of the hardware I need. Now I need to look at chargers and balancers. I have one of these already (only good for 4s I believe) http://www.robitronic.eu/elements/ap...erloader_e.pdf
1. What is going to be my best option for charging 3 separate "Trakpower" 2s packs at the same time?

2. I would like to get a balancer at the same time.

Recommendations please

Cheers Andrew

OK, I have been given a better donor car than the old Vector. I now have a Serpent 950R, not a huge deal of difference but it is more refined and a little more current.

I want to get started on my custom motor mount but I need to know the exact outside diameter of a NEU1512 motor (1.5y to be specific) but I will take any information I can get (I know the NEU website says 40mm but would like to see if there are any slight tolerances). I would measure my own but I don't have it yet I'm still waiting for Mike to reply to an email.

If you have a 1512 could you please measure the outside diameter and post or pm your results (.00mm resolution would be nice). I'm interested to know if there are any lips where the end plates are as I'm making a band type clamp and this will effect how well it will hold the motor.

I'm catching up with a guy this weekend who has a vacume former and works with CF. We are working on a CF battery tray and side intrusion protection for the packs. I have attached a couple of pics of his work, all custom made by him, it's very nice.

The charger in your link is good for up to 4s. Are you wanting to charge all three packs in series, or seperately? If in series, a single 6s capable charger and a balancer like the LBA10 will work fine. You'll just have to make a special type of Y charge and balance adaptor.

Sorry, can't help on the 1512 dimensions...

You mean like this Brian? :wink:

Progress is going well. I have made up some temporary battery trays (I'm going to make the permanent ones from CF) from 3mm alloy, I'm going to take to them with a drill to reduce some weight this weekend. I have attached a pic with the tray and my fake batteries (my 3 X NEU 2S1C 5000 mAh are in the mail) as you can see it looks like the L/R weights should be close. I will know more when the packs arrive.

I have also attached a pic (far left) of my temporary motor mount system (it hasn't been line bored or machined for weight reduction) it is a simple band clamp setup for testing only, the permanent one which I have nearly finished deigning will be CNC'd and include a integrated 12 fin heatsink and will still be a band type clamp. It will use the original 21 size motor mount bolt holes as well. A friend is going to transfer my hard copy to CAD so if anyone in the industry knows what format I need to give the machining shop please let me know.

Still waiting on the motor (NEU 1512 1.5y/s) to become available from Mike's shop so I can order the speed control and motor at the same time. Hopefully they arrive soon so I can get this thing up and running.

If any one has a NEU 1512 1.5y (smooth can) they want to sell please PM me. I will consider a finned can but would prefer smooth as I would have to machine off the fins to have it fit.

I would also consider other NEU 1512 motors around the 2000KV range.

Please help as I'm having extraordinary issues trying to get my hands on one of these motors. I even called NEU directly and they are out of stock and expect there to be a six week delay minimum before they have them back in stock.

Cheers Andrew

Just took delivery of my NEU 1512 2.5/D, MGM 16018, 2 speed pinion adapter (thanks Mike) and a few other bits and pieces. I will post some more pics soon, hopfully have it running in some form by the weekend. :party:

Nice setup. I went racing on the weekend and was surprised at how well my brushless mini-t could keep up against the 1/10th scale tourers. They were flogging me due to my inability to keep it pointed in the right direction but it wasn't that much slower then them when I did keep it on the track. It was great fun though. I'm keen to go road racing again now.

I can't believe it. I just received my MGM 16018 speed control and I'm having trouble programming the basic transmitter setup. I have a Futaba 3PK radio and use a Futaba R203HF HRS receiver.

I have tried all the suggestions I can find and still nothing. I can report that when in HRS mode the motor will continuous beep...beep...beep etc after holding full throttle and the switching on the speed control. I have tried reversing the channel but still get the same response.
When I switch to either PPM or PCM mode I get no recognition from the speed control or motor. I have tried reversing the throttle channel in all modes and still nothing. I have even tried to on hold the throttle on just slightly to see if it makes a difference and nothing happens, no beeps, nothing.... :neutral:
Maybe I should find a standard (non HRS) receiver and try it. (wish there was a crying smiley)

Just tried my old JR XR3 radio and it programmed it fine. Might send this one back to MGM and have them install the latest firmware. Another set back urrrgghhh. :cry:

Gave my car a shakedown run today. Very promising results. I will post pics and maybe a vid over the next few days. I should also have some data from the eagle tree data logger for viewing also.

Got a small vid of it's second shakedown run.
<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/gGlx5_-r1rU"> </param> <embed src="http://www.youtube.com/v/gGlx5_-r1rU" type="application/x-shockwave-flash" width="425" height="350"> </embed> </object>

Sorry about the audio I think the tape was bad.

man that thing has some spunk.