ryan_t888

It may be difficult updating all the build threads on the forums, however the main one will be located here if this one falls behind:

[link=http://www.radiocontrolinfo.com/forum/viewtopic.php?f=17&t=17]DM1 Brushless Conversion[/link]

The build will hopefully progress at a fairly quick rate.

1/8th scale electrics are quite rare still. I would have thought by now, the market for them would have grown. Larger models have grown on me in only the last couple of years. In general, they handle tougher conditions and the fact I'm limiting my builds to multiples of 4s LiPo from now on.

All details will be kept in the main thread above and I will do my best to update the others.

Here's what I have to work with, now let's get the ball rolling.




Ryan

Foxy

Seen some absolutely mental brushless Inferno GTs on 6s.

4s won't be that special, why don't you do something like 2350 6s? What you planning on actually doing with it? Rally? On road? Bit of both? Speed runs?

I have plans for a future 5S 1/8th on roader parking lot basher, possibly Thunder Tiger EB4 based (the on road version), dunno what motor yet, may use it as an excuse to try out some of the cheaper 1/8th motors and ESCs, like Tacon and HK etc.

ryan_t888

The only goal for this build is to achieve 100km/h or 62mph. That's all. It will never be run competitively.

Why not 6s?
This is a good question and probably many are wondering the same thing.
I have a slew of 4s LiPo's. I focus my builds all around 4s LiPo's. This is for the Planes, Cars, and Boats. My main focus is boats where the 4s idea works very well.

I tried getting graph data for the castle on 4s since I was planning on another motor setup. However, no one had it available, so I decided to move forward with it and make some graphs of my own.

My original plan was to use the 1521 1D I have or try a 1521 0.5Y using the new Castle Ice ESC. This setup would be fairly competitive against 6s setups with the same gearing to match RPM's.

The 1521 currently in use in a boat will pull 150A continuous on a 240A continuous ESC for 2.5 minutes or so. 4s2p - 11 600mAh are used. It is done this way to meet specific restrictions by voltage.

So I'm stuck with 4s or 8s essentially. Maybe I'll build another one for straight line speed only, for the type of performance everyone loves to see. This would be fun.

Ryan

Foxy

You will easily manage 62mph on foam tires with a 4s 2200kv setup and the right gearing, without the electronics even breaking a sweat. Good luck

ryan_t888

Thanks. I'm going with the 1512 1Y. 2650kv to better suit the gearing options available.

Ryan

yakfish

My Feedback: (27)

I will have to keep an eye on your progress. I am getting ready to do a similar conversion with my Inferno GT. But I will be going for max speed.

Foxy

I think the 2200 on a bigger pinion will get you there more efficiently than a 2650 on a smaller one. The 2650 is intended for those who want to go quite a bit faster than 62mph I reckon. If you went 2200 you would also have option of ultimately going 5s or 6s if you ever did feel like it. With the 2650 you are all but precluding that option (2650 will have downtime on 6s while you wait for it to cool, 2200 will not). I'm no motor expert, but I've been reading heavily about these 1/8th speed cars, and most use lower kv motors and bigger gearing.

ozzie-crawl

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ryan_t888

Most of the details will be in the original build thread linked in post 1. I will try to keep the other build threads on the other sites up to date as best as I can. Nearly all the items needed, I already have ready for assembly.


My options are 4s or 8s.

Both the 1512 2650kv motor and the 1515 2200kv motor are 1Y winds. However the 1515 is physically larger by some value. This allows the motor to dissipate more waste heat. However even though they are both "Y" wound motors, the larger motor will have a higher resistance. Thus the extra mass of the motor will have to dissipate the extra heat caused by the increased resistance.

In other words if the 1515 2200kv motor was running at 80A and the 1512 2650kv motor was running at 80A, the higher resistance of the 1515 motor result in more waste heat but the larger can will be able to better dissipate the waste heat. Essentially a 4s comparison would show both motor should be competitive. If 6s was used, the 2200 would work much better. I personally would not recommend that much power through a 1512 sized can. Not enough mass to remove the heat.

In addition I do not believe they make gearing available to push a 2200 up to 100km/h. I will be using the 2 speed tranny with 2 speed pinion as listed in the main build thread. According to some numbers I've worked out, I'm already near the highest gearing available for spur and pinion and I'm just around 100km/h. 2200kv would put me out of range.

I'll throw some numbers at you as a prediction. The 1512 2650kv motor on the way to 100km/h will most likely pull just over 100A during acceleration. I doubt I will see bursts in excess of 115A. I'd imagine at top speed it will be drawing around 90A or so. I do not believe I will have any motor heat issues regardless of what I am doing. None of the motors I've owned have ever exceeded 140F. And this one will not either.

I understand many conversions are out there. I've been watching the DM1 cars ever since they came out. Up to this day I still can not name for you a Brushless 1/8th scale RTR pure on road car available. Everyone has to throw lots of money at the nitro chassis to convert them. Converting is fun, however there's many more out there that would still prefer RTR.

Ryan

ryan_t888

Made OK progress.

Stripped down all nitro components from chassis such as servo mounts, engine mounts, any anything else that must be removed.



Removed Front End Assembly and Mounted to New Chassis



Rear End Assembly Mounted



Battery Tray Mocked up and Secured



Motor Mount inserted



Brake Servo is Mocked up just needs to be secured. Will get that sorted out tomorrow.

Ryan

ryan_t888

Servos Mounted




Looking at the stock brake disc, it's made of the typical fibreglass material. I'm thinking in less than 5 passes I will be able to smoke this one up pretty good. The build will be heavier requiring more energy absorbtion to stop from higher speed.

I do not have this part yet. What option would be best for brakes? I'm currently looking at steel discs, with the steel pad and what they refer to as washers. (the washer is the actual frictional pad)

Ryan

Foxy

This is something that I am toying with on my Tekno conversion of my MBXT... I still haven't decided if I am going to retain the mechanical brake at all. It's certainly not necessary. I will try without the brake first and only reinstall it if I really think it's necessary (and I don't expect I will).

ryan_t888

I guess that conversion of yours doesn't use a clutch?

I decided to go ahead with a clutch and 2 speed since it may be a bit easier on the system at lower speeds and I actually love the idea.
It's a spur/pinion ratio difference of 2.2 vs 3.0.

Need to get some brakes as I know the glass disc will melt in the first 5 minutes.

Ryan

Foxy

It does include a clutch, which similarly, I will not be using. I think for your intended purpose, you are making a mistake using the clutch and brake. You will not have ANY shortage of acceleration, so the 2 speed is totally unnecessary as well. Go straight to the FD of the 2nd gear, you will also shed a lot of weight using no brake servo, shed a lot of rotating mass getting rid of clutch bell clutch shoes, brake, 2 speed. I also think the first thing to break will be your 2 speed, probably the first time you run it. Go ahead and try with clutch and mech brake, but I'd bet my bottom dollar you have gotten rid of it after only a few outings. Why introduce so many additional points of failure which aren't even needed? Even the racing community is split on the value of using a clutch and brake for racing, let alone parking lot bashing.

ryan_t888

I agree with you, it's another point of possible failure, I don't really need the extra gear ratio / smaller pinion it offers, and most importantly a lot of weight can be saved. Somewhere around 6oz or 165g.

It took me a while to determine which way to go in the planning stages as I like the simplicty however I also like the idea of mechanical brakes and 2 speed.

However, I'm going to give the 2 speed a try since I already have the kit to do so which makes installation a snap. The 2nd gear clutch is massive and I do not see it failing for a long while. I know the glass brake disc will be cooked in the first run. Still trying to sort out that. IT should be the last part I need.

Ryan

ryan_t888

Popped open the Ipanema Slicks. They look pretty decent.



The clutch was setup. The springs from the kit were used. These springs are quite light and should grab at low RPM which really doesn't matter that much for electric. What I like about it is, they will have more bite at higher RPM's since they are engaged earlier.





Lastly, Finished up the Body. Nothing special here. To me it's just a completed step. Don't know why I decided to snap the photos before mounting the wing. However the wing matches the main body colour pattern.

ozzie-crawl

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ryan_t888

That's another reason I prefer the 2 speed. It will greatly reduce load at low speeds.

Although Brake distribution would be very nice, the DM1 center shaft with the 2 speed assembly is solid.

Ryan

ryan_t888

It Moves!

Ended up getting enough done to see if it fires up.

The ESC and Motor were first pulled from the box.



The Motor, now a bit dusty was mounted and the clutch secured.



The ESC, also now dirty was mounted in the radio tray area with strong Velcro. The receiver was also mounted using the stronger velcro.



I took it in to the back yard for a quick little spin on pavement. Make certain brakes work, ESC arms, trims are set. It worked well. Just need to sort out a couple things prior to its first actual outing.

Should be able to get some road time within the next day or so.

ryan_t888

Went for the first run.

I should have put the slicks on right away. Didn't realize they wouldn't hold up for the weak 71km/h that showed up on the GPS.

Managed to flip the car nearly right away. Not even sure how this happened. Pretty neat to watch an 1/8th scale on it's roof for 50 feet.

The stock rubber were ballooning quite a bit. Decided to take it easy as I forgot to bring the slicks with me. This explains the 71km/h.(44mph)

It only took 5 or 6 passes until the brake disc let out so much smoke, it looked nearly like electronic failure. Unfortuneately I can't source anyone who has upgrade brakes in stock. May need to order in.

Just as I was about to quit, the rear tire completely blew out on me. Slicks are installed and ready to go.

I hope for the next outing I can get some video. Acceleration seems great, top speed is still in question.

Foxy

You're only gonna destroy those slicks too. You need these...

http://www.amainhobbies.com/product_...-Dot-17mm-Hard

ryan_t888

Why would I destroy the Ipanema 1/8 GT Streetable Belted Slicks?

Ryan

Foxy

Because no rubber tires last long on fast brushless setups, and foams are better all around anyway.

ryan_t888

I've been told to stay away from foams as they would be chewed up in three runs.

Ryan

ozzie-crawl

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