Original Kyosho Ultima and Hot Batteries
 

Got a question for anybody that has dealt with the "old" cars. I dug out my Kyosho Ultima (yep, built in the 80's), pulled it apart and rebuilt it using new shock oil, diff grease, etc. I installed a Speedworks Super Speedway Stock Motor (made by Trinity) that I had from "way back when". The thing runs great, but the new NiMH packs I'm using get incredibly hot when running them, and they only last a fraction of the length of time that my buddy gets with the same packs. He is running a RC10B4.2 with DTX 3900 motor brushless setup. I can keep up with him while the batteries are fresh, but they just don't last long.

Is this the difference between the "old" brushed technology and the new brushless, or is there something else going on?

I am using a Futaba MC111B controller in my Kyosho. Should I just suck it up and get a new motor and esc?

I am also seriously considering getting a used RC10B4.2 or Kyosho RB5 and outfitting it with new electronics. Would this be an even better idea?

Any help and/or advice would be appreciated.

NCDaveD

Honestly I would shelve the ultima and get a newer ride. Brushless motors and escs are alot more efficient and reliable. Plus no more motor rebuilds!

A newer platform will have parts support where the ultima might be in a bind if you break something.

Also, even if you get a new motor and esc (brushless I assume?) there is no guarantee that the Ultima's transmission can handle the torque and the speed.

I'd leave all that old school gear in the Ultima, clean it up really well, and shelve it.

Get a nice used B4.1 or 2 (pretty cheap these days) and get a modern electronics setup and have fun!

If you are running tamiya molex plug you might be getting high resistance in the leads leading to a hot battery. Brushed motors are also horribly inefficient and waste alot of power to heat especially if they are not maintained and comms kept true.

My opinion would be to get a newer car and go brushless, as they will be easier to get parts and will hold up better to brushless.

The old ultima is a great car and parts are available on ebay still but the gears are all plastic and not very stout to hold up to brushless power. If you are running a MK1 with the aluminum chassis they are also extremely vunerable to front end damage.

There are a couple things going on. First as you've pointed out, the brushless motors of today are much more efficient than the old brushed motors. Over 90% vs in the 60's so basically a brushless motor is a 50% efficiency improvement. That alone will increase runtimes. Lipo batteries are also much more energy dense than nimh batteries and will last longer as well. If you have any inefficiencies, they will be seen in the form of heat.

The Ultima had 32 pitch gears which would have no issues with modern brushless motors. My concern would be your differential. That car has a gear diff unless you upgraded it to a ball. The original gear diff has only two planetary gears and they are a very soft pot metal such as pewter. These might not last long.

If you still have the original metal ladder style chassis where the battery sits across and out each side, I'd be concerned with battery terminal safety with a lipo battery. I'd be afraid of ripping one out if it got snagged on something. A graphite chassis such as on the later Ultima cars would definitely be better.

While these are concerns, I see no reason not to run the car. I love running vintage cars. Too many people today think old means junk or something that should be relegated to a museum somewhere. That's just not true. Have fun with it. Just understand it's limitations and any difficulties getting spare parts.

In order. Oh yea, more than you can imagine. Something else ? yea lipo batteries and 2.4 radios, it's like going from black and white TV to color. I'm an rb5 guy but you can't go wrong with the ae. Yea, if you want to get back into it ya gotta step up. Welcome back.

First and foremost I want to say "Thank You!" to everybody that responded. I REALLY appreciate you all taking the time to help get me educated.

To give a little more info.....yes, it has the original gear diff. and aluminum ladder chassis. I did upgrade it originally to the gold shocks, new shock mounts, etc. The Tamiya plugs were cut off and Anderson Power Poles installed as soon as they were available. There is a TON of extra parts in my "misc." box, so I can keep it going awhile.

I think I'll pull off the Trinity motor and install the old one as that was when the problems really started. I'll keep my eyes on the "for sale" area (I have seen quite a few good deals in there) and get a good used buggy with "almost new" electronics. The Ultima will be there whenever I get an "itch" to run it.

It will be nice not to have to put 8 AA batteries in my transmitter :).

The buddy I mentioned before is an AE fellow and built a gold pan RC10 when I built my Ultima. We ran against each other for years. His RC10 did not survive the many moves over the years which is why he built an RC10B4.2 last year when I pulled out my Ultima. I just need to make sure he doesn't run away from me in the future.;)

Thanks again everybody!
NCDaveD