Tom
Member
- Messages
- 8
- Location
- Farmington Hills, MI
Too expensive? Too little runtime? Maybe even too hi tech? There is a cure for all this but it adds a lot of weight. To start out we all give our vehicles a beating the stock version can't take. So what do we do? We replace the stock parts with aftermarket parts that can take the type of abuse we dish out. If it won't go fast enough the only cure is a more powerful engine, right? Wrong! With a more powerful engine you must use deep gearing to get any decent acceleration at all and then if you're using more than one speed each of them must provide a ratio that lets the engine move the vehicle faster. Sound familar? Now, what would we do if we had tons of bottom end and less top end all at a lower engine speed? How about shallow gearing to get us off the line in a hury and then if you have mode than one speed gear up from there? What would it be like if we did that with a flat torque curve? Horsepower equals torque multiplied by rpm divided by 5252. With a high horsepower engine or motor you absolutely must have high torque at the horsepower peak there's no way around it. So you've got a choice there: an engine/motor with no bottom end and everything at the top end or an engine/motoe with no top end and everything at the bottom end. The first of the two perfectly describes a two-stroke - run at top end all the time and blow your engine. I've had lots of experience with that racing motorcycles. The second of the two perfectly describes an electric motor - and to a lesser extent a four - stroke engine. There are far less expensive motors than Lehner - Lehner blow easily if you push them too hard - that don't develop peak horsepower at 40,000RPM and have no bottom end at all but are just the opposite - peak torque at low RPM, a flat torque curve and peak horsepower at 3,600 RPM all without lipos. Talking pure horsepower without any load on the motor it takes three of these to equal one top-of-the-line Series 3080 Lehner. Talking pure torque, it takes one of these to equal an unlimited number of series 3080 Lehner's. Two-strokes are like the Lehner's I mentioned. If you want top end buy a bunch of them because you'll always have at least one being rebuilt. Sounds like more bottom end than a Large Scale can take? Go back to the part about aftermarket parts. Need really strong gears trry CAT5. Need belt drive instead? Check out the accessory drive belt on your car's engine or the final drive on a Harley. When was the last time you saw a high horsepower low torque Harley? When was the last time you saw a car with an accessory drive belt more than (roughly) three inches wide? These belts come in other widths too. Now, to address the weight problem. This one will sound like a real pain not to mention an impossibility. Read on and find out how to make the impossible possible. The motor I've been referring to weighs many times as much as a Series 3080 Lehner, is a torque monster and only puts out about three times as much horsepower as the wimpy little unmodified two-strokes most Large Scale's come with. The battery if you use the stock one weighs tons - much more than a tankful of gas. I'll address the battery first. This battery is a super low-tech battery and there are higher tech with equal or greater out put and less weight - sometimes far less weight. None of these are LiPo's. All of them have a high Amp hour rating. Now for the motor. First I've got to say that if you use one of these mount it as low in the chassis as possible to keep the center of gravity and the center of mass low. This motor can be mounted in any position so if you want to use a trick primary drive you can mount it with the shaft vertical and lower it even more. OK, now for the worse part. This motor weighs between 20 and 30 pounds. That's the worst part. Next, depending on which model you get it has either 5 or 6 horsepower. Sucks? Sure does so far but there's more. Tons of bottom end and it lasts forever. Still sucks, right? Well, so far it does. Now to identify the motor. Are any of you Golfers? (GOLFERS?. Have you ever used an electric golf cart? If you have you're part way there. How about those of you who've taken the transportation at a hospital that looks like a stretched golf cart? You're part way there. In most cases the motor that powers both is a Briggs & Stratton Etek. Tons of torque - hey, they can haul a bunch of people to their cars all in one run. Horsepower? You golfers know that golf cart isn't equal to a AA Fueler but it will take it's occupants anywhere on the course except through the sand traps if you ignore that dumb little strip of pavement they're supposed to stay on. And have you ever seen a light golf cart? If this sounds like too much to do with a production vehicle, consider building one from the ground up an easy and cheap way such as suspension and running gear from a four wheel drive ATV and you might as well take the wheels and tires too. This stuff is cheap used. A chassis plate or frame made from new metal (try onlinemetals.com if you don't want to order in bulk). ROBOT SERVOS because you'll need real power to turn it. OK. Industrial servos work too. Your motor(s) motor electronics and batteries and your R/C electronics. To build a MT you might put one motor in front to drive the front wheels and one in back wheels with everything else between them. That would spread the weight out evenly. You will need one 300 Amp speed controller per motor. Yeah, 300 Amps. And you can power the motors with up to 72 Volts each. Feeding them 72 Volts instead of the common 48 Volts eliminates your top end shortage while increasing the bottom end. You can pull wheelies anywhere with one motor fed 48 Volts just imagine what you can do with two of them fed 72 Volts!
arty-time:arty-time:
arty-time:arty-time:
