Fastest Motor on 6s?

[TexasSP]

Putting that motor in a revo is impractical for many reasons including the shear size. You also can't compare a flat chassis truggy to the revo chassis when doing something of this nature.

A motor that size is also not needed to reach 100 in an e-revo. Many of the options already suggested would be a good start. Either way it's something that will take some experimentation to get right and more than just the motor mount and size needs to be in the equation.

RootzMan, we all know that much of what is on here is a matter of opinion so no need beating the subject to prove whatever point or feeling you have about it. You do have to keep in mind that most of the people here are offering their opinions based on personal experience and facts which goes much further than just someone stating their opinion who has never tried any of this before.

[RootzMan]

Originally Posted by TexasSP

Putting that motor in a revo is impractical for many reasons including the shear size. You also can't compare a flat chassis truggy to the revo chassis when doing something of this nature.

A motor that size is also not needed to reach 100 in an e-revo. Many of the options already suggested would be a good start. Either way it's something that will take some experimentation to get right and more than just the motor mount and size needs to be in the equation.

RootzMan, we all know that much of what is on here is a matter of opinion so no need beating the subject to prove whatever point or feeling you have about it. You do have to keep in mind that most of the people here are offering their opinions based on personal experience and facts which goes much further than just someone stating their opinion who has never tried any of this before.

Thanks for chiming in TexasSP. Not that it's my thread but anyway...A couple of points:

1) Don't recall anyone saying anything about a truggy

2) If it were that easy to get an E-Revo up to 100mph, I'm pretty sure that somebody would have done it already. To my knowledge, no body has. I have spent a great deal of time and money trying and not succeeded. Have you?

3) The only point that I was making is that I believe people should not call each other stupid and that they should not state their opinions as fact. For sure, many of our forum brethren state their opinions as fact. If you feel the need to defend them then quite frankly I think you are promoting narrow-mindedness and dogma whereas, I would imagine that forums exist to further understanding, rather than limit it. Surely, if some body has an opinion that they can back up with experience, their opinion would be all the more credible if they were to share their experience.

4) I have some knowledge of the achievements of our fellow contributor X-Y and, I can tell you that there is no doubt in my mind that he knows far more about speed racing electric RC's in general than all but a handful of people Worldwide. His English may not be great but his engineering is.

Now, I propose we return to the subject at hand; The not inconsiderable matter of propelling Kevlar's Revo to 100mph and above.

So, Kev. Any progress?

Originally Posted by TexasSP

Putting that motor in a revo is impractical for many reasons including the shear size. You also can't compare a flat chassis truggy to the revo chassis when doing something of this nature.

A motor that size is also not needed to reach 100 in an e-revo. Many of the options already suggested would be a good start. Either way it's something that will take some experimentation to get right and more than just the motor mount and size needs to be in the equation.

RootzMan, we all know that much of what is on here is a matter of opinion so no need beating the subject to prove whatever point or feeling you have about it. You do have to keep in mind that most of the people here are offering their opinions based on personal experience and facts which goes much further than just someone stating their opinion who has never tried any of this before.

Greeaaaatttt day darn good info!dido.

[BrianG]

It seems that most attempts at very high speeds boil down to "throw more power at it". Sure, you can make a brick fly with enough power. But someone should come up with a better way to utilize the power we already have. Gearing up high enough to achieve 100mph+ speeds is hard on the ESC, and you still have to wind that motor out. Two-speed transmissions aren't great because of that torque change at the shift point (tried it - didn't like it). Too bad someone couldn't come up with a reliable, lightweight, and relatively inexpensive CVT setup; would provide better off the line control and power, yet keep the acceleration smooth and motor in its ideal "power band" to take full advantage of a motor's capabilities without stressing everything so much.

[RootzMan]

Certainly, when it comes to a brick like the E-Revo, I can't think of a whole lot that can (practically) be done to reduce the requirement for significant levels of power output.

Above around 70mph, aerodynamics starts to play its part and, if one is contesting an open-wheel record, one is forced to make a trade-off between grip and drag. The wider the tyres, the more grip you'll have but the more drag they'll cause. Worth pointing out that speed racing is essentially drag racing by another name and over a longer distance, since we are limited by eyesight and radio control range. Of course, there is the option of an FPV camera system but, as far as I'm aware, no body has successfully implemented such a system on a speed run car.

So, we're back to drag racing over some 700 or so feet which is already beyond the limit of eyesight. One thing that is rarely realised is that, at some point, drag will probably take over. The amount of drag holding the vehicle back with become close to the mechanical grip pushing it forwards and the nett result will be that, no matter how much power you have, your tyres will start to lose their grip. It's just like holding the vehicle against a wall except you're already going fast and it's very easy to lose control.

There are designs for small, light-weight CVT's but, so far as I'm aware, nobody makes one small enough to use (yet!). One area for development is electronic traction control, which I'm currently working on. It's not as easy as it may seem and besides, when the drag takes over, traction control would simply prevent the vehicle from accelerating. It would only be useful in an ultra-low-drag vehicle.

Below 70mph, the best thing you can do is reduce weight as much as possible, while increasing power and strength. This will increase acceleration but take it from me, the faster you go, the more likely you are to lose control. And the more damage will be done when you do. Unless you have an unlimited budget, there's another trade-off between weight and durability.

For the record, my solutions to these problems were:

1) Reduce aerodynamic drag: Built a Revo-based body shell which extended down to a splitter close to the ground and was trimmed to minimise the amount of air negotiating the suspension arms. Also reduced frontal area by narrowing the track using Slayer arms.

2) Grip: Produced a set of foam tyre/wheel combo's. Also used specially reinforced HPI Phaltline tyres on Blast wheels. In the end, the foams were best at the rear and the Phaltlines at the front.

My avatar gives you an idea of the end result.

I think that the "best way to utilise the power we already have" is exemplified by Tim Smith's JC Dragworx dragster which has managed 179mph in practice on 6S, although, at a recent speed run meeting, Tim "only" managed 143mph with no front tyres! This car has also managed to achieve 119mph on 2S. It's very light. Very streamlined and has loads of grip. Power is probably somewhere around 2.5-3KW. Here's a pic...

[snellemin]

The way I see it is this.

Big 2 pole and 4 pole motors will be maxed out at 50-60k rpm. So you pick your kv poison based on your available voltage. Keep the weight down and you will need less torque, which translates to less needed amperage. So a smaller/shorter motor can work.

Use thick wiring and good connectors. Keep the wires as short as possible, but enough to flex a bit.

Based off my experience in my smaller cars, I would say a 1515 is too small of a motor to turn those big tires at 60k motor rpm, for record breaking speeds. I would stay with a motor in the same diameter, but choose a longer can version like a 1518, or 1521 to gain the torque to turn a bigger gear.

[RootzMan]

Originally Posted by snellemin

The way I see it is this.

Big 2 pole and 4 pole motors will be maxed out at 50-60k rpm. So you pick your kv poison based on your available voltage. Keep the weight down and you will need less torque, which translates to less needed amperage. So a smaller/shorter motor can work.

Use thick wiring and good connectors. Keep the wires as short as possible, but enough to flex a bit.

Based off my experience in my smaller cars, I would say a 1515 is too small of a motor to turn those big tires at 60k motor rpm, for record breaking speeds. I would stay with a motor in the same diameter, but choose a longer can version like a 1518, or 1521 to gain the torque to turn a bigger gear.

Makes a load of sense snellemin. Course, I would say that as I'd already suggested a Neu 1521.

Mind you, I'm moving toward sensored at the moment, so the next motor destined for my E-Revo will be a Novak Ballistic 8L - When they finally release it!

Now I've just gotta choose between an RX8, an LRP iX8 and Novak's new Kinetic 8. depends how patient I can be!

[TexasSP]

Your right rootz, you have the only opinion and experience that matters. Have fun with that.

If it where me, I would follow snellemin's advice and also use a smaller wheel/tire combo. I would probably make my own tires and put them on short course wheels. Hitting that speed will take an immense amount of custom work not matter what. Personally, I would pay close attention to the land speed record holders body styles and how they setup their vehicles.

[RootzMan]

Originally Posted by TexasSP

Your right rootz, you have the only opinion and experience that matters. Have fun with that.

If it where me, I would follow snellemin's advice and also use a smaller wheel/tire combo. I would probably make my own tires and put them on short course wheels. Hitting that speed will take an immense amount of custom work not matter what. Personally, I would pay close attention to the land speed record holders body styles and how they setup their vehicles.

I have no idea how you get the impression that I think my experience matters more than any other. I can only imagine that you didn't read my posts correctly. I think no such thing and am always prepared to learn from people who's open minds and creative character have allowed them to explore new ground.

Correct me if I'm wrong but it seems to me that snellemin's only post in this thread concerns motor choice and nothing about wheels or tyres. I find that a useful maxim is always to read 3 times before typing.

Strange how you now state that hitting 100mph will take immense effort when your previous post implied that it was easy. And if you think it's easy to make tyres, I suggest you do so. You may find it harder than you think.

Your suggestion that short-course-based wheels would be suitable as a basis for a speed-run wheel is very interesting, if somewhat misguided. I'm not sure why you chose short course. I tried buggy wheels with on-road tyres ( inconclusively )...



However, I'm not convinced short-course wheels would be an improvement. Unless you have a persuasive argument.

[TexasSP]

Originally Posted by RootzMan

I have no idea how you get the impression that I think my experience matters more than any other. I can only imagine that you didn't read my posts correctly. I think no such thing and am always prepared to learn from people who's open minds and creative character have allowed them to explore new ground.

Correct me if I'm wrong but it seems to me that snellemin's only post in this thread concerns motor choice and nothing about wheels or tyres. I find that a useful maxim is always to read 3 times before typing.

Strange how you now state that hitting 100mph will take immense effort when your previous post implied that it was easy. And if you think it's easy to make tyres, I suggest you do so. You may find it harder than you think.

Your suggestion that short-course-based wheels would be suitable as a basis for a speed-run wheel is very interesting, if somewhat misguided. I'm not sure why you chose short course. I tried buggy wheels with on-road tyres ( inconclusively )...

However, I'm not convinced short-course wheels would be an improvement. Unless you have a persuasive argument.

You make a lot of assumptions again and again.

I have made my own tires, it is done quite a bit in the crawler/scaler world using other tires, cutting, then gluing.

Bigger tires make for more weight and higher rotating mass, thus robbing you of energy that could be put elsewhere.

Like I said, I did the speed thing, I know what it takes. I never implied it would be easy. I can tell you though that I never got anywhere using bigger tires and gearing for them.

As for snellemin's posts I was agreeing on the points about motors and then adding my own about the tires. You seem to want to pick apart little things too much. Stop being so asinine about the whole thing.

[RootzMan]

Originally Posted by TexasSP

You make a lot of assumptions again and again.

What assumptions? Assuming you don't know what you're talking about? I would have said that was self-evident.

Originally Posted by TexasSP

I have made my own tires, it is done quite a bit in the crawler/scaler world using other tires, cutting, then gluing.

When the vehicle in question is only going to do 3mph, cut'n'shut tyres are all well and good. I would never recommend this construction technique for speed tyres. Unless you really like to see spectacular crashes.

Originally Posted by TexasSP

Bigger tires make for more weight and higher rotating mass, thus robbing you of energy that could be put elsewhere.

It's true to say that, for a given construction, the bigger the tyre, the higher the rotating mass and that this will reduce the power available to propel the vehicle forward. It's not true to say that big tyres are bad. There is a trade-off and it's therefore reasonable to assume that there is a "sweet spot" somewhere along the continuum between 2" and 8". Where that sweet spot is will depend on the construction of the tyre and wheel. Foam tyres are generally far lighter than standard rubber and so the sweet spot will tend towards the larger sizes. That said, let us remember that the fastest E-Revo so far, used 5 1/2" tyres.

Originally Posted by TexasSP

Like I said, I did the speed thing, I know what it takes. I never implied it would be easy. I can tell you though that I never got anywhere using bigger tires and gearing for them.

You did "the speed thing"? Perhaps you'd be willing to share your performance. Just because you never got anywhere with larger tyres doesn't persuade me unless you're going to substantiate your opinion with facts.

Originally Posted by TexasSP

As for snellemin's posts I was agreeing on the points about motors and then adding my own about the tires. You seem to want to pick apart little things too much. Stop being so asinine about the whole thing.

Well, I certainly congratulate you on learning a new word. It pays to enrich your word power. However, knowing words isn't everything. You need to know how to put them in an order that reflects what's going on in your head. I suggest you practice that. As for the name calling, it now becomes clear to me why you were defending Brian's post. You think insulting strangers is acceptable. Well, let's hope you don't insult some one who's carrying a gun. Oh! And before you descend into a tirade involving statements about my Mother, I'm immune to such attempts as these really only work on Americans.

[TexasSP]

Originally Posted by RootzMan

What assumptions? Assuming you don't know what you're talking about? I would have said that was self-evident.



When the vehicle in question is only going to do 3mph, cut'n'shut tyres are all well and good. I would never recommend this construction technique for speed tyres. Unless you really like to see spectacular crashes.




It's true to say that, for a given construction, the bigger the tyre, the higher the rotating mass and that this will reduce the power available to propel the vehicle forward. It's not true to say that big tyres are bad. There is a trade-off and it's therefore reasonable to assume that there is a "sweet spot" somewhere along the continuum between 2" and 8". Where that sweet spot is will depend on the construction of the tyre and wheel. Foam tyres are generally far lighter than standard rubber and so the sweet spot will tend towards the larger sizes. That said, let us remember that the fastest E-Revo so far, used 5 1/2" tyres.



You did "the speed thing"? Perhaps you'd be willing to share your performance. Just because you never got anywhere with larger tyres doesn't persuade me unless you're going to substantiate your opinion with facts.



Well, I certainly congratulate you on learning a new word. It pays to enrich your word power. However, knowing words isn't everything. You need to know how to put them in an order that reflects what's going on in your head. I suggest you practice that. As for the name calling, it now becomes clear to me why you were defending Brian's post. You think insulting strangers is acceptable. Well, let's hope you don't insult some one who's carrying a gun. Oh! And before you descend into a tirade involving statements about my Mother, I'm immune to such attempts as these really only work on Americans.

No thank you.

[snellemin]

Foam tires are nice, but would cost alot to make a set for a Revo. Well at least for me anyways.
Sandwiching 5 layers of different durometers of foam, cutting and trueing to 1cm on a 4-5" tall rim would do the trick. Foam tires are light and you can make them wider if you have the rim for it.

[BrianG]

Why not just basically "paint" the rubber on the rim? Basically a solid rubber tire fully glued to the rim, but not too thick to create a lot of weight.

[RootzMan]

All good creative inputs guys. I think Kevlar is intending to try using some kind of hydraulic hose, stretched over a wheel. If it can be done and it doesn't crush the wheel, I'd say it's got real potential. Sorry if you were hoping to keep that secret, Kev. Unfortunately, there are a gazillion different rubbers and synthetics so the chances that the formulation for a hydraulic hose is good for tyres is pretty remote but it's worth a try.

Nic Case, current RC World Speed Record holder has put a lot of time and effort into moulding tyres onto wheels and vulcanising them on the wheels themselves. I think he would admit that his results have been inconsistent so far.

I haven't been into it in any great depth as I elected to go the foam route. I used a set of Jaco foams that were originally produced for the Savage....



I needed to make up adaptors to suit the 14mm hexes...


...and in fact, they worked very well indeed. As you can see, I narrowed the front wheels by about 0.5". If anybody fancies these, together with the adaptors, send me a PM as they're just drying out in my workshop.

There was another guy who persuaded John's BSR to make up a set of big foams for his E-Maxx. They were narrower than mine and cost him a whole lot without much success.