1/8 buggies and electric conversions some questions - RC-Monster Forums

nativepaul · 02.09.2013, 10:37 PM

Don't kid yourself that its low power just because its a small motor.

A motor will draw as many amps as it needs to to pull the gearing you have at the speed its KV and voltage determine, a bigger motor just has more thermal mass to heat up slower and more surface area for better heat disipation, a 7XL will handle more power than a 7L for extended periods while keeping cool enough for a long service life due to the aforementioned better cooling. The 7L and 7xl have the same number of turns, and the same diameter rotors and cans, making it very likely that they both have the same gauge wire making up the windings, if we look at short term power capability the windings will fuse at the same amp draw and the same voltage is on both so the are capable of the same absolute power.

The 7L is 3511kv which on 4s is about 50,000RPM, a 7XL is 2382kv which is about 33,350RPM, so if the gearing is the same the 7L will be pulling a lot more power than the 7XL in order to spin the extra speed. As gears get rather inefficient at 11teeth and under so if I assume you use a 12t pinion with typical buggy 3.3:1 diff ratios and 4.5" tyres, it is geared for 50 mph (+any ballooning) and pulling more than average amps to do so (most buggy racers seem to gear for about 40mph depending on the track), a 7XL in the same buggy would be up to an 18 tooth pinion before it is making the same power as the 7L.

Torque is not only related to the size, magnets, pole count and KV of the motor but to the current flowing through it, while a huge low KV motor like the 1717 will have a much higher KT than than the 7L, .86oz-in/A vs .39oz-in/A if the little 7l is screaming its guts out on 4s about to melt it will have MANY more Amps flowing though it than a 1717 running cool on 6s and could be producing dogbone breaking torque.

A 7L is not really suited to 4s, you would be better off on 3s with a 13tooth pinion which would give you 40mph, cooler running, and less breakages. if you want to stick with 4s I would recommend a motor with a much lower KV (somewhere in the 2000 range), and though I have several, I wouldn't recommend a Feiago nowadays, Leopards are a fair bit more efficient for not much more money.

_paralyzed_ · 02.12.2013, 10:37 AM

Also, as far as buggies go, those two are kinda cheap/weak.

The ultra's are the base entry level model for ofna. RD Logics is really more of an aftermarket parts company than a reputable vehicle manufacturer.

I have an ofna ultra lx1e and with proper setup (shimmed diffs, thick center diff fluid) it is a good buggy, but nowhere near as stout as my ofna hyper 8.5.

If I were you I'd give the ofna another go and I'd sell the rd logics to some schmuck on e-bay.

And to answer your original question, buggies are the most durable 1/8 scale r/c's out there. The low weight, and low rotational mass of the wheels and tires keep parts happy.

You've just had a bit of dumb luck.

Thirdgen89GTA · 02.12.2013, 01:00 PM

Quote:

Originally Posted by _paralyzed_

Also, as far as buggies go, those two are kinda cheap/weak.

The ultra's are the base entry level model for ofna. RD Logics is really more of an aftermarket parts company than a reputable vehicle manufacturer.

I have an ofna ultra lx1e and with proper setup (shimmed diffs, thick center diff fluid) it is a good buggy, but nowhere near as stout as my ofna hyper 8.5.

If I were you I'd give the ofna another go and I'd sell the rd logics to some schmuck on e-bay.

And to answer your original question, buggies are the most durable 1/8 scale r/c's out there. The low weight, and low rotational mass of the wheels and tires keep parts happy.

You've just had a bit of dumb luck.

Pretty much this. The Ultra series uses cheapo cast metal for the diffs. The Ultra line is from Hong-Nor, and while they produce a ton of models, the only GOOD Hong-Nor cars are the Jammin/Nexx series. These are their competition level stuff.

Diff problems have always been an Ultra liability.

ZippyBasher · 02.12.2013, 05:20 PM

Quote:

Originally Posted by Thirdgen89GTA

Pretty much this. The Ultra series uses cheapo cast metal for the diffs. The Ultra line is from Hong-Nor, and while they produce a ton of models, the only GOOD Hong-Nor cars are the Jammin/Nexx series. These are their competition level stuff.

Diff problems have always been an Ultra liability.

HIGHLY DISAGREE

As Paralyzed said, it was probably just dumb luck with the Ofna. There is noting wrong with the Diffs on the LXe. My dad has been beating his for over 2 years with a 1717 and 6s. No Diff rebuilds front, center or rear. Please shim your diffs and they will hold up to ANYTHING you can throw at them. The buggy tires will break traction before you break a diff if they are assembled correctly...

Give the LX2e a second try, they are the best buggy for the price... The only "upgrade" it needs is an aluminum rear toe plate. after that its a TANK.

Thirdgen89GTA · 02.12.2013, 07:00 PM

Quote:

Originally Posted by ZippyBasher

HIGHLY DISAGREE

As Paralyzed said, it was probably just dumb luck with the Ofna. There is noting wrong with the Diffs on the LXe. My dad has been beating his for over 2 years with a 1717 and 6s. No Diff rebuilds front, center or rear. Please shim your diffs and they will hold up to ANYTHING you can throw at them. The buggy tires will break traction before you break a diff if they are assembled correctly...

Give the LX2e a second try, they are the best buggy for the price... The only "upgrade" it needs is an aluminum rear toe plate. after that its a TANK.

It was a bad design when it debuted, its still a bad design today.

Hobao 7 > LX line any day of the week. I'd rather convert a Hyper 7 than buy a LX2 based buggy.

For budget 1/8 e-buggies right now I'd be all over the Nexx8, its actually meant to race and compete on an even level and its an evolution of the Jammin series cars which have proven track records.

ZippyBasher · 02.12.2013, 07:10 PM

Its not a bad design, It keeps up with my 8ight just fine.

But this wasnt about racing... It was about a weak differential. Which is not any weaker than any other 1/8 diff I've used and rebuilt.

Bottom line is the LX2e is a GREAT STARTING/BASHING BUGGY, If your into racing you probably wouldnt want an entry level buggy in the first place. IMO

_paralyzed_ · 02.12.2013, 07:14 PM

Quote:

Originally Posted by ZippyBasher

HIGHLY DISAGREE

As Paralyzed said, it was probably just dumb luck with the Ofna. There is noting wrong with the Diffs on the LXe. My dad has been beating his for over 2 years with a 1717 and 6s. No Diff rebuilds front, center or rear. Please shim your diffs and they will hold up to ANYTHING you can throw at them. The buggy tires will break traction before you break a diff if they are assembled correctly...

Give the LX2e a second try, they are the best buggy for the price... The only "upgrade" it needs is an aluminum rear toe plate. after that its a TANK.

In the buggy world ultra diffs are known to be a weak link... shimming helps tremendously.

ZippyBasher · 02.12.2013, 07:32 PM

Well.... Maybe I am the one with Dumb (read GOOD) Luck.

We have an old Ultra LX with a 1518 and 6s my brother drives and
My dad's LX1e with 1717 and 6s. Not one broken diff yet. 2+ years running.

_paralyzed_ · 02.12.2013, 10:54 PM

Quote:

Originally Posted by ZippyBasher

Well.... Maybe I am the one with Dumb (read GOOD) Luck.

We have an old Ultra LX with a 1518 and 6s my brother drives and
My dad's LX1e with 1717 and 6s. Not one broken diff yet. 2+ years running.

My lx1e's diffs are fine too, on 6s with a 1515. I believe newer diffs may be stronger. My Ultra nitro buggy ate diffs all the time.

They just have a bad reputation, that is all we're saying.