Newb guides?

[Cassp0nk]

Hi,

I've been having a search, but can't find any info on selecting the correct brushless motor + pinion for a car, and what factors impact this? Can anyone recommend a guide which explains all of this?

I'm considering getting the following setup just from looking at what people are running, but not sure what pinion would be appropriate and what the considerations are when deciding.

Cat SX
Losi xcelorin 6.5 ESC + motor
spectrum dx7r
team associated ds1015

Also not clear on how the batteries work from a few comments on here. I thought that the main difference between a lipo with 3400 vs 4900 say, would be runtime, but I've seen comments implying the 4900 would be faster?

Thanks for any help, I'm sure this stuff is all written up somewhere so if someone could point me at it that would be wonderful!

Dan

[Alfonzo]

Pinion (and/or spur gear) are determined by the overall gear ratio you need to achieve - i.e. how far your buggy will move forwards for every revolution of the electric motor. This ratio is largely determined by the motor / battery combination, and then partly by track conditions & driving style. The smaller your pinion gear (or bigger your spur gear) the greater your acceleration but lower your top speed, and vice-versa. The reality is there is a pretty small tuning range as the motors don't like excessive gearing. Suggest you post this question on the Schumcher section and someone will give you a suggestion, or wait until you read the manual that comes with the car as will almost certainly have a chart or something. Each type of car is differrent due to differing internal ratios. Definitely get this right, so good question to ask.

Regarding the Lipo's - you also need to consider the 'C' rating, which is a measure of the discharge ability. The larger this number, the greater the ability of the Lipo to allow the motor to draw current, which translates into acceleration on the track. It think I've got that right..haven't actually got any Lipo packs meself.:)

[Cassp0nk]

Thanks (and also for the loctite thread reply).

Is there a guide saying how many turns is appropriate for what car? I just looked at some race results with Cat SXs in and they were all 5.5 or 6.5, with perhaps one 4.5. Does fewer turns equate to less torque but higher top speed?

[sosidge]

Thanks (and also for the loctite thread reply).

Is there a guide saying how many turns is appropriate for what car? I just looked at some race results with Cat SXs in and they were all 5.5 or 6.5, with perhaps one 4.5. Does fewer turns equate to less torque but higher top speed?

Sadly there are no guides outside of experience and rules of thumb. Looking at tech charts is about as good as a resource as you will get!

Certainly a 6.5 is not the wrong motor for a 4wd buggy, you will find it a little easier to drive than a 5.5, and often easier to drive is faster round the track anyway!

Lower turn motors generally rev higher, create more power, and create a little less torque. Gearing is based on the "feel" of the car on the track (gear down for more punch, gear up for more top end, within reasonable limits), and also to stop the electrics from overheating. Although brushless motors tend to have ample punch with any gearing.

Curious as to why you are choosing a Spektrum DX7 and the Ace servo tough - wouldn't be my first choice for electric buggy racing. DX7 is a flight transmitter, Ace is a fine servo but more intended for nitro.

[Cassp0nk]

Sadly there are no guides outside of experience and rules of thumb. Looking at tech charts is about as good as a resource as you will get!

Certainly a 6.5 is not the wrong motor for a 4wd buggy, you will find it a little easier to drive than a 5.5, and often easier to drive is faster round the track anyway!

Lower turn motors generally rev higher, create more power, and create a little less torque. Gearing is based on the "feel" of the car on the track (gear down for more punch, gear up for more top end, within reasonable limits), and also to stop the electrics from overheating. Although brushless motors tend to have ample punch with any gearing.

Curious as to why you are choosing a Spektrum DX7 and the Ace servo tough - wouldn't be my first choice for electric buggy racing. DX7 is a flight transmitter, Ace is a fine servo but more intended for nitro.

Thanks for the response.

So is stopping me getting a 4.5 and then using the throttle map in the ESC to limit it to 70% power say? Is that equiv to using a 6.5 in terms of drivability if the torque differences are fairly negligable? Given all the motors are the same price, I'm wondering why not get the fastest?

Well spotted on the Radio, I meant DX3R!

Wasn't sure on servo but M-K-Racing had it in stock and I saw a few people used them in CATs. They no longer have it on their website today though and only have Savox that I've never heard of? +- 15 quid on the servo doesn't bother me, so wanted to get the best in the 40-70 quid bracket. Having said that, the Savox has titanium gears which has to be good?

[sosidge]

Thanks for the response.

So is stopping me getting a 4.5 and then using the throttle map in the ESC to limit it to 70% power say? Is that equiv to using a 6.5 in terms of drivability if the torque differences are fairly negligable? Given all the motors are the same price, I'm wondering why not get the fastest?

Well spotted on the Radio, I meant DX3R!

Wasn't sure on servo but M-K-Racing had it in stock and I saw a few people used them in CATs. They no longer have it on their website today though and only have Savox that I've never heard of? +- 15 quid on the servo doesn't bother me, so wanted to get the best in the 40-70 quid bracket. Having said that, the Savox has titanium gears which has to be good?

Limiting throttle travel is not a path I would go down. Select a motor for the track based on what it does at full throttle.

Just because something has titanium in it doesn't mean it is any good... having said that I know nothing about the Savox servos so couldn't comment. I only buy Futaba nowadays after a few disappointing experiences with budget brands.

[Alfonzo]

I see what you're saying about running a 'hot' motor then throttling it back, but in practice this isn't the best idea. Better to get a less hairy motor and let it run un-restricted, I belive this would be more efficient and smoother, etc although couldn't back that up with any theory.

Have you got much RC car track experience? If you haven't, best bet is to get yourself stuck in without getting too bogged down in the technical details. The kit counts of course, but the thumbs are where it's at ;).

[Dagger Thrasher]

If you're looking for a good guide on LiPos, then this an essential read: http://www.glypo.com/guides/lipo/. It's important that you read up on what LiPo packs to choose and how to take care of them, so I'd suggest you have a good read through that article.:)

[Cassp0nk]

Thanks. Will take a look at that as I've read his other reviews. Bought my setup now :)