Carisma F14 Blog - Part 3
We continue this enlightening series with the 3rd part of Dez Chand's Carisma F14 blog.
It?s time to power up and roll out, so choose your equipment wisely and it will serve you well for many seasons to come. We?ll start with battery selection and installation orientation.
Battery Fitting
Although the chassis will accept a micro NiMH pack the world has moved on a pace and now everyone wants LiPo power. Fortunately the F14 lends itself to the latest battery technology very well. The little 1800mAh 2S FTX ?Voltz? LiPo sat across the chassis without any overhang, which seemed best for quick battery changes. The tape slots in the chassis are handy and I soon had the cell well attached, though I noticed it sat on the 'T' bar. In a bid to avoid affecting the rear suspension movement I used double sided tape to fix a small square of lexan either side of the T bar to jack the battery up, job done.
Space the battery up to clear the 'T' bar.
Then I tried fitting the battery down the centre of the chassis and that suited me better, leaving room either side for the receiver and speed controller.
The FTX ?Voltz? LiPo fits the Carisma F14 perfectly and measures just 30x19x90mm but a slightly longer cell could be accommodated in the longitudinal position, up to 105mm long simply by moving the front retainer to its forward position on the upper chassis deck.
By design the front lower chassis brace and rear tweak screw housings incorporate ledges and guides to hold the battery clear of the 'T' bar which is great, and there is a removable front battery retainer which suggests you can remove the battery out the front of the chassis by sliding it past the steering servo, but I found the top deck needed removing to get proper access.
Having tested the F14 indoors at Ardent Raceway, then raced the F14 several times at the smaller indoor Wednesday night Bedworth club and once outdoors on the full Bedworth tarmac track too, I can confirm that the 1800mAh battery needs nothing more than a quick top up here and there to see me through a whole meeting because the car is so lightweight and the typical 2WD F1 driving style demands a careful trigger finger. I am confident there is no need to swap batteries between heats so I stuck with the longitudinal installation along the centre of the chassis.
Placing the battery longitudinal gives the best radio and ESC locations.
The front battery retainer has a choice of two holes, it?s in the forward position as supplied but needed to be moved to the rear hole to suit the FTX ?Voltz? LiPo pack. The retention was very good, the top deck holds the battery down snuggly, the side walls of the rear tweak posts keep the battery central and the removable front retainer keeps the cells from moving around.
Power Plants
The little Carisma GT14 motor is a gem, with just enough timing advance to get a whopping 46,000rpm at 7.2V. The motors do not cost the earth, and are designed with replaceable brushes and springs so maintenance is a breeze. Brushes/spring sets are very cheap so the running costs for these motors makes them very tempting indeed. The R14 motor is a similar beast but with zero end bell timing the revs are a little lower and hence the torque is a little higher. A pair of M3 mounting holes are 17mm apart (between centre's) so line up perfectly with the F14 alloy motor pod slots.
Voltz LiPo battery with a Carisma's motor (left). The Etronix Probe ESC (right).
I always run the 3.5mm gold connectors on my micro batteries and ESC?s, and take the opportunity to put them in line with the motor too for easy removal without the need for a soldering iron. The power transfer and minimal losses make these little plugs a favorable alternative to the two pin square plugs provided on the ?Voltz? LiPo and the typical Tamiya plug and bullets of the Etronix Probe ESC that we decided to fit in the F14 to get it going. I always use a male connector on the battery positive, female on battery negative with mating halves on the ESC so I can NEVER plug the battery in backwards no matter how big a rush I?m in. Soldering some thinner more flexible wires into the ESC and routing them carefully to the motor means I have enough slack to remove the motor for maintenance, and enough free length to flex without affecting the rear suspension pod movement or inducing any tweak.
Connectors replaced.
Working out the gear ratio, the 49.5mm diameter (155.5mm circumference) rubber rear tyres, 80 tooth spur and 12 tooth pinion (6.66:1 ratio primary drive) provided in the kit means a roll out of 23.3mm/rev, and at 46,000rpm this gives a top speed of 1071 m/minute or 64.3kph (40mph) which is pretty scary for a 1/14th vehicle, a scale speed of 562mph! You can bet there are a few F1 teams that would love that kind of top end!
This amount of power made the F14 very twitchy, so I had to reduce the throttle end points to around 60% in order to keep the kit rubber tyres from expanding at speed. Once the top speed was sensible I made some good laps of Ardent Raceway on the kit rubber tyres, as the harder front tyres afford a degree of understeer and control was predictable on the additive soaked racing carpet. The Etronix Pulse speed control was plenty smooth enough for fine control and the brakes were manageable. We knew we'd need foam tyres to really get the best out of the F14 and there are options rims to do just that, but that's another story, we'll save that for next time!
Carisma F14 inddor on rubber - Ardent Raceway.
Space the battery up to clear the 'T' bar.
Then I tried fitting the battery down the centre of the chassis and that suited me better, leaving room either side for the receiver and speed controller.
The FTX ?Voltz? LiPo fits the Carisma F14 perfectly and measures just 30x19x90mm but a slightly longer cell could be accommodated in the longitudinal position, up to 105mm long simply by moving the front retainer to its forward position on the upper chassis deck.
By design the front lower chassis brace and rear tweak screw housings incorporate ledges and guides to hold the battery clear of the 'T' bar which is great, and there is a removable front battery retainer which suggests you can remove the battery out the front of the chassis by sliding it past the steering servo, but I found the top deck needed removing to get proper access.
Having tested the F14 indoors at Ardent Raceway, then raced the F14 several times at the smaller indoor Wednesday night Bedworth club and once outdoors on the full Bedworth tarmac track too, I can confirm that the 1800mAh battery needs nothing more than a quick top up here and there to see me through a whole meeting because the car is so lightweight and the typical 2WD F1 driving style demands a careful trigger finger. I am confident there is no need to swap batteries between heats so I stuck with the longitudinal installation along the centre of the chassis.
Placing the battery longitudinal gives the best radio and ESC locations.
The front battery retainer has a choice of two holes, it?s in the forward position as supplied but needed to be moved to the rear hole to suit the FTX ?Voltz? LiPo pack. The retention was very good, the top deck holds the battery down snuggly, the side walls of the rear tweak posts keep the battery central and the removable front retainer keeps the cells from moving around.
Power Plants
The little Carisma GT14 motor is a gem, with just enough timing advance to get a whopping 46,000rpm at 7.2V. The motors do not cost the earth, and are designed with replaceable brushes and springs so maintenance is a breeze. Brushes/spring sets are very cheap so the running costs for these motors makes them very tempting indeed. The R14 motor is a similar beast but with zero end bell timing the revs are a little lower and hence the torque is a little higher. A pair of M3 mounting holes are 17mm apart (between centre's) so line up perfectly with the F14 alloy motor pod slots.
Voltz LiPo battery with a Carisma's motor (left). The Etronix Probe ESC (right).
I always run the 3.5mm gold connectors on my micro batteries and ESC?s, and take the opportunity to put them in line with the motor too for easy removal without the need for a soldering iron. The power transfer and minimal losses make these little plugs a favorable alternative to the two pin square plugs provided on the ?Voltz? LiPo and the typical Tamiya plug and bullets of the Etronix Probe ESC that we decided to fit in the F14 to get it going. I always use a male connector on the battery positive, female on battery negative with mating halves on the ESC so I can NEVER plug the battery in backwards no matter how big a rush I?m in. Soldering some thinner more flexible wires into the ESC and routing them carefully to the motor means I have enough slack to remove the motor for maintenance, and enough free length to flex without affecting the rear suspension pod movement or inducing any tweak.
Connectors replaced.
Working out the gear ratio, the 49.5mm diameter (155.5mm circumference) rubber rear tyres, 80 tooth spur and 12 tooth pinion (6.66:1 ratio primary drive) provided in the kit means a roll out of 23.3mm/rev, and at 46,000rpm this gives a top speed of 1071 m/minute or 64.3kph (40mph) which is pretty scary for a 1/14th vehicle, a scale speed of 562mph! You can bet there are a few F1 teams that would love that kind of top end!
This amount of power made the F14 very twitchy, so I had to reduce the throttle end points to around 60% in order to keep the kit rubber tyres from expanding at speed. Once the top speed was sensible I made some good laps of Ardent Raceway on the kit rubber tyres, as the harder front tyres afford a degree of understeer and control was predictable on the additive soaked racing carpet. The Etronix Pulse speed control was plenty smooth enough for fine control and the brakes were manageable. We knew we'd need foam tyres to really get the best out of the F14 and there are options rims to do just that, but that's another story, we'll save that for next time!
Carisma F14 inddor on rubber - Ardent Raceway.
Click the images below to view the other parts of the blog.
