No Runtime!!!

Hey guys I have searched the forums to find some help with my problem.
I need help. I have an ofna hyper 7 and here is the setup mm speed control feiago 7xl motor and a 123 batteries. I have a 16 tooth pinion on the motor and the buggy runs fine,(very fast) my problem is it has no runtime my battery setup is 4s2p and the runtime is less than five minutes!!!! With a 13 tooth pinion the run time is about 20-25 minutes... I have a hyperion charger 610i duo to charge the batteries. I have them hooked up in the buggy in parallel. What tooth spur is in the hyper 7? Am I that much overgeared?

[suicideneil]

I think the trouble is you're running on too low of a voltage and gearing up to compensate for the lack of speed, hence the short run times. 5s2p (if it'll fit) of A123 batteries would be much better, then you could run the smaller pinion and get about the same speed, with longer run times to boot I bet. Hopefully more opinions will follow.

Is the factory diff in the hyper 7 46, 48, or 51 tooth?

Look what i've find on Tower Hobbies, the red outline one:

NOTES FROM OUR TECH DEPARTMENT

This is the 1/8 scale glow powered, radio controlled, ready to run
Ofna Hyper 7 TQ Pro Off Road Racing Buggy.

FEATURES: Chassis: 0.12" (3.2mm) hard coated countersunk aluminum chassis
Drive: Four wheel drive shaft drive
Aluminum: Shock towers, bellcrank plate, fuel filter and
suspension arm plates
Graphite: Radio tray plate, transponder mount and bellcrank/front
chassis brace
Torsen braces: Front and rear one piece, purple anodized
Radio: 2-channel 27MHz AM with steering and throttle trim and reverse
two servos, charge jack on transmitter
Engine: Ofna .28 MacStar .28 cu in (4.6cc) with glow plug, slide
slide valve carburetor and pull-starter
Exhaust: Two chamber polished natural finish aluminum tuned pipe
Fuel Tank: 4.6oz (135cc) flip top cap
Clutch: 3-shoe
Transmission: Single speed
Ball Bearing: Full set
Shocks: Oil-filled, anodized aluminum body with coil over spring,
0.14" (3.5mm) shaft diameter and rubber shock shaft boots
Clutch Bell: 14 tooth
Main Gear: 47 tooth, steel construction Gearbox: Sealed, both Front and Rear
Differentials: Front, center and rear planetary differentials
Brakes: Single disk front and rear with Feonado pads
Tires: 4-1/4" (102mm) diameter 1-5/8" (41mm) wide Avenger tires
Wheels: 3-1/4" (81mm) diameter 1-5/8" (41mm) wide that accept a
17mm drive hex
Body: Painted and trimmed buggy body
Bumpers: Front high strength
Suspension: Front and rear double wishbone with CNC milled 7075
rear components, hard coated suspension plates
Caster: Adjustable, caster/toe-in refers to the angle of the front
suspension when viewed from the side of the car in relation to the
chassis
Camber: Adjustable, camber refers to the angle of the tops of the
tires from vertical when viewed from front or behind vehicle
Steering: Plastic Bell Crank
Servo Saver: Included, built into the right bellcrank

INCLUDES: Hyper 7 TQ Pro rolling chassis with aluminum shocks, six universal
drive shafts, painted body, tires, foam inserts, wheels, wrench
aluminum front and rear braces, 47 tooth spur gear, fuel bottle,
14 tooth clutch bell, MacStar .28 engine, 4-way wrench, extra
shock pre-tensioners, D-size glow starter and photo-ilustrated
manual

REQUIRES: AA Batteries: 12, eight for radio and four for receiver
D Battery: 1 for glow starter
Misc. Items: Building and track equipment
Fuel: 2-cycle glow fuel with 10%-15% nitromethane, 16% lubricant-
Most of the fuels we carry meet or exceed the lubricant content
required for optimum performance and maximum engine life. In the
past, the conventional lubricant content used in fuel was 18%. But
with new advanced technologies, fuels like Red Alert and O'Donnell
for example, have a better quality of lubricants even though the
percentages of lubricant content are lower. These high-tech
lubricants provide exceptional cooling and protection.

SPECS: Vehicle-
Length: 19.6" (498mm)
Width: 13.8" (310mm)
Height: 7.3" (185mm)
Weight: 7.7 lbs (3500g)(approx.)
Wheelbase: 12.9" (327mm) (wheels on-center front-to-rear)
Tread- Front- Rear- (wheels on-center side-to-side)
Front Track: 10.2" (258mm)
Rear Track: 10.2" (258mm)
Tires- Front: 3.2" x 1.7" (81x43mm)
Rear: 3.2" x 1.7" (81x43mm)
Body-
Length: 15" (380mm)
Width: 8-5/8" (220mm) at widest point
Height: 3-3/4" (95mm)

COMMENTS: For Replacement Ball Bearings use:
Qty. Size Location Bearing Set Qty.
(18) 8 x 16mm front & rear diff gears, axles (use 1 DTXC1587)
(use 4 DTXC1585)
(2) 6 x 10mm steering bellcrank (use 1 DTXC1561)
(2) 5 x 10mm clutchbell

[BrianG]

Just the fact that reducing your pinion drastically improved runtime proves that you're geared too high. Like suicideneil suggested, go with another cell to gain higher voltage and then gear down to around 14T, and you will be much happier I think.

Thanks for the info. Will the mm esc run the a123 in a 5s config?

[suicideneil]

Should do fine- just doesnt like 5s lipo, but 5s A123 is a common setup (with external BEC).

Thanks, built a pack and ran the car on the 16 tooh pinion. My 13 was not hardened and is toast. The battery at the end of my five minute run was at about 13 volts and the hyperion did not like it. The charger would not charge the battery. Had to charge it as a four cell for about five minutes before the charger would let me charge it as a five cell. I have 13 tooth pinion on the way should be here on Monday.

[Hydrodancer]

Can you post pictures of your set up? I'd like to see how you fit all those cells.

I will post some later this week.

I have my 13 tooth pinion on the buggy and now I have the same problem as before. Three minutes of run time per pack four or five cells. I think my charger has a setting I can't find. When the 5s1p pack comes off the car is is aroung 9 volts. I have to charge it as a 3 then a 4 then a 5 cell pack on my hyperion charger 610i. This whole process takes less than five minutes until the charger stops. Does anyone know what setting I need to change to get the charger to charge my batts?????

Sorry no pics yet. The track I run at has gone to a 30-35 minute main and I have decided to go lipo of the runtime. Will post pics of the new setup as soon as I get the batt tray I ordered yesterday. If anyone is interested in my old batts just pm me.

[lutach]

That's really odd with the A123. When I was setting my truck for some speed runs, I actually ran it on 10S1P for over 10 minutes and I could've went longer, but it was too fast for the place I was testing it. Have you tried running a different motor?

With the 13tooth pinion on the track I race on with alot of jumps and a 110 foot striaght the buggy will run about 11 minutes on the 5s1p config. It is very fast, but since the mains are from 30-35 minutes long that is a lot of battery changes. I am going lipo to try and find a way to run the main on one or two batteries.

[lutach]

The A123 can go as low as 2 volts per cell and maybe you might be hitting the cut off voltage set in the controller.