Midnight Pumpkin: Loss of Wheelie/Power?

[Pumpkin2 2]

Hi everyone! I'm new to the forums and the Tamiya Club site. I was way into the Tamiya kits back in the 80's and recently discovered the re-release of the Midnight Pumpkin, the original kit that got me into RC. Hence the screen name.

I bought the Black Edition kit a few weeks ago, had a great time building it, ran it around my driveway/back yard and it was fun. But I soon wanted a larger space to run and some fun terrain, so I brought the Pumpkin to a baseball field and park a few blocks away. I ran on some bumpy grass, a few hills and a dusty, dirty baseball field. I ran one battery pack all the way down. I then took about a 5 min break and put in another. I noticed there wasn't as much power and I couldn't pop wheelies. Before I could pop wheelies on demand. I attributed this to the battery having sit and maybe not having a good charge. It was a colder day than I expected so I thought this may have harmed the batteries.

The next day I went in the back yard with a fresh pack and noticed that the problem persisted. I see a decrease in speed and definitely not enough power to wheelie from a stop. One thing I also noticed was that the car sounded different. Before I had a high-pitched motor sound at full throttle. Now, it sounds lower pitched.

A few things I've checked:

• Can't hear any gear slippage.
• Took the motor off and checked the pinion and the gear it touches. I saw no breaks or evidence of an issue or slippage. Nothing obvious anyway.
• The motor was seated/screwed in tightly. I made sure to re-attach it tightly.
• No evidence of loose connection between the motor and the ESC.
• Re-programmed the ESC. Wasn't receiving any faults or beeps of any kind. Did this as precaution.
• Checked the battery packs with a volt meter. They've shown over 8 volts at full charge.

I don't have an ESC to swap out nor do I have another motor. I do have a meter so I was wondering if I should check the wires from the ESC to the motor but I'm not sure what I should see there. I was planning on upgrading to a Sport-Tuned anyway so I ordered one....

So... What are your thoughts here? Anything else I should try? Should I just swap the motor out with the new one when it comes in? Any advice is appreciated. Thanks!

[Saito2 8568]

Hi, and welcome to the forum! That's a nice paint job and rims on your Pumpkin. As far as your loss of wheelie power, I can give you two instances where I had the same problem back in the day with my Lunch Box (same chassis). Once a small pebble (from a ball field) got into my stock silver can motor and chipped a brush. The motor did sound lower pitched as it would no longer wind up to full rpm properly. Also, the rear tires can sometimes slip on the rims. Without proper bite, no more wheelies. Some folks glue the tires to the rims, but I just put a wide rubber band around the wheel where the tire bead sits to give it grip. I'm not sure if either are your issue, but it gives you something to try. Good luck.

[Pumpkin2 2]

33 minutes ago, Saito2 said:

Hi, and welcome to the forum! That's a nice paint job and rims on your Pumpkin. As far as your loss of wheelie power, I can give you two instances where I had the same problem back in the day with my Lunch Box (same chassis). Once a small pebble (from a ball field) got into my stock silver can motor and chipped a brush. The motor did sound lower pitched as it would no longer wind up to full rpm properly. Also, the rear tires can sometimes slip on the rims. Without proper bite, no more wheelies. Some folks glue the tires to the rims, but I just put a wide rubber band around the wheel where the tire bead sits to give it grip. I'm not sure if either are your issue, but it gives you something to try. Good luck.

Thanks Saito2! I'll definitely try the rubberband thing. Your thought on the motor brush getting chipped also sounds like a possibility.

[WillyChang 1820]

Stock silvercan motor, Sport Tuned & everything else in a sealed can - not unknown for the stubby brush to fall off its 'arm'. 

Take a peek thru the oval vent holes, see if there's anything amiss inside. 

[StrokerBoy 772]

Wheels spinning inside the tyres is the first thing to check, that's usually what it is.

[Pumpkin2 2]

13 hours ago, WillyChang said:

Stock silvercan motor, Sport Tuned & everything else in a sealed can - not unknown for the stubby brush to fall off its 'arm'. 

Take a peek thru the oval vent holes, see if there's anything amiss inside. 

I'll definitely do so, thanks!

[Pumpkin2 2]

5 hours ago, StrokerBoy said:

Wheels spinning inside the tyres is the first thing to check, that's usually what it is.

Great idea, thanks! Looking for the right sized rubber bands now...

[Darat76 267]

my first question is, how long was the first run? 10 mins? 15? 30? an hour?

are the batteries nimh, lipo, or life?

did you build the car with ball race bearings? or with the plastic kit supplied bushes?

after the run did you do the touch test on the motor and the esc? if so was either uncomfortably hot to keep touching?

[Pumpkin2 2]

On 3/25/2017 at 5:45 AM, Darat76 said:

my first question is, how long was the first run? 10 mins? 15? 30? an hour?

are the batteries nimh, lipo, or life?

did you build the car with ball race bearings? or with the plastic kit supplied bushes?

after the run did you do the touch test on the motor and the esc? if so was either uncomfortably hot to keep touching?

Turns out it was the motor. When I upraded the motor, cleaned it up and added the rubber bands in the tires it was back to normal, even better.

I run standard 2000 and 3000 Mah Nimh packs. Metal bearings throughout. There was no excessive heat on the ESC or motor. I did check. Just a performance, loss of torque and an overall speed drop. I at first thought it was a battery issue but as I mentioned, it wasn't.

[Pumpkin2 2]

Been using my phone to get some shots of the Pumpkin in action. Cut a few together:

 

 

[Munchbox 100]

My Lunchbox did the same thing on the silver can. After a nice thick set of rubber bands I'm now running a 2400kv brushless and 18t Hornet pinion with no trouble. I've recorded speeds from 24-28mph several times and drag neck and neck with a 4400kv brushless EcX Ruckus