CARS II

My Feedback: (7)

The engine is a TJT 3000 ( 27 lbs thrust ) these engines come from Australia, they were build with Artes hot parts and parts machined by them, I had mine since new, around 14 hrs total run time, I used it in my Boomerang XL and now on a Roo, today the starter did not engaged the compressor, it has done this now and then lately, today was a complete no go 😩 it uses a grommet in the bendix instead of an O ring.

I took the starter out of the casing and started the motor a few times, I also added a couple of drops of oil to the bendix to help it move, I noticed during the start up that the starter motor runs just fine, the bendix comes forward some and then it retracts backwards to the stand by position, the motor is still running when this is happening.

My assessment is that the motor is not spinning fast ( strong ) enough to make the bendix come forward and engage the compressor nut.


Any suggestions as to which motor can I use to replace the starter motor?


Thanks.

CARS II

My Feedback: (7)

mongo

My Feedback: (15)

if it is a 2 wire motor, brushed, most of those older units of most every brand used the commonly available mabuchi car motors for starter duty. a 540 i think, been a long time.
you could try replacing it with a similar sized brushed motor, if you can still find one.

CARS II

My Feedback: (7)

Thanks mongo, I knew about the replacement motor but, wanted to consult with you guys, I will swing by he LHS car side to see if the can help, I also know I could get it on line.

And yes, it is a two wire brushed motor.

Old Roo, new engine mount

Ruizmilton

My Feedback: (29)

Actually, depending on the engine, it’s either a speed 300 (24mm diameter can) or speed 400 (28 mm diameter can) motor, a 540 is way too big. The “Speed” naming comes from when Graupner used to market them for early electric rc prop planes. The correct Mabuchi number for the “300” I think is 380 and you need to make sure it’s rated 6 volt and has a steel backplate, if it’s plastic, it’s the wrong motor and will only last a few minutes. You can find the Graupner motors on Ebay, I did a quick search and found two of the “300” and one of the “400”

rcmigpilot

My Feedback: (26)

Take a good look at the motor, there should be a part number of some sort. Several year ago I had to replace the starter on an old Ram 1000. I was able to find the Mabuchi number and found the same motor being sold at Tower under the Electrifly brand.

CARS II

My Feedback: (7)

Thank you all for the excellent suggestions.

Kelly W

My Feedback: (2)

Many-many years ago I worked with these guys. its a speed 480 motor, I think 7.2V. There were 2 versions of the clutch. The 1st was a grommet in a brass Bendix like yours, with the edges of the grommet carved down. Simple and yet very effective, but it could wear out quickly and lose torque capacity. The 2nd one was more complicated but more durable, using an O-ring.

I'm betting you just have a friction issue. If the Bendix fails to grab, it will retract as soon as the started motor acceleration drops. the Bendix is pushed out with acceleration. Once in contact the Bedix gets jammed and waits for the turbine to overtake the motor RPM, but if the acceleration drop before it grabs, it will retract and just spin freely.

I once had thee same as you are experiencing. I managed to get it working again for a little while by just turning the grommet around. You'll probably notice a cone mark ground in the grommet.

Kelly

CARS II

My Feedback: (7)

And Kelly hits the nail right on!!

I removed the starter and observed the bendix do exactly as described by Kelly, friction is the issue here, I’ve experienced this situation a few times before, the solution has always been to change the grommet, for some reason it looses its grabbing power and a new one, been soft has the capacity to grab the compressor nut.

This time I wanted a to see if I could increase the time between grommet changes by installing a new starter motor, I’m going to change the grommet, I got a couple of them in reserve for this reason.

I posted my dilemma here hopping for someone to post a solution I could implement to reduce or eliminate this problem, Kelly has given me the info that I was looking for.

Thank you Kelly for posting that info.