Boat Gearboxes.

[harry smith 1Participant @harrysmith1]

[harry smith 1Participant @harrysmith1]

Hi All

Found a good car gearbox on Banggood with motor mount for a 540 or 35mm brushless motor.

Double 5mm output shaft with a 87 teeth main gear.

As you can get pinion gears from 13 to 28 teeth, this gives you ratios between 6.69 and 3.11.

The mount holes are space 11 mm one way and 22mm the other.

If mounted on the side with an aluminium angle bracket, it would sit low in the boat.

They also have stainless uni joints 5mm to 4mm, 5mm to 5mm and 5mm to 6mm( part No.976297).

Gearbox part No.1172466.

I think you adapt a 28mm motor to fit.

Harry Smith

[harry smith 1Participant @harrysmith1]

Hi All

I miss the size of the gear box.

W= 75mm

H=65mm

L=35mm and with a 540 motor and pinion gear 75mm.

Harry Smith

[ashley needhamParticipant @ashleyneedham69188]

Harry. Very useful, and good for getting that larger prop on for increased propulsive efficiency.

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by ashley needham on 17/05/2018 18:41:39:

Harry. Very useful, and good for getting that larger prop on for increased propulsive efficiency.

Ashley

…and you can also get a lower prop shaft line if needed.

[harry smith 1Participant @harrysmith1]

Hi All

Spur teeth for ratios

13T=6.69

14T=6.2

15T=5.8

16T=5.44

17T=5.12

18T=4.83

19T=4.58

20T=4.35

21T=4.14

22T=3.95

23T=3.78

24T=3.63

25T=3.48

26T=3.34

27T=3.22

28T=3.11

If the bracket was 80 degree angle the centre of the output shaft is about 25mm from the bottom of the angle.

Smallest plate size of 100mm x 75mm you can also mount a Msonik 20Amp ESC.

Harry

[harry smith 1Participant @harrysmith1]

Hi All

Made the motor mount today, so 25mm from the bottom of the bracket to the centre of the shaft is the minimum I got it down to with a 80 degree angle.

I have added the pattern for the mount and mark out one place for a MSONIK 20Amp ESC, but they is more room for a larger one if required.

Only one mount hole will be a bit hard to get at, but slotting it would make it easier.

Harry Smith

[harry smith 1Participant @harrysmith1]

Hi All

My mate workout that the gears inside the case have a 2and1/2 to 1 reduction as well.

Sorry guys I miss this one !!!!

Harry

[harry smith 1Participant @harrysmith1]

Hi All

One of the club members said drop the big gear and use the 2 and 1/2 ratio inside work great !!!

I did not think of that one !!!

Harry

[harry smith 1Participant @harrysmith1]

Hi All

Tested it out today, so noisy!!!!

Pull it to bits and added tap silicon grease inside also grease the outer gears.

What a difference !!!

I work out the spur teeth number to 25 with the 5000kv motor( I have) on 3S will get me to 6379 rpm.

This is under the maximum rpm for a Raboesch 3 blade A type 55mm prop.

Ratio 8.7 to 1.

So is the power times the ratio ??

Harry Smith

[ashley needhamParticipant @ashleyneedham69188]

Not sure what you mean there Harry?? Power times ratio?? please explain. Ashley

[Dave MilbournParticipant @davemilbourn48782]

Harry

Are you seriously running a motor at 55,500RPM {5000kv x 11.1v} into a plastic-geared gearbox? How long do you expect it to last?

Dave M

[harry smith 1Participant @harrysmith1]

Hi Dave

These gearboxes run up to 5000kv motors in cars !!!

The internal gears are 5mm wide, but, dropping off the motor mount and 87 tooth gear you end up with a very good 2 and 1/2 to 1 ratio.

The output change to an input shaft (4mm) would make a strong gearbox for $17au.

I only quoted the 5000kv because I have one in stock.

So does the power increase with the 2 and 1/2 ratio by 2 and 1/2 times e.g. 100 Watts to 250 Watts and the revs of course drops 2 and 1/2 e.g. 16650 to 6660 rpm ???

Which would be an 1500kv motor on 3S !!!

Harry Smith

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by harry smith 1 on 28/05/2018 10:51:50:

I work out the spur teeth number to 25 with the 5000kv motor( I have) on 3S will get me to 6379 rpm.

This is under the maximum rpm for a Raboesch 3 blade A type 55mm prop.

Ratio 8.7 to 1.

So is the power times the ratio ??

Harry Smith

The power remains the same, less whatever is lost in the gear train. The torque is what increases as the output revs decrease due to gearing.

I don't know if its a trick of the light, but that slight roughness that appears on the motor pinion could chew lumps out of the plastic gear rapidly at high revs.

[harry smith 1Participant @harrysmith1]

Hi All

I have decide to remove the motor mount and large plastic gear, also cutoff the thread end of the 4mm large gear shaft.

Make a new motor mount with a uni joint between.

Then I can use lower kv motors and small ones as well .

Checking out the bin box found Prop Drive 2836-1800kv 438 Watts( 19980 rpm on 3S) for a test motor.

The Watts rating is for 4S, so it would be lower.

It is still over the 6400 rpm mark I am aiming for, but, I can cutoff the maximum range on the throttle of the transmitter.

The 1400kv motor fits the bill nicely.

I will kept playing with this as WINTER is Tasmania has arrived !!!!

Harry Smith

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