2 rc motor with clutch

[xadmx]

hi i am planing on building this in my spare time, do you think the motors will be powerful enough do drive such a configuration. i am going to use a centrifugal clutch so i can just use rc stuff to keep it simple, all i am after is top end speeds. this is going on a 20in wheel bmx.
adam


motor specs

7000 Watts of Power for less than 100GBP

Model: XYH80-100-A
Turns: 6
Maximum Power: 7000W
Resistance: 17ohm
Idle Current: 3.5A
ESC: 150A
Input Voltage : max. 48V
Kv : 180 rpm/V
Weight: 1750g
Shaft: 12mm
Voltage Range: 20-48v
Non Load Current: 3.3A

 

[Wheazel]

Will probably work just fine, I run a centrifugal clutch myself with a single smaller motor that weighs in under 1000g.
Id say the things to pay attention to in this setup is the gearing/driveline and the escs, thats where you will get trouble if any at all.
What gearbox are you planning to use? Some neugart 90degree angled or similar?
Also keep in mind the cooling of the motors if closed into a frame. The powerspecs are most likely overestimated and also for an airplane application with airflow.

 

[xadmx]

Will probably work just fine, I run a centrifugal clutch myself with a single smaller motor that weighs in under 1000g.
Id say the things to pay attention to in this setup is the gearing/driveline and the escs, thats where you will get trouble if any at all.
What gearbox are you planning to use? Some neugart 90degree angled or similar?
Also keep in mind the cooling of the motors if closed into a frame. The powerspecs are most likely overestimated and also for an airplane application with airflow.

hi
yes i was going to use a 90degree gearbox to try and keep it all in line with the frame, i don't no what ratio yet, i have a gearbox in my shed but i haven't had time to look what ratio it is. for the cooling i am thinking of putting a fan blade inbetween the motors that are joined together on the shaft. and one on the shaft on the top. and when i box the frame in i am thinking of putting a duct by the head tube. but i dont no if it will all work lol. i don't have a clue what escs yet i am still reading up on them.
adam

 

[gwhy!1]

I will just give you the heads up about using a clutch with your proposed setup ( assuming you are thinking about using a centrifugal clutch ) you will need a racing clutch at the very least if thinking about putting anywhere near even just 5kw through it, they get very hot very quickly, I fitted a standard clutch (£25i'sh) onto a quadard with only 3kw and the clutch last around 25mins of use so I upgraded to a racing clutch (£100i'sh) and so far its holding up with around 4kw after around 6 hours use ( the clutch will need to be setup for min slip time ).

 

[Whiplash]

I like how he has the clutch before any reduction takes place, should help it live...

 

[Wheazel]

The trick with the clutches are to change the springs so it engages 1:1 early.
When i bought my clutch it actually slipped at full throttle on a flat road. It was intended for higher rpms with the stock springs.
So i changed to the weakest springs i had at home, which are so weak they probably start to stretch at guesstimated 200rpm.
That doesnt mean the bike engages hard tho. The resistance from the mass getting into motion makes it to "slip as much as it needs" so to say.
If i go full throttle from almost a dead stop, the 1:1 is fast but not imminent and the front wheel gets very light and the motor pulls 3-4kw.

So in my case the motor is starting to feel torque at above 200rpm that grows with rpm. This a huge difference to having a 1:1 connection from 0rpm.
My clutch shows no signs of wear. I would not want to build sensorless without the centrifugal clutch based on my previous experiences with small rc motors.

 

[gwhy!1]

The trick with the clutches are to change the springs so it engages 1:1 early.
When i bought my clutch it actually slipped at full throttle on a flat road. It was intended for higher rpms with the stock springs.
So i changed to the weakest springs i had at home, which are so weak they probably start to stretch at guesstimated 200rpm.
That doesnt mean the bike engages hard tho. The resistance from the mass getting into motion makes it to "slip as much as it needs" so to say.
If i go full throttle from almost a dead stop, the 1:1 is fast but not imminent and the front wheel gets very light and the motor pulls 3-4kw.

So in my case the motor is starting to feel torque at above 200rpm that grows with rpm. This a huge difference to having a 1:1 connection from 0rpm.
My clutch shows no signs of wear. I would not want to build sensorless without the centrifugal clutch based on my previous experiences with small rc motors.

I removed the springs completely and it still slipped for to long with the really cheap clutch, maybe it was just the cheap clutch I used was really rubbish , but the racing one is fine ( still no springs ).

Edit: And it will make a difference on the dia of the clutch, I was using maybe a 3" clutch..

 

[Hillhater]

Edit: And it will make a difference on the dia of the clutch, I was using maybe a 3" clutch..

and the WEIGHT of the shoes will make the most difference.
Best clutches are the disc type used by kart racers..fully adjustable and repairable.

 

[Ratking]

I would not even try to build it like that, it takes too much space.
Unless you can live with a bulky large frame, where would your controller and batteries be?
I tried to design a frame like that, and I have two very good 90 degree gearboxes with the right reduction if you are interested.

The problem with this is;
Takes a lot of space
Gearbox with 90 degree drive is heavy and fragile
No good reason for doing it that way
High cg


Please don't take this as negative criticism, but from the above conclusion I don't see any feasible solution
doing it that way