martynwakeman
07-04-2003, 08:57 AM
Hi,
I am looking for an electric motor solution to power a scale motor torpedo boat (deep V hull) --- VosperThornycroft Perkasa. Picture attached is of a Tamiya model. The real boat would run at 50 knots from 3x gas turbine engines. The model is 5700g in weight, without batteries & motor & RC gear. Length = 1225mm, Width = 315mm. The current propeller is 55mm diameter and the largest that I could fit is 60mm diameter. It has a plain bearing prop shaft. I am looking for an electric power solution because the model took a long time to make and I don't want to loose it through an IC engine stalling a long way from the shore.
I have made a displacement test and have approx 4.5kg capacity for batteries and motor (e.g. if motor is 600g, batteries can be 3250g). A heavier version at 5450g of batteries was also tested, but the boat was heavy in the water and I guess may struggle to plane. Do you have a motor suggestion that will give approx 15minutes run time with a 3.2kg battery weight while giving planning performance? The model should be fast, but insane or dangerous to itself (melting of electronics!). The boat must be able to plane, with some conviction, but it does not need to empty the lake! The installation should be robust and give good motor life.
I have had the Plettenburg HP 355BM/37/5/EVO motors running straight suggested. This seems very powerful, but it is a big model.
Would a small HP355/25/6 be better???
From the currents that these draw (e.g. 30 to 60 amps depending on load), it looks like a short run time would result (e.g. 30amps from 9AH pack = 16 minutes (80% efficiency), 60amps from 9AH pack = 8 minutes)? What current would a motor typically draw if the min and max is 30 and 60 amps when running a propellor? When should one use a reduction gear box on the motor? Is it better for the motor to use 24V or 36V ...
Batteries:
Do I need to make up 2x 36V packs, or could I couple together say 4 or 6 12V packs (so I can use them in land models)
With NiCad this could be:
- 24V at 4AH, 2208g
- 24V at 8AH, 4416g (heavy)
- 36V at 4AH, 3312g
With LeadAcid:
- 24V at 7.2AH, 4940g (heavy, but so different from 24V 8AH NiCad, and much cheaper!)
NiMh seem to be very fussy regarding maintainance and charging and I will only use the boat occasionally.
Is the Schulze mcc1010-80-ro a suitable speed controller?
Any suggestions would be very welcome, as I am trying to choose the best motor and battery combination.
Martyn Wakeman
I am looking for an electric motor solution to power a scale motor torpedo boat (deep V hull) --- VosperThornycroft Perkasa. Picture attached is of a Tamiya model. The real boat would run at 50 knots from 3x gas turbine engines. The model is 5700g in weight, without batteries & motor & RC gear. Length = 1225mm, Width = 315mm. The current propeller is 55mm diameter and the largest that I could fit is 60mm diameter. It has a plain bearing prop shaft. I am looking for an electric power solution because the model took a long time to make and I don't want to loose it through an IC engine stalling a long way from the shore.
I have made a displacement test and have approx 4.5kg capacity for batteries and motor (e.g. if motor is 600g, batteries can be 3250g). A heavier version at 5450g of batteries was also tested, but the boat was heavy in the water and I guess may struggle to plane. Do you have a motor suggestion that will give approx 15minutes run time with a 3.2kg battery weight while giving planning performance? The model should be fast, but insane or dangerous to itself (melting of electronics!). The boat must be able to plane, with some conviction, but it does not need to empty the lake! The installation should be robust and give good motor life.
I have had the Plettenburg HP 355BM/37/5/EVO motors running straight suggested. This seems very powerful, but it is a big model.
Would a small HP355/25/6 be better???
From the currents that these draw (e.g. 30 to 60 amps depending on load), it looks like a short run time would result (e.g. 30amps from 9AH pack = 16 minutes (80% efficiency), 60amps from 9AH pack = 8 minutes)? What current would a motor typically draw if the min and max is 30 and 60 amps when running a propellor? When should one use a reduction gear box on the motor? Is it better for the motor to use 24V or 36V ...
Batteries:
Do I need to make up 2x 36V packs, or could I couple together say 4 or 6 12V packs (so I can use them in land models)
With NiCad this could be:
- 24V at 4AH, 2208g
- 24V at 8AH, 4416g (heavy)
- 36V at 4AH, 3312g
With LeadAcid:
- 24V at 7.2AH, 4940g (heavy, but so different from 24V 8AH NiCad, and much cheaper!)
NiMh seem to be very fussy regarding maintainance and charging and I will only use the boat occasionally.
Is the Schulze mcc1010-80-ro a suitable speed controller?
Any suggestions would be very welcome, as I am trying to choose the best motor and battery combination.
Martyn Wakeman