Motors

[P. H. StonesParticipant @p-h-stones25207]

An acquaintance has a 57" long S-Boat driven by a single Torpedo 850 brushed motor and 50mm prop using a 25amp ESC. I have a similar model but with three 40mm props. I would like suggestions for three smaller brushed motors producing roughly identical performance to the 850 which is excellent. I could of course install a single motor and retain the other two props & shafts as dummies but would prefer to use them.

Thanks

[P. H. StonesParticipant @p-h-stones25207]

S-Boat

[ashley needhamParticipant @ashleyneedham69188]

PH. This is a tricky one, as 40mm props are largish for high speed work and a 700 size motor may be required, three of these I am guessing without having looked up anything will be fairly heavy compared to one 850, and take up room …although I dare say you have sufficient room with a boat that big.

OR something like a 700 on the centre shaft and a pair of 555 on the outer to spin them might be an alternative. OR there again, three 850s would do the job, as the props are much smaller they would rev out and not draw their full current..they would easily spin these props and run forever with no heating issues and are reasonably priced.

Need someone who has actually used three motors really to advise.

Unless you dipped a toe in the murky waters of BRUSHLESS MOTORS…..a 1000Kv set might be good on 12v..but will need three ESC to suite three motors…

Ashley

[P. H. StonesParticipant @p-h-stones25207]

Thanks for that Ashley. I should add that I have in fact been using three OR brushless motors which do not constitute a problem as the boat runs well on them but the three matching ESC's tend to make everything a bit messy, making it difficult to get three NIMH batteries as well as the receiver and other items to fit in a tidy manner. Presumably it would be possible to use just one ESC but this might require more wiring by way of Y leads. My thinking therefore is to fit everything neatly by reverting to brushed motors and a suitable ESC which would still necessitate at least one Y lead but it would all become more compact. Referring to your suggestions, I do have a couple of 555 motors which I think require coupling inserts of 3.25mm and the nearest I have seen are 3.2mm. A 700 size centre motor is available quite cheaply so no problem there if I choose that route. Finally, I envisage the use of a 12v 9ah lead acid battery to run all motors and this would fit once enough room is made but would it cause any problems from a power angle?

[Malcolm FraryParticipant @malcolmfrary95515]

If looking for performance, dump the SLA. Get the same mAH in anything else at the same voltage and enjoy the weight saving.

[ashley needhamParticipant @ashleyneedham69188]

As Malcolm says, a Nimh is the way to go. As to the rest of the motor thing, it is a bit trial and error, unfortunately, we really need someone to post as to who is running a similar size hull with thro brushed motors.

I changed to Nimh batts on my Fantome (48 inches long) with twin 800`s and there is a noticeable difference in performance simply due to the lesser weight.

Ashley

[P. H. StonesParticipant @p-h-stones25207]

The weight of a 12v 9Ah lead acid battery is 2.6Kg compared with 1.47Kg for NIMH batteries with identical specs so it obviously makes sense to use the latter. On the debit side however is the cost with the NIMH being around £102 so it seems a question of 'what price performance?' and that's something I'll have to consider and would I need a new charger? Now, as I mentioned earlier I do have 555 motors from Model Motors Direct but no mounts and so far there has been no response to my e-mails. Is Mr Graham still in business? If not then I'll have to make my own but I would prefer not to. Contrary to my belief, the 700 motors seem to be rather scarce and it would be useful to learn of a supply source.

Thanks

Paddy

[P. H. StonesParticipant @p-h-stones25207]

In the absence of comments from anyone with a three motor S-Boat I have more or less decided to fit a Torpedo 850 and run the boat on that alone with an appropriate ESC of course. Removal of the two outer shafts and props appears necessary to avoid drag from non rotating props, meaning that the tubes will have to be sealed off, preferably so that they are easily opened up again should further changes be required. I imagine that drag from the vacant A brackets will be minimal and not affect performance much. The 850 apparently needs a 45mm or 50mm prop and due to lack of space only the former can be fitted but is a particular pitch essential? Any suggestions concerning that and for sealing the tubes would be of interest.

Paddy

[Trevor HollowayParticipant @trevorholloway99134]

For sealing the tubes I would remove the propand just put a locknut on the shaft. Re-fitting to three motors at a later date would beeasier.

As for which prop to use I would bow to the presence of greater knowledge than I.

[ashley needhamParticipant @ashleyneedham69188]

Paddy. An X pitch 45 prop would be best, or consider a brass 45mm prop to give the blade area. An 850 does not rev too much (9000 rpm) to overspeed a normal brass prop.

You could consider spinning the outer propshafts with a 555 or low drain 540 rather than having them as dummies, use a slightly smaller prop or an S pitch 45.

Trevors idea is the one..how easy !

Ashley

[Trevor HollowayParticipant @trevorholloway99134]

There's always an easy way – the hard part is finding it !

[P. H. StonesParticipant @p-h-stones25207]

Having considered the options so far, I think Trevor's suggestion of using locknuts is a sound one to follow and I'll do just that. I will install a single Torpedo 850, fit a 45mm Brass prop and two 12v NIMH 5aH batteries in parallel via an ACTION P103 with a 50amp ESC to complete the set up ( no, I won't forget a fuse!). The boat's performance should be satisfactory but that remains to be seen. Unless anyone thinks otherwise!! Fingers crossed.

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