Hi all, some time since I last had my Spitfire on the bench. I bought a Hobbyking O/B motor without Brushless, to save some money. I now find that the shaft is 3.9mm diameter, but there are no propellors that will fit that size. Has anyone else had that problem

Cheers,
Martin

Hi,
we all use 4mm drive dog propellers. I never measured whether it was 4mm or 3.98mm

But your store shows only 3.18mm (1/8th"). So, can I buy a prop from you?

Martin

Kneeler schrieb:
Hi Martin,

Are you sure you mesured the shaft correctly? As far as I know all of the HK ourboards use a 3.18mm shaft for the propeller. The part of the shaft that slides into the bearings inside the motor is 4mm, but the prop stumb is 3.18mm

If it realy is 3.9 on your calipers you could simply use a prop for a 4mm shaft, that's no problem.

Hi Lex,
yes I know how to use calipers! It is definitely the shaft as it ends in an M4 thread with a blue anodized Nylok nut. It is a short length of 3.95mm shaft with a dog drive on it.
Your parts store only shows bronze propellors with 2 sizes and both are 1/8th " drive.

Where can I can get 4mm drive props?

Martin

Here there are som props for 4mm shafts www.tfl-hobby.de/Propeller/Bronze/2-Blatt/ but they start from 35mm upward. I run the 35mm one with a 2500KV motor, that performes great.

Or you could check out OSE, they cary tons of propellers. Mostly inch size shafts, but some in 4mm. They also have the TFL props these days : www.offshoreelectrics.com/products.php?c...FL+Racing+Propellers

Props for 4mm shafts in small sizes, 30 to 35mm, are hard to come by. Teh best option might be to machine the shaft down to 3.18mm. That way there are far more props available for yout outboard. But you need machine bench for that, or a friend with acces to one.

You could also consider drilling out the thread on a M4 prop. That way you could use the Graupner props, but you need to have the equipment to do so. Although its a brass thread, so if you first drill with 3,5mm and that 4mm it could be done by hand, letting the drill find its own way.

Last option is to get a new propshaft 4mm to 3.18 and glue that on to a length of flex shaft to make new one. www.tfl-hobby.de/Antrieb/Aussenborder/au...rop--Sicherung-.html


PS, no insult intended with that caliper remark of mine. I have no idea about your mechanical skills, and you would be supprised of the number of people hwo have trouble taking good measurements.

Hi Lex,
no offence taken. I guess there are more and more people today who are pretty useless all round! I only have to look at my grandchildren to prove that.

I found a CNC aluminium 32mm prop here thanks to a guy on R/C Groups forum:-https://www.ebay.co.uk/itm/2-blade-left-rotation-CNC-Aluminum-alloy-propeller-prop-4mm-shaft-rc-boat-1670/122516129087?hash=item1c8687c53f:m:md9goEFTbcTPeUBPWI5utaQ

Cheers, Martin

PS, my Spitfire is coming on nicely again. I shall never race it, but will show it in Britain when I attend meetings to try and popularise 152VO.