Adrian Smith 1 Posted September 1, 2021 Share Posted September 1, 2021 Silly question. As somebody embarking on a motorised glider project after years of fixed wing stuff, I have selected a recommended motor with a 4mm shaft. Now I have in stock a suitable 11x7 Graupner folding propellor assembly from way back when which looks like it has a 5mm hole in the back plate, but I am not sure. Until I receive the motor to test it I won't know for sure so my question is if the fit is not right am I able to buy a suitable insert that will fit and where would I get it? I know I can buy another folding prop by JP with a 4mm hole, but that means spend another £20! Any suggestions. Thanks. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 1, 2021 Share Posted September 1, 2021 Got a mate with a lathe to turn up a sleeve? Thin tape wound round the shaft can give reasonably accurate location otherwise. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 1, 2021 Share Posted September 1, 2021 1 hour ago, Adrian Smith 1 said: Silly question. As somebody embarking on a motorised glider project after years of fixed wing stuff, I have selected a recommended motor with a 4mm shaft. Now I have in stock a suitable 11x7 Graupner folding propellor assembly from way back when which looks like it has a 5mm hole in the back plate, but I am not sure. Until I receive the motor to test it I won't know for sure so my question is if the fit is not right am I able to buy a suitable insert that will fit and where would I get it? I know I can buy another folding prop by JP with a 4mm hole, but that means spend another £20! Any suggestions. Thanks. Depends upon the design of the spinner, how it is attached to the backplate and how long the threaded portion needs to be to be able to take the prop yoke and nut. If the spinner is attached to the backplate with 2 screws, one on each side it's easier to find a driver: Prop drivers If it is attached to the backplate with a single screw through the centre its a bit more difficult. You may have to bite the bullet and go for a new spinner prop driver and yoke: Spinners etc What motor have you ordered? Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 1, 2021 Share Posted September 1, 2021 Also, what diameter spinner do you have (or need)? Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 Sadly, Martin I don't. Certainly tape might do it. I thought maybe insulating tape might do it if necessary. Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 https://www.overlander.co.uk/rc-motors/3536-08-1050kv-tornado-thumper-v3-brushless-outrunner-rc-motor.html Hi Shaun, the link is above for the motor. It's requires a 38mm spinner with 4mm shaft. I am trying to find a picture of the Graupner prop assembly I have, but it's probably not produced now. the spinner is attached to the back plate with two screws through the prop blades and another screw through the hub into the driver. The JP assembly I might have to plump for I will find a link. Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 The JP one I might have to buy is https://www.gliders.uk.com/JP-11x8-Folding-Propeller-With-38mm-CNC-Aluminium-Spinner/productinfo/JP4406020/ Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 I might have to buy this https://www.gliders.uk.com/Prop-ADAPTER-M8-for-4mm-shaft-Total-length-35mm/productinfo/AERO7124.44/ but will need to measure the length of the shaft and check if an M8 is right to see if it's straight swap, but as you say Shaun I may have to bite the bullet Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 1, 2021 Share Posted September 1, 2021 9 minutes ago, Adrian Smith 1 said: https://www.overlander.co.uk/rc-motors/3536-08-1050kv-tornado-thumper-v3-brushless-outrunner-rc-motor.html Hi Shaun, the link is above for the motor. It's requires a 38mm spinner with 4mm shaft. I am trying to find a picture of the Graupner prop assembly I have, but it's probably not produced now. the spinner is attached to the back plate with two screws through the prop blades and another screw through the hub into the driver. The JP assembly I might have to plump for I will find a link. What battery do you propose to use, 2S, 3S or 4S? Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 I might have to buy this https://www.gliders.uk.com/Prop-ADAPTER-M8-for-4mm-shaft-Total-length-35mm/productinfo/AERO7124.44/ but will need to measure the length of the shaft and check if an M8 is right to see if it's straight swap, but as you say Shaun I may have to bite the bullet Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 https://www.gliders.uk.com/ASK-21-Scale-Electric-Glider-KLW-Version-26m-Fibreglass/productinfo/FF-B018-E/ the recommendation for this is a 4S 2200 mAh which is what I am aiming at. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 1, 2021 Share Posted September 1, 2021 (edited) 14 minutes ago, Adrian Smith 1 said: https://www.gliders.uk.com/ASK-21-Scale-Electric-Glider-KLW-Version-26m-Fibreglass/productinfo/FF-B018-E/ the recommendation for this is a 4S 2200 mAh which is what I am aiming at. OK, there's an error on the page, the 3S prop should be 11x7, the 4S should be a 10x6. I have run the numbers through eCalc and I reckon that a 4S battery with an 11x7 will pull between 40 and 45 amps which is beyond the max for the motor. Run it on a 3S and it should draw around 30 amps which would be OK, drop it to 10x6 with a 4S and it should draw between 30 and 35 amps which would be fine too. The 4S option gives a thrust:weight ratio of around 1.2:1, the 3S around 1:1. These figures are at WOT of course. Hope this helps. Edited September 1, 2021 by Shaun Walsh Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 1, 2021 Share Posted September 1, 2021 If you already have 4S batteries go the 10x6 option, if not the 3S and 11x7 option is more economical as 3S batteries are somewhat cheaper (you may know this already?) Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 1, 2021 Author Share Posted September 1, 2021 Thanks for your feedback Shaun. I have not bought any lipos yet so no harm done. My folding prop that I already possss it at the workshop so I will take a picture of it and post it when I can get down there. Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 2, 2021 Author Share Posted September 2, 2021 Here are a few picture of the Graupner prop assembly. I was able to slot an M5 bolt in the hole which was a snug fit. An M4 was too small therefore I assume the motor shaft needs to be 5mm? The length of the insert appears to be 28mm so I guess a 26mm would fit. The diameter of the insert appears to be 9.9mm which puzzles me because the JP ones for a 4mm shaft are listed as M8. I am easily confused which is why I will probably buy a new assembly, but I don't like wasting stuff if it can be used! Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 2, 2021 Share Posted September 2, 2021 If that prop/spinner is old I would probably bin it, you've spent £200+ on a model I wouldn't risk the plastic yoke or the blade root breaking up and the subsequent vibration wreaking havoc with the front end of the model. I would replace the lot with a assembly using an aluminium yoke and backplate. Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 2, 2021 Author Share Posted September 2, 2021 Yes, Shaun. I must admit my first instinct is to avoid unreliable or unwise "fixes' such as tape around the shaft. Therefore rather than "spoil the ship for happeth of tar" I think I will buy new and bin the old one. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 2, 2021 Share Posted September 2, 2021 Ah - I assumed you were fixing a prop to a shaft and it simply required centring - I certainly wouldn't have recommended tape for a split collet adapter! Quote Link to comment Share on other sites More sharing options...
Christopher Wolfe Posted September 3, 2021 Share Posted September 3, 2021 To increase prop shaft diameter to fit a prop with a slightly larger hole I found that heat shrink tubing is quite useful. Use a few layers as required to snug the prop. It's quite concentric and easy to remove. chris 1 Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted September 3, 2021 Author Share Posted September 3, 2021 I will bear it in mind thanks, Christopher. Hopefully I shouldn't need to on this project. Quote Link to comment Share on other sites More sharing options...
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