FT Goblin - Prop troubles

[Duck]

The nylon washers I had laying around were too large so I bought a small set of metric nylon washers. The m5 are a perfect fit and two of them allow the prop to clear the bell without rocking. These should be perfect. I'll have a whole range of APC props to try now. I'll report back on the performance. If I get a chance I'll also run them through my amp meter on the bench to get amp draw numbers. Lets all hope the magic smoke stays away.

 

[Hai-Lee]

The nylon washers I had laying around were too large so I bought a small set of metric nylon washers. The m5 are a perfect fit and two of them allow the prop to clear the bell without rocking. These should be perfect. I'll have a whole range of APC props to try now. I'll report back on the performance. If I get a chance I'll also run them through my amp meter on the bench to get amp draw numbers. Lets all hope the magic smoke stays away.

When using a number of plastic or nylon spacers the friction between them can be quite low and the prop can spin at a different speed to the motor. If forced to use plastic spacers I usually add a star washer between the prop and the plastic spacer so that the star bites into the prop and the plastic spacer thereby locking the prop to the motor output shaft very tightly.

Just what works for me!

Have fun!

 

[Duck]

When using a number of plastic or nylon spacers the friction between them can be quite low and the prop can spin at a different speed to the motor. If forced to use plastic spacers I usually add a star washer between the prop and the plastic spacer so that the star bites into the prop and the plastic spacer thereby locking the prop to the motor output shaft very tightly.

Just what works for me!

Have fun!

Interesting! Is this needed with a single washer?

 

[Hai-Lee]

Interesting! Is this needed with a single washer?

It all depends upon where the washer sits and the friction/knurled surface of the metal washer and the motor shaft mount for the prop.

In the past I have had a prop split at the hub whilst trying to make it tight enough to stopping slipping and another time the prop nut would come loose when the throttle was cut.

Using a single star washer bound the prop to the spacer which was in contact with the knurled surface of the prop mount on the motor and the prop was locked even with only moderate prop nut tension.

What worked for me!

have fun!

 

[Duck]

Results!

I got a chance to get to the field yesterday and try out the new props. I didn't have any star washers, but more on that later. I didn't get a perfect comparison as I didn't have two identical batteries. But I did get some results. I tried the APC 5.1x4.5 with a 4S 1500mah pack (RDQ) and the 5x5 with a 4S 1800mah pack (RMRC). The 5x5 had noticeably less thrust but was also quite a bit faster. It struggled a bit more with vertical flight. On the battery difference, the 1500 pack is actually a better pack and on my normal prop gives better performance.

Like I mentioned, I didn't have any star washers. I just used 2x M5 nylon washers. The first fit inside the inset in the prop itself so the second was needed to actually increase the standoff. The 5.1x4.5 prop fully cleared the bell like this. The 5x5 did not! It actually fit between the spokes on the bell. I tightened both down as much as possible. But afterwards the 5x5 had dimples from the bell. It obviously had slipped in flight.

Cool validation of what @Hai-Lee said. I bet with it pressing on the motor bell itself, those dimples only represent pressure, not slippage. The 5.1x4.5 prop may have more it can give with an extra washer as nothing was keeping it from slipping. The prop nuts have slight ridges on the bottom but they are also rounded on the edge of each ridge (not sharp) so I wouldn't expect them to stop the prop slipping fully.

 

[Duck]

I think I can go a little faster. Time to build a new goblin for some head to head speed tests.

T-Motor's chart for this motor lists ~47A for 4S with a 6x4 prop. The battery should be able to handle it. I have a Cobra 60A esc if the finwing one gives me any issues. I've used them before and they are awesome. My last one got punctured due to pilot error so I am excited to have another in my box.

 

[Duck]

Alright, ready to give this a go. A new goblin has been made alive with the new ESC, motor and the same prop. I figured I can make a direct comparison to the other goblin. I can even put the same battery (RDQ 1500mah 4S) in both. The new one doesn't have FPV yet so the balance & weight is slightly different.

I also tried a little more paint masking after watching the most recent master series painting video with John Overstreet. It worked better and I only wound up with a tiny patch (like 2mm sq) with the paint lifted when I removed the masking tape. I determined I should use a much lighter sandpaper though. I was using 80 grit to make sure it stuck and the surface is really rough now even through the paint. Mostly it gave me nice clean lines.

Now I just have to wait for a chance to fly between weather and all other obligations.

 

[Duck]

Alright, ready to give this a go. A new goblin has been made alive with the new ESC, motor and the same prop. I figured I can make a direct comparison to the other goblin. I can even put the same battery (RDQ 1500mah 4S) in both. The new one doesn't have FPV yet so the balance & weight is slightly different.

View attachment 169171

I also tried a little more paint masking after watching the most recent master series painting video with John Overstreet. It worked better and I only wound up with a tiny patch (like 2mm sq) with the paint lifted when I removed the masking tape. I determined I should use a much lighter sandpaper though. I was using 80 grit to make sure it stuck and the surface is really rough now even through the paint. Mostly it gave me nice clean lines.

View attachment 169172

Now I just have to wait for a chance to fly between weather and all other obligations.

Wow that is fast! I tried it today and it is alot faster. It torque rolls like crazy though.

 

[BATTLEAXE]

Wow that is fast! I tried it today and it is alot faster. It torque rolls like crazy though.

No vid, didn't happen

 

[Duck]

No vid, didn't happen

The FPV setup is still not installed so there is no proof even from DVR. But it is intact and will fly again so we should be able to get something.

 

[BATTLEAXE]

The FPV setup is still not installed so there is no proof even from DVR. But it is intact and will fly again so we should be able to get something.

They are a quick nimble machines though aren't they