I had the a75hd until I parted it out and made other quads with it . I thought it flew well enough but was definitely heavy for its size. I wasn't doing anything more than cruising around though, so not sure how it would perform flying freestyle acro. Decasing the vista would help I'm sure.

(02-Aug-2023, 08:10 AM)dwije21 Wrote: Thanks so much! Curious, if I use 4 blade prop instead of 3 blade can I do the following math (assuming pitch is the same) -

93 / 3 blades = 31 * 4 blades = 124g for a 4 blade prop of eqivalent pitch? (There's a 1636 by 4 blade vs the 1635 by 3 blade it comes with). That would be closer to a 5:1 ratio.

Or is that too simplistic to estimate thrust without a thrust stand?

Also let me know what you think of trying 4S instead of 3S.

I’m by no means an expert, and I’m often wrong, but I think that’s a bit too simplistic. 
By increasing the blade count, I’d expect it to change multiple other factors- increase drag, potentially decrease rpm in real life, decrease efficiency, increase amp draw, etc.
The increase in drag, lots of other potential airflow related things that are beyond my comprehension, and the potential decrease in rpm would be the things I’d expect to effect thrust made or lost.

I’m including a little snippet of a different motor data sheet below. This isn’t for your motors, this is from some 1002 14000kv, but, it shows the measured thrust for 1635 tri-blades vs 1635 quad-blades on this specific motor. I’m just using it as an example to illustrate the point.
Using your math, with the GF1635*3 (1635 tri-blades):
92g thrust, so, 92 / 3 = 30.67
So you’d expect the 1635 quad blades to make 30.67g * 4 = 122.67g thrust.
But…
With the GF1635*4 (1635 quad-blades) it’s only making 98g thrust.


You’ll get an increase in thrust with quad-blades vs tri-blades of the same pitch, but I couldn’t tell you how much without running all the numbers through eCalc.

As far as 4s goes, I would expect those motors to burn out on 4s without a motor output limit. With the additional weight of another battery cell combined with the needed output limit on the motors, I think you’d cancel out any gains you may get from running them higher than 3s voltage.

(02-Aug-2023, 08:20 PM)Lemonyleprosy Wrote: I’m by no means an expert, and I’m often wrong, but I think that’s a bit too simplistic. 
By increasing the blade count, I’d expect it to change multiple other factors- increase drag, potentially decrease rpm in real life, decrease efficiency, increase amp draw, etc.
The increase in drag, lots of other potential airflow related things that are beyond my comprehension, and the potential decrease in rpm would be the things I’d expect to effect thrust made or lost.

I’m including a little snippet of a different motor data sheet below. This isn’t for your motors, this is from some 1002 14000kv, but, it shows the measured thrust for 1635 tri-blades vs 1635 quad-blades on this specific motor. I’m just using it as an example to illustrate the point.
Using your math, with the GF1635*3 (1635 tri-blades):
92g thrust, so, 92 / 3 = 30.67
So you’d expect the 1635 quad blades to make 30.67g * 4 = 122.67g thrust.
But…
With the GF1635*4 (1635 quad-blades) it’s only making 98g thrust.


You’ll get an increase in thrust with quad-blades vs tri-blades of the same pitch, but I couldn’t tell you how much without running all the numbers through eCalc.

As far as 4s goes, I would expect those motors to burn out on 4s without a motor output limit. With the additional weight of another battery cell combined with the needed output limit on the motors, I think you’d cancel out any gains you may get from running them higher than 3s voltage.

That's super helpful. Thanks for the sound reasoning.

Interestingly someone did try 4S on this quad. I'm scared but curious. I did get 350mah 4S HV so technically it's lighter than the 450mah 3S by 4grams. Probably will be real short flight but will be interesting.

Well I appreciate everyone's input here. I think that I'm going to return the A75 and get the BDI digiadapter, a tbs fusion, and a mobula 6 with 30000kv motors and the biblades. Seems like it's my best option.

I was wary because of the analog and I didn't want to buy new goggles or have the added latency of the BDI but this seems like the best compromise and ends up being similarly priced to a HD DJI A75.

(02-Aug-2023, 02:06 AM)dwije21 Wrote: Oh wow. I guess I'm not used to thus weight class at all. Crazy. Well I'll give it a go and see. If anyone has experience with the A75 let me know.

Engaging blunt mode...................  

YES, do as per your last post!

Indoor flying at home is an area where 5g difference upwards can make a large difference in ability and comfort.

The A75 (which I owned briefly before sense prevailed, I commented on it briefly in another post of yours) is FAR too overweight for true "indoor" use, even cruising use, you can forget comfortable indoor freestyle. Its not a power thing at all, more power will not help.  Its 67g without a battery, and going 4S and more powerful motors is chasing completely the wrong way.  HALVE that total weight and you are talking. Achievable with that frame, etc?  NO.

We don't know how big your "indoors" is, but I can assure that unless you have a sports hall space, even basic flips in Horizon mode will be fraught with risk. We don't know your true piloting skill level in acro either, but I'm no beginner and I have a lot of craft. DJI, HDZero, and Analogue.  Approaching 100g is going to damage things!  It'll always be on a knife edge, ready to stab off in a direction you do not want at a speed beyond that safe for the space. Just leads to frustration and no learning.

I would not go there with a DJI HD A75, its like trying to use a large SUV on a go kart track, barely possible if at all and never going to be capable of what it should be, no fun. Mine was bought for garden use in a (for the UK) sizeable space.  It didn't go well even for that.

Look at starting with the Mobula6 analogue, or if your space allows the Moblite7, and put an analogue receiver on your goggles or buy a cheap headset like the Eachine 800.  You'll save your furnishings, injury and your nerves, and it'll be a much more capable and effective learning tool.

(06-Aug-2023, 04:45 AM)dwije21 Wrote: I was wary because of the analog and I didn't want to buy new goggles or have the added latency of the BDI but this seems like the best compromise and ends up being similarly priced to a HD DJI A75.

I fly analogue and HDZero HD indoors in a two story all brick home. With either I can be three brick walls away with the quad AND 80 feet down a garden.

Not used analog on the DJI goggles I have, I use Eachine EV200D. Do have a wide range of various budget headsets and goggles, and the Eachine EV800D headset is an adequate (and cheap) product, with no latency issues.

(06-Aug-2023, 06:42 AM)Bad Raven Wrote: Engaging blunt mode...................  

YES, do as per your last post!

Indoor flying at home is an area where 5g difference upwards can make a large difference in ability and comfort.

The A75 (which I owned briefly before sense prevailed, I commented on it briefly in another post of yours) is FAR too overweight for true "indoor" use, even cruising use, you can forget comfortable indoor freestyle. Its not a power thing at all, more power will not help.  Its 67g without a battery, and going 4S and more powerful motors is chasing completely the wrong way.  HALVE that total weight and you are talking. Achievable with that frame, etc?  NO.

We don't know how big your "indoors" is, but I can assure that unless you have a sports hall space, even basic flips in Horizon mode will be fraught with risk. We don't know your true piloting skill level in acro either, but I'm no beginner and I have a lot of craft. DJI, HDZero, and Analogue.  Approaching 100g is going to damage things!  It'll always be on a knife edge, ready to stab off in a direction you do not want at a speed beyond that safe for the space. Just leads to frustration and no learning.

I would not go there with a DJI HD A75, its like trying to use a large SUV on a go kart track, barely possible if at all and never going to be capable of what it should be, no fun. Mine was bought for garden use in a (for the UK) sizeable space.  It didn't go well even for that.

Look at starting with the Mobula6 analogue, or if your space allows the Moblite7, and put an analogue receiver on your goggles or buy a cheap headset like the Eachine 800.  You'll save your furnishings, injury and your nerves, and it'll be a much more capable and effective learning tool.

Thanks. Yeah it's hard to accept going back on digital but ultimately I want something that closely approximates a 5" quad indoors and by all counts the mobula 6 analog with high kv motors is the only way to do this.

The extra latency using the digiadapter doesn't seem to be an issue. It's an extra 10ms for perhaps 30ms total. My DJI v2 system is 27ms (best case) at its best and it feels locked in enough for my skills. I doubt I'd notice 30ms. Also folks complain about the blackout of the AV input when signal breaks up but this has been fixed by using NTSC instead of PAL is my understanding. So I don't see much of a downside.

If down the line I want to upgrade to dedicated analog goggles then I can and only have to get goggles since I already would own the fusion etc...

Let me know if I'm crazy here with approach. I just can't stomach buying all this stuff and a pair of orqas and I don't want to get a budget goggle or box goggle.

(06-Aug-2023, 01:26 PM)dwije21 Wrote: Also folks complain about the blackout of the AV input when signal breaks up but this has been fixed by using NTSC instead of PAL is my understanding. So I don't see much of a downside.

If your googles are rooted you can install the "avin-mods" WTFOS package which is said to resolve/fix the issue with PAL cameras. I don't run an analog module on my DJI FPV Goggles so I can't personally verify if that is actually true or not.

(06-Aug-2023, 05:33 PM)SnowLeopardFPV Wrote: If your googles are rooted you can install the "avin-mods" WTFOS package which is said to resolve/fix the issue with PAL cameras. I don't run an analog module on my DJI FPV Goggles so I can't personally verify if that is actually true or not.

Oh cool! I do have WTFOS and didn't realize that was a mod. Awesome! Thanks Snow