Autopilot Torque Curves

[Tim Good]

Please can someone help me understand these charts for two autopilot motors I am considering. I am currently using option 1. It says it gives 2nm and 220RPM at the summary at the bottom. Option 2 is the same size motor but different ratings and says 8nm at 150RPM.

I am trying to relate that back to the charts which are confusing and suggests the 403.311 operates at either 225 or 275 RPM and not 150 as per the summary below. If it is opperating at that speed and has an 8nm operating torque then it would be a strong and better replacement to the 403.929 which I am using now.

Does anyone have experience working with these kind of documents?

Option 1: 403.929 (12v)

Option 2: 404.311 (12v)

 

[danielefua]

Please can someone help me understand these charts for two autopilot motors I am considering. I am currently using option 1. It says it gives 2nm and 220RPM at the summary at the bottom. Option 2 is the same size motor but different ratings and says 8nm at 150RPM.

I am trying to relate that back to the charts which are confusing and suggests the 403.311 operates at either 225 or 275 RPM

No. This is not true, in fact according to the graphs, 225 and 275 RPM are exactly the "no torque condition" i.e. free running - useless!

and not 150 as per the summary below.

This is indeed the ideal "working condition"

If it is opperating at that speed and has an 8nm operating torque then it would be a strong and better replacement to the 403.929 which I am using now.

Does anyone have experience working with these kind of documents?

You may be confused by the many curves appearing in the graphs. The downsloping ones are the "speed vs torque" curves and the vertical units to be considered are the RPM, the upsloping ones are the "ampere vs torque" curves and the vertical units to be considered are the ampere.
Moreover for each motor and each kind of curve there are two extreme curves with an index "max" and "min". The working curve must be considered half way.

Please notice that I am not an expert but this is what I understand and it does make sense.

Daniel

 

[Tim Good]

Thanks.. So based on that, everything tells me you're getting a bit more Umph out of the 404.411 at the same rpm or amps?

Is that what you see?

 

[danielefua]

If by Umph you mean torque, it seems so but the difference looks almost negligible and it makes me wonder if it is real indeed.

Daniel

 

[Tim Good]

Umph = torque yeah I did manage to find this also which shows the same 404.311 curve but based on the Min.

Using that to compare:

403.929 - @150rpm is does 4nm
404.311 - @150rpm is does 6.2nm

403.929 - @80rpm is does 8nm
403.311 - @150rpm is does 11nm

That seems like a reasonable amount more no? That is if I am reading it right.

(Edit* Second 403.11 should read 80RPM)

 

[danielefua]

I agree, what you wrote is right apart from an obvious typo: "150rpm" instead of "80rpm". Overall the 404.311 seems to have 1) a higher idle speed (at no torque) and 2) a higher Max Torque (at zero speed). This implies that the motor is more powerful indeed.

I would like to add that the matter is far from clear because in a document I found that the 404.311 is also rated 2 Nm (Nenndrehmoment=Rated Torque). Moreover I do not understand how to compare correctly the two curves n_min and n-max given for the 403.929 with the unique curve given for the 404.311.

Do you know which is the torque required by your autopilot? Are you fitting an additional reducing gearbox?

Daniel

 

[Tim Good]

Do you know which is the torque required by your autopilot? Are you fitting an additional reducing gearbox?

I already have the 403.929 but its is 1996 original and playing up. I was going to replace like for like but the saw the 404.311 which is half the price and seems to be a slight more powerful. I assume the 403 is pricey as it is no obsolete and not many around maybe. My pedestal has a lot of reducing gears and assuming that Whitlock specificed the 403.929 originally.

I don't know if will work as I never saw the AP working when I bought the boat. I'll order a 403.311 and report back once it is in and steering the boat