I would like to use a RP5 chassis to mount an approximate 2-3lb load. I gather from a previous thread that it is likely that a 2lb load will not cause problems with driving the chassis, so I am not too concerned with operating the vehicle on the flat. However, the application I intend on using this for means that the vehicle will need to be able to drive up 30 degree slopes (possibly up to 45, but that’s not essential). Does anyone have any experience of testing this chassis on sloping ground, and if so, please could you let me know how well it performs?
In addition to this, I would like to get some more information on the internal geometry of the chassis. Is there a CAD model available that you could send me?
Any help or advice would be much appreciated.
We do not have any drawings or models of the chassis that are not on the web site. I think 3 pounds is generally going to be pushing the limits of the RP5 even without the slopes involved, and I think 45 degrees is unlikely even unloaded, though it will depend on the details of the surface you are trying to climb. 30 degrees is probably more doable, but there’s still the surface dependence, and I don’t think it would work very well even with 2 pounds.
We were driving the RP5 chassis around the office unloaded and it managed to climb up very steep inclines as long as it was on a high-friction surface. If your surface provides enough friction, you can get it to do 45 degrees when loaded with just the batteries and a light motor controller.
Jan was skeptical of my 45 degree claim, so we put the chassis unpowered and without batteries on a 45 degree plane and it slid down.
Thanks for trying this out for me - I think we need to balance the weight of the vehicle so that it will be light enough to drive up a steep slope, and heavy enough to provide enough traction to prevent it from sliding down again! I think we’ll get hold of one and do some testing ourselves, and I will let you know the outcome!
Just so you don’t waste too much time with unrealistic expectations, the weight of the vehicle doesn’t really matter. You might be able to get some very minor performance variations by messing with the distribution of the weight (e.g. don’t make the center of mass high).
I am currently doing some actual measurements of the RP5 with a vernier, including diameters and tread length, centre to centre measurements,
motor and gear ratio/speeds. I didnt consider loading, but i just might test it with a some loading.
I will post up the information when I have finished the calculations. I had similar questions too which I decided to test for myself.
Does anyone know the approximate/actual RPM of these RP5 motors at the motor output shaft side? I will try to work it backwards from the 15cm/s
spec and gear ratios. Is 11,000 RPM about right ?
If intending to use on grass or bare ground (dirt, sand, dust), then you might want to silicone seal all the joints (inside suface) on the bottom (below the battery pack) and the little holes on the side. When I tested mine on a grassy hill, I was amazed to see how much grass got in, and where it ended up in
a relatively short time.
We don’t have the spec, but 11,000 RPM sounds reasonable.
Thanks for doing these tests and measurements. I’m sure a lot of people on this forum will be interested in the results.
In terms of presenting the information, are you happy with scanned in hand calculations and dimension mark ups (neat off course!)
Or are you expecting something that is type written with electronic/photo graphics.
I may not do the load testing, because I dont have the means to accurately measure articles under the 1kg mark.
Since this is something you volunteered to provide, I’d be happy with just about anything.
Please find attached excel spreadsheet (Excel 2007).
I have summarised all calculations in the form of input and output cells.
Anyone who is interested in changing motors, gears, wheels on this platform
can experiment by changing the design parameters, and the spreadsheet will be
able to calculated anticipated speed. Making the actual physical changes is left to the hobbyist.
In terms of load bearing. Up to 1.3kg is fine for level floors, as long as the weight is
equally distributed. Going uphill is a different story as the battery can be depleted much
more quickly than anticipated.
I have not locked the spreadsheet, so anyone can feel free to add to it and contribute.
CAD file is in the making, hopefully by next week I can have something posted up.
Thanks again for your help and clarifications
RP5 speed calculation.xlsx (12.4 KB)
Your help is also much appreciated.