# How to investigate pulleys and belt

1. Feb 26, 2016

### Raine Hooke

Hi. Me and my team are re-building a human powered aircraft's transmission system, and are currently designing the part of the pulley and belt. We've bought the belt and pulley quite some time ago from different shops, thus, we now have to re-investigate whether the pulley and the belt match perfectly, and wish to investigate them in terms of efficiency and all the calculations involve, to ensure it can be performed at the best condition. All the details we have about them are merely the belt's code, which is "16T10/2800 PAZ Z045 408878" from BRECOFLEX company, and it was made in Germany. Does anyone able to give a hint on how can we find out more details and information about it, and how should we investigate it? Your advice and assistance will be very much appreciated. Thanks in advance!

2. Feb 26, 2016

### Nidum

http://www.brecoflex.com/

I don't quite understand the problem . The Brecoflex site has encyclopedias of information on it and online calculators .

If you have a specific question please come back .

3. Feb 26, 2016

### Nidum

Detailed evaluation would be needed but possibly a light series PolyV belt would be a better choice .

4. Feb 26, 2016

### Raine Hooke

Thank you for your reply Nidum! My main problem now is that we're looking for ways to investigate the performance of the pulley, as it was a human powered aircraft, we need a really efficient transmission system. We currently have aluminium pulleys bought from another shop matched with the belt, but we might consider to change them to a 3D printed plastic pulleys to reduce the weight. We wonder how can we maximize the performance of this system, meanwhile making sure that it operates under a safe condition, which is always an important factor in engineering design. This is why we were thinking to find out details about the belt, such as its' Young Modulus, strain, elastic limit, etc.

5. Feb 26, 2016

### gjonesy

In other words you need maximum output RPM with minimum input RPM this would suggest you seek the optimum pulley ratio combination? I would suggest you do some testing for your setup. You need a tachometer. http://www.gaugecity.com/p-112-digital-tachometer-eht-600.aspx, assuming its (prop driven) you need a device to measure wind speed output velocity, LCD Anemometer Wind Speed Meter Air Flow will do, http://www.walmart.com/ip/49312694?wmlspartner=wmtlabs, You also need minimum sheer and wind resistance. Your entire design should also incorporate a factor for minimum drag force and maximum lifting force along with your power to weight calculations. An optimum set up would be a R1 (revolution) input =R2 (as many turns as humanly possible) output. SO for every one turn of your input pulley you want =R2? revolutions of your output pulley. And only you can determine this.

edit: R1 = RPM of Driver - R2 = RPM of Driven
http://culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html

Last edited: Feb 26, 2016
6. Feb 27, 2016

### CWatters

If you want to measure the efficiency of the transmission I think you will have to set it up on a test jig and measure power in an out.

7. Feb 29, 2016

### Raine Hooke

Wow! Thanks a lot for your detailed explanation, gjonesy! But we have already done all the calculations part, since the aircraft had been started to build since 2 years ago, but never success in taking off. We had been divided into groups to focus on improving different parts, and this is why I wanted to find out the "belt and pulley relationship", in order to judge whether should we change the pulleys we are currently using or not.

8. Feb 29, 2016

### Raine Hooke

Hi CWatters, thanks for your suggestion! We had been carrying out a lot of testing throughout the building process, and we just thought of is there any other approach we can do before carry out the physically testing to maximize the chances of getting the positive outcome we were expected.

9. Mar 1, 2016

### gjonesy

Nidum is right , you'd have to post some detailed drawings and possibly some photos of what you are working with for the best help possible with this. I'd include all measurements and a description of all the problems encountered during your testing/ prototyping. and you are on the right track with making it light as possible. 3d printing the pulleys is an excellent idea provided its strong enough for its application.

10. Mar 1, 2016

### CWatters

Have you looked at the transmission system used on other successful man powered aircraft? I'm sure some of them will have published data on the efficiency of their transmission. Then you need to measure yours to see if it's better or worse. If worse then you immediately have a possible solution. If better then perhaps no need to waste time improving it, better to put the effort in elsewhere. If you think testing is a waste of time ask yourself... How will I know if my new design is an improvement or not?

PS I don't mean test it by trying to fly. I mean test it in a jig. Set up instruments to measure the performance and calculate the efficiency.