Category: PIETECH

PIETECH Volume 1, page 1: PIE 4.0 and PIE 2.0 Thrust Stall Test Results

 

 

 

PIETECH

As we open a new chapter in the PIE project previous chapters are not closed, instead they continue as the earliest pioneering efforts put forth leading to PIETECH and will undergo more extensive power in/out ratio testing for scientific purposes.

The PIE 1.0 & 2.0 are also the necessary “trainers” to teach the concepts of PIETECH, and actual building plans are forthcoming within the next few months!

Update added: The PIE 2.0 requires just over 30 oz of thrust to self-propel as seen in the earlier posted video. Another test was run, using weights placed in front of the PIE 2.0. The weights were added until it would not move them, then backed off until movement was just apparent. Then a digital scale was used to push the whole rig forward in order to determine maximum thrust (stall method). This test was repeated a total of 8 times with identical results.

Maximum thrust is now calculated at 230 oz which is 14.375 lbs or 6.52 kg.

Bryan-

PIE 3.0 is a hybrid design which has been which has some unique features which include an active RPM control system using offset pivots. The PIE 3.0 has thus far shown itself to have tremendous power potential but the early tests have proven internal stresses which are very difficult to contain. This 3.0 design is a collaborative effort being developed in a separate lab.

PIE 4.0 is a high-speed PIE designed to run well above the speeds of the PIE 1.0 & 2.0 and designed to explore the power of speed v. weight. Early designs have focused on increasing the mass of the weights, and has proven that increasing the mass is effective to a point but that increasing the speed has a much greater effect with very small incremental changes.

 

High-Speed Planetary Gears

The fist obstacle to a high-speed drive is the planetary gear set. While high speed spur gears are available commercially, the cost for these gears tends to be prohibitive for experimental use in which component damage is rather common.

The Planetary gears need to be able to smoothly run at speeds exceeding 1000 RPMs as well as run within reasonably acceptable noise levels.

1st Experimental Gear Set

The first experimental high-speed gears have been made with reinforced cloth covered flexible material from 14mm pitch industrial timing belts, and although this is very quiet, they flex too much and timing between gears is impossible to hold. This may be revisited another time but is not considered viable for experimental use right now.

 

2nd Experimental Gear Set

It has been decided (for now) to use chain sprockets for the planet gears and an inverted chain drive sun gear. The inverted chain drive is simply a sprocket with the teeth cut down about 90% of the way. A roller chain is wrapped onto the gear and the divots formed at the bottom of the teeth hold the chain so it cannot slip. The chain ends are connected with a standard connector and has not had any need for further work or welding so far.

The only problem experienced with this has been that of run-out due to the sun gear axle getting bent slightly and the deflection of the flexplate. The (possible) solution to those issues has been worked out and will be reported here when it is unveiled.

 

The PIE 4.0

The new PIE 4.0 has now been bench run. It uses very low mass (1.94oz) weights and a 110 volt motor to spin it. The RPM tested at this point is 850 (+/- 10 RPMs).

The high RPM certainly does make a difference, as the PIE proceeded to dump the bench and its contents the 1st time and then with the 2nd run (which was videoed) it pulled itself out of the c-clamp holding it to the bench. That is a lot more power than was anticipated.

Volume 2 Page 15, PIE 4.0, The High Speed PIE:

PIE 4.0

The latest incarnation of the PIE is kind of a step back to an earlier design as well as a step forward to push the limits of PIETECH possibilities.

 


I am using a single wheel (for now) with a much lighter weight, even lighter than the PIE 1.0 design. I am trying out a quiet gear set which uses a 14mm pitch timing belt as the teeth which is fastened to the same size (3.5″) steel pulley as used on the PIE 1.0 & 2.0, and although it is quieter I am not sure if the teeth are robust enough to use as a spur gear.

Initial testing of the PIE 4.0 is very encouraging, although there are some small issues arising from the increased speed which has currently been measured at just over 750 RPMs. The most serious issue has been the used motor I pulled off of the storage shelf. Although the 110 volt motor was marked as “Good” because it runs well without a load, it quickly overheats and shuts down when it is turning the PIE4.0. The other issue is the soft gear design which seems to work well most of the time, but has “slipped” out of time on several test runs. I may revert to the welded steel gears before I am done since I still do not feel that purchasing expensive spur gears in this size range, just to risk having them destroyed if the design fails elsewhere, is an acceptable risk. Eventually I am sure that it will become necessary in order to achieve high speeds for extended periods of time.

The lighter weights (2 oz. including the pivot bushing) are actually performing better than expected as thrust becomes readily apparent in the 100 to 200 RPM range, although a better study of this is required.

The PIE 4.0 has only been bench tested so far, but it easily moves my bench around when it is clamped to the surface of it. Since the PIE 2.0 was just barely able to move the bench, I am encouraged to keep pushing forward with this high speed unit.