I was looking at the weights and prices of Scott Casler's Hummel Engines at and decided to draw up a table of weights and costs per horsepower of his basic engines. I then went over to Steve Bennett's Great Plains and pulled just cost numbers for his more complete packages. This is not meant to be a comparison of the two suppliers as these are apples and oranges, it's just a look at some of the options and the cost/benefit of the various drive systems. In all cases I have used the higher number when both takeoff and cruise horsepower were given.
HUMMEL ENGINES (single-magneto, hand-start)
*Nikasil cylinders are standard on this model
What's interesting above is that all the four-cylinder engines are substantially cheaper for the horsepower and sometimes lighter per horsepower than the two-cylinder engines, and in fact you can go up to a 1915cc 65 horsepower full VW and still come in cheaper than a 1200cc 45 horsepower half VW. Adding an exhaust system, dual ignition and a starter/alternator would increase the cost and weight of all the engines, of course, but would still favor the four-cylinders since those options for the two-cylinder models are cheaper and lighter but not by very much.
The Great Plains site lists complete kits with dual ignition, carb, alternator, starter, etc. and also offers direct drive(pulley end) , flywheel drive and redrive options. Just focusing on price, I get these numbers.
GREAT PLAINS DIRECT DRIVE (magneto & electronic dual ignition)
GREAT PLAINS FLYWHEEL DRIVE (distributor & electronic dual ignition)
GREAT PLAINS REDRIVE (various acccessory options so I used flywheel drive prices + $1595 for Valley Engineering PSRU)
CONCLUSIONS
1) Unless you are building a true Part 103/SSDR ultralight or are otherwise in a situation when every pound is critical, or so strapped for cash that $1,275 makes the differenc between flying and not, then a half VW doesn't seem to make much economic sense. Moving from 1037cc to 1915cc you get 103% more power for 42% more cost, a great deal if you can take the extra weight.
2) The most bang for the buck in direct drive is the 1915cc. For a VP-1 or FRED or Jungster or another single-seater than can do fine on the smaller engine, then the $1,100 initial savings and reduced fuel burn are attractive. Otherwise you may as well go straight to the 2276cc which has the next best cost per horsepower and would be better for a two-seater.
3) For flywheel drive, you may as well go straight to the 2276cc regardless of the number of seats as the power gain is disproportionately greater than the slight increase in cost. Some people may not like, however, that both ignition systems require electric power in the Great Plains configuration.
4) Interestingly, redrive doesn't seem economical at all in smaller displacements. Simply moving to a larger displacement direct-drive engine is cheaper per horsepower. Also, since Great Plains quotes the same continuous power rating regardless of drive setup, then the redrive options are all actually the most expensive per horsepower in cruise. If you absolutely need the STOL performance of a redrive engine, then go straight to the 2276cc since, here too, the power gain is disproportionately greater than the small increase in cost.
I am sure not everyone will agree with my conclusions, feedback welcome.
Cheers,
Matthew
HUMMEL ENGINES (single-magneto, hand-start)
| DISPLACEMENT (cc) | CYLINDERS | POWER (hp) | WEIGHT (lb) | PRICE (US$) | LB/HP | US$/HP |
| 917 | 2 | 32 | 85 | 2950 | 2.66 | 92.19 |
| 1037 | 2 | 37 | 85 | 3450 | 2.30 | 93.24 |
| 1200* | 2 | 45 | 84 | 4450 | 1.87 | 98.89 |
| 1600 | 4 | 50 | 140 | 3950 | 2.80 | 79.00 |
| 1835 | 4 | 60 | 145 | 4150 | 2.42 | 69.17 |
| 1915 | 4 | 65 | 145 | 4175 | 2.23 | 64.23 |
| 2180 | 4 | 76 | 147 | 5300 | 1.93 | 69.73 |
| 2400 | 4 | 80 | 147 | 5600 | 1.84 | 70.00 |
What's interesting above is that all the four-cylinder engines are substantially cheaper for the horsepower and sometimes lighter per horsepower than the two-cylinder engines, and in fact you can go up to a 1915cc 65 horsepower full VW and still come in cheaper than a 1200cc 45 horsepower half VW. Adding an exhaust system, dual ignition and a starter/alternator would increase the cost and weight of all the engines, of course, but would still favor the four-cylinders since those options for the two-cylinder models are cheaper and lighter but not by very much.
The Great Plains site lists complete kits with dual ignition, carb, alternator, starter, etc. and also offers direct drive(pulley end) , flywheel drive and redrive options. Just focusing on price, I get these numbers.
GREAT PLAINS DIRECT DRIVE (magneto & electronic dual ignition)
| DISPLACEMENT (cc) | POWER (hp) | PRICE (US$) | US$/HP |
| 1600 | 55 | 5800 | 105.45 |
| 1835 | 65 | 5800 | 89.23 |
| 1915 | 69 | 5800 | 84.06 |
| 2180 | 76 | 6900 | 90.79 |
| 2276 | 80 | 6900 | 86.25 |
GREAT PLAINS FLYWHEEL DRIVE (distributor & electronic dual ignition)
| DISPLACEMENT (cc) | POWER (hp) | PRICE (US$) | US$/HP |
| 1835 | 65 | 6395 | 98.38 |
| 1915 | 69 | 6395 | 92.68 |
| 2180 | 76 | 6595 | 86.78 |
| 2276 | 80 | 6595 | 82.44 |
GREAT PLAINS REDRIVE (various acccessory options so I used flywheel drive prices + $1595 for Valley Engineering PSRU)
| DISPLACEMENT (cc) | POWER (hp) | PRICE (US$) | US$/HP |
| 1835 | 85 | 7990 | 94.00 |
| 1915 | 85 | 7990 | 94.00 |
| 2180 | 103 | 8190 | 79.51 |
| 2276 | 105 | 8190 | 78.00 |
CONCLUSIONS
1) Unless you are building a true Part 103/SSDR ultralight or are otherwise in a situation when every pound is critical, or so strapped for cash that $1,275 makes the differenc between flying and not, then a half VW doesn't seem to make much economic sense. Moving from 1037cc to 1915cc you get 103% more power for 42% more cost, a great deal if you can take the extra weight.
2) The most bang for the buck in direct drive is the 1915cc. For a VP-1 or FRED or Jungster or another single-seater than can do fine on the smaller engine, then the $1,100 initial savings and reduced fuel burn are attractive. Otherwise you may as well go straight to the 2276cc which has the next best cost per horsepower and would be better for a two-seater.
3) For flywheel drive, you may as well go straight to the 2276cc regardless of the number of seats as the power gain is disproportionately greater than the slight increase in cost. Some people may not like, however, that both ignition systems require electric power in the Great Plains configuration.
4) Interestingly, redrive doesn't seem economical at all in smaller displacements. Simply moving to a larger displacement direct-drive engine is cheaper per horsepower. Also, since Great Plains quotes the same continuous power rating regardless of drive setup, then the redrive options are all actually the most expensive per horsepower in cruise. If you absolutely need the STOL performance of a redrive engine, then go straight to the 2276cc since, here too, the power gain is disproportionately greater than the small increase in cost.
I am sure not everyone will agree with my conclusions, feedback welcome.
Cheers,
Matthew
Last edited:
