View Full Version : can?

jon_curtis - n/a
16-Feb-07, 02:58 PM
can a rotax be suspended/hanging from mounts like this rather than sat on them?

i dont mean the engine hanging upside down, with these mounts in compression sat on a bit of angle or box.

i want to bolt up into a bit of box section with the engine hanging off the plate?

will mounts like this cope? its not very fail safe tho i supose.

hovmart - n/a
16-Feb-07, 03:45 PM

kevinf - n/a
16-Feb-07, 05:54 PM
Are you proposing to hang the engine from the cylinder studs rather than from the mounting points on the crankcase? Personally I wouldn't - 8mm dia. studs which are already doing another job vs 10mm dia bolts dedicated to holding the engine down - no contest in my book. You'd also get a lot more movement at the PTO. The distance from cylinder head to centre of crank is far greater than from std. mounting points to centre of crank, so unless the mountings were very stiff you will be more likely to throw a belt or, if using a gear box more likely to get blade/duct strikes. You would need more clearance for safety and loose out on efficiency. With very stiff mountings you are more likely to get breakages from stress and vibration too.


erbus - n/a
16-Feb-07, 07:01 PM
It was done that way on a cuyuna (the motor is upside down due to gearbox position in this case),there are 5 stiff av mounts on the bottom (they had to be stiff to cope with the engine and blade tip movement)


Hovertrekker - n/a
19-Feb-07, 01:58 PM
There's nothing wrong with mounting the 2-stroke engine upside down as long as you're using the proper crankcase mounting holes. Neoteric does it with all their hovercraft. http://www.neoterichovercraft.com/

jon_curtis - n/a
19-Feb-07, 07:35 PM
i am indeed going to use the proper mounting holes, i thought the plate pic would illustrate that!

the question is not can i hang a rotax upside down, the question, is will those mounts (in the pic) take the load of hanging said rotax off them!

team black - n/a
19-Feb-07, 07:41 PM
The mounts shown are not fail-safe, the metal core tends to separate out. Yes they will take the weight, the issue is how long they'll take it for!! You'd probably do better to make sure they're in compression rather than tension

jon_curtis - n/a
19-Feb-07, 07:45 PM
hi ewan thats what i was thinking!

hmmm! thanks for the advice! back to the drawing board!

GavinParson - n/a
19-Feb-07, 08:12 PM
The Rotax 447 I used to have came out of a microlight and mounted exactly like that with the same mounts, I still have the mounting plate.

If the CAA approve them to hang an engine 2000ft up in the sky I'm sure they're secure enough in a hovercraft.

hovmart - n/a
19-Feb-07, 08:32 PM
the trick is to use repair washers that are larger than the hole for the mount in the plate and then if the mount fails it will only fail to the washer, it would also be good to make a mount to the head to stop the twisting moment, works on lots of microlights

jon_curtis - n/a
19-Feb-07, 08:51 PM
hi hovmart

yeh, i took the engine out of a microlight, but i think it was sat on the mounts! anyhow, yeh the last two head bolts closest to the mag end, had a bar with two more mounts on, im gona do the same!

thanks for the advice!