Prop Ground clearance issues

[Wingover1]

Hi Everyone

I had a Suzuki AT10 Turbo engine mounted in my Bushbaby 500 but the gearbox sits to low resulting in only 3 inches of prop ground clearance when the tail is horizontal with a Warp Drive 3 blade ground adjustable prop. To change the prop is an option but then it is a 68" and I don't know if that will really give me enough clearance and the recommended prop size is a 72" Putting larger tires on is another option having 600-6 at the moment but once again how much clearance will I get by putting on 850-6. I had a Rotax 582 in but that seized up and is also under powered for my purposes. The other option will maybe to fit an extended landing gear. If I raise the engine then the visibility will be effected and the cowl will have to be raised. I have spend a lot of money on this project and has burned my fingers through out by getting advise and work done by "experts" Has anyone had similar issues and a best solution or suggestion please?

[PapuaPilot]

Going to 8.50x6 tires will raise it 2.5" to 3" and that is the easiest fix. The next best thing would be to get a new landing gear.

Here is what the FARs say:
§ 25.925 Propeller clearance.
Unless smaller clearances are substantiated, propeller clearances with the airplane at maximum weight, with the most adverse center of gravity, and with the propeller in the most adverse pitch position, may not be less than the following:
(a) Ground clearance. There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level takeoff, or taxiing attitude, whichever is most critical. In addition, there must be positive clearance between the propeller and the ground when in the level takeoff attitude with the critical tire(s) completely deflated and the corresponding landing gear strut bottomed.

[Wingover1]

Hi Phil

Thank you very much for your help and suggestions. Once our lock down is lifted I will definitely start with the tires first. Those 8.50-6 are difficult to get here in SA and are horribly expensive (if you can find them) with our Rand being nearly 18 for 1 USD and plummeting. a Friend of mine made a suggestion to put 8 inch rims on because you have a much wider selection of tires ATV/Ride on Lawnmowers ect. and probably a third of the price . Will this be an option? iow would I be able to replace the 6" rims with 8" rims?

[PapuaPilot]

I didn't notice that you were in SA.

Going to 8" rims could be a better choice if you can get less expensive tires. If you change the rims it will probably require a different axle to get the proper axle diameter and length to fit the rims.

Whatever way you choose it looks like you need get your main gear a minimum of 6" higher. If I remember correctly 6.00x6 tires are 16" diameter. This means you would need a minimum of a 28" diameter tire if you want to fix this problem with bigger tires. I am guessing you would have a prop strike if you ever landed with a flat tire and the strut bottomed.

It might be a better choice to extend your landing gear legs by 6". Then you can still use the 6.00x6 tires and wouldn't risk a prop strike with a flat tire.

[Wingover1]

Thank you Phil

This will probably be seen as a structural modification ?

[Av8r3400]

Running out of clearance is a problem...

oops.jpg

[Wingover1]

Not nice and a expensive lesson, shame