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Psru bellhousing

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slociviccoupe

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Looking for thoughts on the psru bellhousing or adapter to the engine. Run something similar to an enclosed bellhousing that encases and closes off the flywheel, adapter, drive coupler.
Or a machined "engine plate" with spacers to mount the gearbox allowing cooling to the rubber damper, inspection of damper , inspection of flywheel.

Basically what is more desirable? Sealing off these components in a bellhousing or mounting the psru and these components being visable.

Few examples are autoflight and spg are enclosed cast bellhousing type. And the eggenfeller and geared drives are the plate type with exposed components.

Using an spg gearbox and not to pleased with the bellhousing provided. Working with them on it but was thinking being able to inspect would be nice and the plate type mount also gives provisions for engine mounts and not using engine as a stressed member mounting it with the gearbox pulling on the engines bellhousing end.
 

wsimpso1

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A circumferential enclosure is strong and stiff at low weight. You can still put inspection ports in a bellhousing like adapter between RFOB and the gearbox. Going into failure mode management, failure of coupling components with an open arrangement is more likely to shed parts than with a full enclosure. Another failure mode to be avoided is to keep the prop shaft and gearbox attached to the RFOB, and that issue is not clear cut between the built up spacer type and the bellhousing type.
 

rv7charlie

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I'd think that a significant factor for a one-off would be build-ability. Casting a truncated cone you can trust to be void-free, strong enough *and* light enough can be a tall order for home construction. Don't know about the rest of you, but I'm pretty sure I'd stand a better chance of making a successful one out of plate.
 

slociviccoupe

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On my spg bellhousing they used 4 bolts of the phase 1 subaru for mounting instead of the 8 available on my phase 2 block. The starter pad is too thin and starter at wrong depth. Starter pocket wrong bore for older auto or large diameter starter. The spacing for the coupler is off also. The adapter that bolts to flywheel that drives the rubber guebo has receses in it for the drive lugs of the psru. If the coupler were to fail it should still drive the gearbox even though would tear everything up and make heck of a racket would still drive the prop. Well bolting it up with no coupler i can spin the prop flange and it doesnt touch the adapter.

The bellhousing provided very soft. Seems like not heat treated at all. Manufacturer said its soft to avoid cracking and soft allows thinner casting to be used.

Ive been in contact with manufacturer about the changes needing to be made. Hopefully i get a new bellhousing out of it.

Which brings up shape? It came dome shaped, but in the redesign wondering should i copy the dome shape or just give it a tapered shape with gussets to the block mounting locations.

Plan is draw it up in cad, cnc router one out of wood or foam and test fit. Or 3d print one. Send off for casting.
Was thinking about CC601 heat treated to T6 for bellhousing reccomended from another vendor. I would have figured a356 to t6 would be adequate as the subaru block should made of.
 

Geraldc

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I prefer the Aeromomentum or Viking type. An enclosed bell housing will not contain much in the event of a failure because it has to be built light.
Thats why drag cars have scatter shields.
Just thinking you could use a kevlar scatter shield
 

TFF

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The Wittman Olds used an auto housing. Not sealed but it was direct drive. FOD would be a concern if you think something could jam it.
 

Lendo

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PSRU Housings, I've built some , a lot to think about, including what gearing or other reduction type your using, Have a look at the Mistral housing design, I prefer that one to my own design. Even with Aluminium it starts to get weighty that's why Mistral (Rotary) used a lighter material. If I were to look again I might consider a Light steel 3D printed housing. I've found sand cast Al. can have some porosity, Pressure injected cast Al is much better and Foundry extruded Al to be the most dense and strongest. All require a financial investment in one way or another, including 3D printing.
There is of course the design, have a look at Powersport design, it's very good (again for a Rotary).
Good Luck.
George
 

pfarber

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I think the easiest would be turning a billet. The SPG PSRU adapter I plan to use is a few inches long and automotive bellhousings are known for a pretty steep taper... so finding a chunk of Al large enough to turn would be interesting.

Lots of PSRUs are bolted up with not much more than C-channel.
 

rv7charlie

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Slociviccoupe,

Is this the Air Trikes drive & adapter? Can you post pics, especially detail images of the coupler drive/driven components without the Guibo?

Thanks,
Charlie
 

GTX_Engines

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Are you planning on installing a Subaru? If you don't already have one I would advise against starting out from scratch with one. They weigh twice as much as other much more modern conversions such as Yamaha with a relatively poor service record compared to them. I have a fleet of dozens of Yamaha 150HP engines flying, 165 lbs all-up installed weight, over 10,000 fleet hrs with zero forced landings. Been running them for close to ten years now. Others have had the same success with them.

As far as the above mention of "built up plates" vs one-piece adapter goes, so long as the modular components are properly pinned and bolted to the engine and gearbox you are fine. I build and offer a two-piece modular Yamaha adapter that is precision aligned and pinned. The "collar" that pins to the engine is water jet cut billet aluminum, 1-1/2" thick, pinned in two places to the engine. The adapter plate is pinned to the collar. The two-piece adapter is held in place with 10-11 stainless steel M6 socket cap screws. The advantage of this design is that it easily accommodates several different gearbox types, whereas a one-piece CNC adapter limits you to a single type gearbox.

I had a prop strike once with this two-piece 165 HP adapter with no indication of any shift or separation whatsoever. Very strong and reliable design! Again, 10,000+ hours of normal operation w/o a single contraindication, either. It's just gotta be done right from the get-go. That's all. Others have tried and failed to copy my design. It isn't as easy to do as it looks.

Wherever you have any kind of shaft coupling you should have inspection holes large enough to pre-flight the condition of either your clutch or your rubber flex shaft coupling. Also, holes provide cooling. Rubber shaft couplers produce heat, as do any type of clutch. Some PSRU's have a sprag clutch inside the gearbox itself, such as the old Arrow gearboxes that came with their 500cc and 1000cc 2-cycle engines. I've used one of these PSRUs on a 150 HP Yamaha and it is wonderful. The advantage is the pinion gear bolts directly to the engine PTO, thus making the complete power plant 3" shorter than using an AK7 gearbox, Rotax C, or SPG. Auto Flight is good stuff, but much larger and heavier.

I've never heard any complaints from Subaru guys using either Air Trikes' product or Auto Flight. I'd have to guess it's a matter of personal taste/preference.

Happy flying. For more info or questions drop me a line info@mohawkaerocraft.com
 

slociviccoupe

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Yes i have a subaru already. Yes it is spg-5 full kit. This is the second one thry have made. Its all their coupler, guebo, and gearbox.
I am using subaru because of 2 other very good flying examples. No im not just sticking a used car engine in a plane snd going flying. Its being converted for aircraft use with forged pistons. Opened up bearing clearances and the necessary oiling modifications. As for not using the yamaha it just doesnt fit my application. Im going for 200hp max. That and ive worked on yamaha engines and though i love them the rpm's they turn to makr the hp makes me uneasy on the ground or in the water i would not feel comfortable in a plane. That and my supercharged yamaha jet ski is very thirsty. Also the subaru boxxer configuration fits. If i were to use any other engin would be the honda f22c out of the s2000. It just doesnt fit unless leaned over.

Ill try to grt some photos up. Do i just upload them or do i have to use file sharing host?

I will say there is lot of bad rep on subarus because of mainly 1 person. Meanwell airtrikes has a lot of spg-4 flying on ej22 in gyroplanes with no failures. So i trust it. Just not plessed with this bellhousing
 

rv7charlie

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To upload pics, just click the little 'landscape' icon (10th in the row, between the 'chain link' and the smiley) above the reply composition window. Then you can click in the popup box, and find/click on your image file on your computer.

What did Air Trikes say about the fact that the drive & driven pins don't overlap? I thought they used a Guibo type soft element, which would require the pins to overlap. Is it some other type coupler?
 

slociviccoupe

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I have been in contact with vasilli from air trikes. And working on getting him the corre t info to remedy this. This isnt a bash on spg. im no engineer but just a guy very good at cad, machining and fabrication. I just want to go about this correctly.

My choices are weld the extra bungs to his bellhousing , make centering ring for starter and spacer for the mount pad. And send it all back with cad file for bellhousing bolt pattern.
 

slociviccoupe

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In 4th picture down i would assume the recess cut out in the guibo drive adapter the drive lugs from the gearbox would pass through the rubber damper and into the recrss of the drive adapter. That way in any way it failed it would still drive the gearbox.

I can remedy this but machining the thick spacer ring on the bellhousing down to accomodate this.

My only thoughts are on this is air trikes said use an auto flexplate. Problem is aito flex plate doesnt have a ring gear. Ring gear is welded to the converter. After ross had to add weight yo his marcote flywheel i went with the heaviest chromoly flywheel i could find. I can reduce weight later. My guess is the thickness at the hub where the bolts mount flywheel to hib might be different from oem flywheel to an aftermarket one. This would be made even worse by an auto flexplate and even then the adapter wouldnt work because it centers on the pilot bearing bore which is in the manual flywheel.

Which brings back up the stsrter issue. Older phase 1 had a gear to gesr reduction stsrter with the squarish solenoid. It had the larger spigot diameter. My starter the inline planetary type has the smaller spigot bore
 

rv6ejguy

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Are you planning on installing a Subaru? If you don't already have one I would advise against starting out from scratch with one. They weigh twice as much as other much more modern conversions such as Yamaha with a relatively poor service record compared to them.
Really? There are 2-3000 Subarus flying worldwide for over 25 years with many hundreds of thousands of flight hours collectively. A high time one in Australia used for gyro training had 3800 hours on it. The RAF gryo fleet were all EJ powered, over 500 of them with well over 125,000 flight hours on them as of 15 years ago. I have hundreds of customers flying them and they work just fine. Not sure where you are getting your information from?

 
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