Volvo D6 DPR drive/HuntonXRS37 - Page 2

peterunwin · 20-11-2011, 05:44 PM

Hi All,
Started further modifications on Cheetah's propellers, first mod is to reduce blade area of the front prop thin the blade edges and then make a jig to press more pitch into the blade, blade area on the rear prop is ok they just need pitching up. Part of the reason for reducing the blade area is to equalise the torque between the two prop shafts and as i don't run superchargers the new hybrid turbos won't spool up quite so early so it should assist getting on the plane and give more speed due to less drag.

Peter

peterunwin · 30-11-2011, 11:30 AM

Hi All,
Removed both drives and brought them back to the midlands, they are now totally stripped and all parts have been inspected.All the gears are perfect some of the bearings are showing signs of wear & tear so i will re-build them with new bearings and while they are apart i will modify the casings for the semi dry sump system.

Peter

larby · 30-11-2011, 06:47 PM

Good to know they're holding up well!
I'm changing the Revenger to a DP-X drive, the swept back newer version. Are you taking the lowers apart? I'm interested in converting mine to single prop to increase it's power handling ability. Would you have any idea if any of the other drive lowers would bolt on, or from an engineer's point of view, how hard it would be to convert the DP lower to single prop.

Cheers, James

peterunwin · 01-12-2011, 10:44 AM

Quote:

Originally Posted by larby

Good to know they're holding up well!
I'm changing the Revenger to a DP-X drive, the swept back newer version. Are you taking the lowers apart? I'm interested in converting mine to single prop to increase it's power handling ability. Would you have any idea if any of the other drive lowers would bolt on, or from an engineer's point of view, how hard it would be to convert the DP lower to single prop.

Cheers, James

Hi James,
Yes the lowers are stripped as well, i tend to do this every 2-250 hours or sooner if i feel anything that i am suspicious of, doing this has prevented quite a few catastrophes as the poor lubrication and the high temperatures seems to have a detrimental effect on the bearings, this should be corrected with my semi dry sump system and i will be able to use a much lower oil level pulling the oil from the bottom gear case in through the transom, through a filter and returning it to the top bearing in the upper which at the moment only gets splash and to add insult to injury it is a shielded bearing which again i am going to modify.Converting a duo prop to single would be pretty easy but the torque would then pass through only one gear instead of two which would put considerably more pressure on the vertical shaft needle roller bearing and gear teeth. I think reducing the blade area of the propellers is probably a better way to go especially on a single engined boat, I have had excellent results doing this on Cheetah.

Peter

Scand · 01-12-2011, 11:53 AM

Quote:

Originally Posted by peterunwin

Hi All,
Started further modifications on Cheetah's propellers, first mod is to reduce blade area of the front prop thin the blade edges and then make a jig to press more pitch into the blade, blade area on the rear prop is ok they just need pitching up. Part of the reason for reducing the blade area is to equalise the torque between the two prop shafts and as i don't run superchargers the new hybrid turbos won't spool up quite so early so it should assist getting on the plane and give more speed due to less drag.

Peter

Have you considered having some new props made out of proper stainless steel.
There are a few companies in your area that CNC machine props out of nice stainless.

larby · 01-12-2011, 12:26 PM

Ahh yes, I see what you mean there. Looks like I'll stick with the two and get them worked then. Did you reduce blade area yourself or if not, who did you send them to?

What work have you done to the lower case too? It looks as though you've added a nosecone and re-shaped the skeg?

James

peterunwin · 02-12-2011, 06:52 PM

Quote:

Originally Posted by Scand

Have you considered having some new props made out of proper stainless steel.
There are a few companies in your area that CNC machine props out of nice stainless.

Hi Petter,
Sounds interesting wouldn't mind their contact details? I was under the impression that the spiral spline in the hub was patented? so my thoughts were when i have run out of development on the volvo props i would cut the hubs out and weld them into some high performance merc props to get round the spiral spline issue.

Peter

peterunwin · 02-12-2011, 07:31 PM

Quote:

Originally Posted by larby

Ahh yes, I see what you mean there. Looks like I'll stick with the two and get them worked then. Did you reduce blade area yourself or if not, who did you send them to?

What work have you done to the lower case too? It looks as though you've added a nosecone and re-shaped the skeg?

James

Hi James,
Steel Developments did the early development work, but always being one to learn new trades i started modifying blade area and pitch myself i keep a mould of the shape and blade area for reference, the lower units have been extensively modified, nose cones have been fitted along with a considerable reduction in skeg area.The latest modification is to remove the cavitation plate we will see how this goes......

Peter

larby · 02-12-2011, 09:12 PM

Sounds great! Any detail on the skeg/nosecone you could give me would be great! I'd love to sort a nose cone but can't find one to fit so far...

What's the reason behind removing the cavitation plate?

Cheers, James

peterunwin · 06-12-2011, 03:05 PM

Quote:

Originally Posted by larby

Sounds great! Any detail on the skeg/nosecone you could give me would be great! I'd love to sort a nose cone but can't find one to fit so far...

What's the reason behind removing the cavitation plate?

Cheers, James

Hi James,
The nose cones were made from billet aliuminium profiled on the inside to suit the shape of the original gearbox pointed on the outside, i then bonded them to the gearbox with epoxy paste and then a wrap of carbon cloth, the profiling was done with body filler. I cut around 50% of the skeg away and made it much more streamlined, the bottom now reaches to the same position as the propeller blades. The removal of the cavitation plate is to see if it reduces drag, the tip of the blade is quite close to the underside and i think causes some unwanted turbulance so much so that both cavitation plates have fractures in them just above the propellers.

Peter

peterunwin · 14-12-2011, 05:01 PM

Hi All,
I have removed Cheetah's engines and i am now in the process of re- engineering the engine mounts to position the engines 5" further forward this will allow me to run much bigger exhausts, make general service a lot easier and will also help with the centre of gravity, at the same time i removed the battery boxes as the new lightweight batteries are being relocated to the bulkhead.The drives have also had plenty of attention i am in the process of setting the backlash on the gears and the preload on the bearings, i have also sanded the black paint down to the primer so they are now ready to be repainted.

Peter

peterunwin · 28-12-2011, 02:25 PM

Hi All,
I have decided that while making the modifications to the engine mountings as well as moving the engines further forward i am now going to move them closer together, this will have the same effect as raising the drives but without making the centre of gravity higher, at the same time i have been able to make some weight savings.This coupled with the increase in power should see the power to weight ratio rise from 145HP per tonne to 185HP per tonne.

Peter

Mikko Oikari · 28-12-2011, 03:45 PM

Hi Peter,
As I mentioned on the phone the driveheight on Vilda was very sensitive.
I tried every height you can think of and ended up with the center of the cavplate 35 mm above the bottom.
Up to 60 mph everything was better with the drives 25 mm lower but above 60 mph I both lost speed and stability. To much material in the water.
With the drives 25 mm higher the loss of speed was 15 mph. Lots of ventilation as the DuoProps need much water around them.
Vilda has a twin-step bottom and behaves different than yours. I could never go higher than +1 on the trim.

jw. · 28-12-2011, 07:11 PM

Oh that's interesting Mikko, how did you pad it out to two spacers thick? Did you make the parts?

Mikko Oikari · 28-12-2011, 08:20 PM

Quote:

Originally Posted by jw.

Oh that's interesting Mikko, how did you pad it out to two spacers thick? Did you make the parts?

Made the parts. The parts to the vertical shaft were made by a guy working at Volvo. In his spare time...

peterunwin · 30-12-2011, 10:49 AM

Quote:

Originally Posted by Mikko Oikari

Hi Peter,
As I mentioned on the phone the driveheight on Vilda was very sensitive.
I tried every height you can think of and ended up with the center of the cavplate 35 mm above the bottom.
Up to 60 mph everything was better with the drives 25 mm lower but above 60 mph I both lost speed and stability. To much material in the water.
With the drives 25 mm higher the loss of speed was 15 mph. Lots of ventilation as the DuoProps need much water around them.
Vilda has a twin-step bottom and behaves different than yours. I could never go higher than +1 on the trim.

Hi Mikko,
The current drive height is 25mm above the bottom and i am going to try them at around the 50mm mark which i think will be ok on an antique unvented hull, also when i fitted the nose cones it made a huge difference in propeller grip. Up to about 50 knots i have to run a negative trim -2 or 3 degrees 50 knots to max velocity a gradual increase to positive trim to +7 degrees.

Peter

Tom Stone · 30-12-2011, 12:43 PM

Quote:

Originally Posted by peterunwin

an antique unvented hull

don't let jeff hear you say that

peterunwin · 15-01-2012, 12:57 PM

Hi All,
Having removed Cheetah's engines, drives and transom shields i decided it would be a shame to waste the opportunity... so she has been on a bit of a diet everything that we don't use has gone along with all the wiring which is to be replaced by a new lightweight system. I have also decided to reduce the drive centres by 150mm and down by 35mm this will set the drives 25mm higher relative to the bottom than they are now hopefully giving more bow lift and less drag.The total weight saving will be around 300KG.

Peter

Dynamic · 17-01-2012, 02:09 PM

hi pete

firstly some amazing work on both your hunton projects. great to see something special and someone putting so much into it.

but could i ask why such a drive to lighten the boats? my understanding is hunton's are exactly built that heavy to begin with.

peterunwin · 18-01-2012, 04:58 PM

Quote:

Originally Posted by Dynamic

hi pete

firstly some amazing work on both your hunton projects. great to see something special and someone putting so much into it.

but could i ask why such a drive to lighten the boats? my understanding is hunton's are exactly built that heavy to begin with.

Thanks Dynamic, reducing the weight by 300KG is roughly equivalant to an additional 40HP and as i am trying to make the boat as quick as possible every little helps. Virtually all of the reduction in weight is behind the centre of gravity, as the D6'S are pretty heavy any reduction in the rear will be of benefit.

Peter