Engine Update 4-15

Engine Update - 4-15

Finally we have an update - sorry for the delay.

We've been making a number of engine modifications and thought the best way to show them was with a talking picture book.  The youtube video shows some of the latest engine modifications to date, following below is a short description of the significant modifications.

We're still in trial mode debugging and refining.  To date the biggest design changes have been with respect to the displacer.  The fin design of the displacer added too much weight to the reciprocating parts of the eninge.  The displacer, after lighting weighed in at about 20 lbs.  Think of a 20lb mass, reciprocating a 14" stroke,with a frequency of 240 cycles per min, just not going to happen for this design.

The new displacer is made out of closed cell foam and fiberglass board (hot end).  The weight is down to about 9lbs and we think there is still a pound or two that we can get rid of from that on the next itteration.

In addition, we strengthened the input and output shafts with two more bearings which add a good deal of rigidity to the crank mechanism (in green).

We also added a second flywheel - ending up with about 40lbs in total flywheel weight   With the expansion of the displacer, so grew the hot cylinder to accommodate its length of 40".  The reason for lengthening the displacer was to improve the heat transfer for the movement of the working gas.   None of the performance aspects of the engine change with this change in displacer length.  Still the same amount of compression and same sweep volumes (close to the same).

In running our tests, we added some insulation to the fire box allowing up to reach 350C and higher if needed.

Currently we're working on the piston sealing - there seems to be too much friction with the configuration we are using today (3 delin rings). We are looking at alternative materials that will provide a similar seal with less friction costs.  

Thanks for the continued support - Keep it coming ?

Working to get another update out shortly.

Engine Trials #2

Hi Folks,

Quick update -

We've finished the modifications to the kinematics for more axle structure.  Still working out the lightening of the displacer - look for that within a week.

Also, find an updated production schedule based upon where we are at today.  The schedule is somewhat disappointing in that we had hopped to have a significant number of the engines shipped by this time.

To that end, we put out a call for additional funds so that we can add people and improve the time for delivery.  The fundraising is happing via Indiegogo - http://igg.me/at/volo-engine/x/2577846

We are looking to raise $15,000 in funding to add additional folks to the team and get our production ramped up.  This will help us push the schedule, by how much, we won't know for about two months.

Till then we are  working full out getting these modifications completed, getting the engine up to running speed and moving towards shipments.

Thanks again for all your support -

If you know of any individuals or business that may like to support this project please pass the word.

Yours,
Tim Sefton

Engine Trials #1

Running tests on the engine - still cycling by hand, not yet running on heat.

From cycling the engine we've found three design improvements that we need to make.

1)  Displacer is just too heavy - this one clocks in at 22lbs - design weight is 14 lbs and thats still is too heavy.    To lighten this component up, we'll re-cast and dropp the extra weight and then actually drill out lightening holes on the back side of the fins - target weight is about 8 lbs.  This will add some machining time to the displacer caps, but this is crucial component for engine efficiency and worth getting it skinnyed up as much as possible.

2)  Key way for displacer to piston alignment - in cycling the engine wer're seeing some minor rotation of the piston in the cylinder, relative to the displacer.  This alignment between the piston and the displacer must be tight or the fins will crash into the piston.  The design change will incorporate a small aluminum channel on the displacer rod that will match like a key to the piston center gasket and maintain this alignment.

3) Support Axle bearings - in cycling the engine we are seeing some deflection of the axle bearings.  To better suppor the axles we are going to add an ear (once we get it in place we'll show you a picture and it will make sense) and an additional bearing on each axle.

Everything else tests out pretty well, noticing a small narrowing of the cold cylinder bore, we re-sized the  rings to a custom fit and it seems to be working well.  Going to want to beef up the bore cutting head tool on the next set of cylinders that we bore out so we get rid of this distortion.

Currently we running heated trials of about 450 F on the hot end of firebox and seeing about 300 F on the engine head - we'll need to get up closer to the 450 F temp on the head - don't see that being a problem - just need a bit of insulation on the firebox.  We've been running these tests at ambient temperatures of about 30 F, so from one end to the other end of the firebox we are seeing a big drop.


We've got the new displacer caps cut and are getting ready for a casting pour to get those underway.  At the same time, you'll be happy to hear we have started to cut 5 sets of foam for the first 5 engines, so as to get the production process turned up.  New schedule should be out shortly.

Tim


PS
One other note - one of our early supporters (in Slovenia)  was motivated to build his own engine based on the Volo design (minus the displacer / piston / head fins) - just got it running after about a years time - looks very cool and is running (although with out the fins - the performance and output is very low)  - Check it out here -  Love to see the engine start spreading -

https://plus.google.com/u/0/photos/110230689089207649183/albums/5723348259299888737?cfem=1

Assembly Complete !

Engine is assembled !

Tightened down on the last gaskets and tested all the kinematic linkages.  We are starting the trial phase and will have more of an update shortly.

We did make some design modifications in the engagement of the fins to the piston.  There is very little engagement, so we expect power to be lower due to a less efficient heat transfer process.

As we continue refining the lost foam casting process for these components the engagement will improve.

Next phase is engine trial - we'll first check each of the sealing surfaces for leaks and see what type of pressures we can hold in the cylinder.   It was a bit of a late evening, so don't mind the mess.

Tim

Back At It

After about 2 weeks of a aluminum welding fiasco, we cast another head and are back on the assembly and trial phase.

The casting came off significantly better then our last casting - still had a few gas voids but nothing like the first, the process has improved greatly.

Couple of photos from the casting - primarily difference was two fold - first we used a lot more vents for the foam gassing.  The only gas voids we did get were from flat areas where the geometry trapped the gas from venting.   Every top suface must be vented.  The second improvement was to use some green sand for the interior fins to better combat gravity of the sand wanting to drop out prior to pour.

Here in the first photo we have the model coated and vented - using the drywall slury, you can't see them all but there are 5 vents in addition to the sprue on the top side of the model (this is the orientation of the model during the pour)

The next photo is our casting set up - yes it cold out in Michigan in January - Looks a little redneck, but no problem doing a 40 lb pour with this setup.  Foundry is in the foreground and casting pit in the back ground - a wash tub does the trick here - with the model coated we use primarily play sand for fill.  We did use some green sand for the interior fin slots but not much.

 

Here is the part right out of the sand, looks a little rough but not bad.  The snow did add a bit of mystery to pour - misting looks like the gates of hell.

 


Here you can see a comparison of our first head pour and then the current part.  Big difference - on the first part we spent at least 8 hours of machining time - figuring out the best way to clean up the interior fins.  On this last part, total machining time was about 2 hrs -

 

Back to engine assembly - more updates to follow.

Tim

Assembly Update - 12-24

Not quite the picture we wanted to post on Christmas Eve but its been so long since we put out an update we wanted to get something out there.  This is the engine head.  We had some leaks in the head aluminum from the casting so we sent it out to a professional welder to have them patch it - this is what we got back after two weeks.  Ugh, and its still is not sealed - turns out tig welding on cast aluminum is a bit tricker then they originally anticipated.  

We are going to try one last operation on this part to seal it up and continue with the trials but it may require us to re-cast the part.

Hoping everyone has a warm and happy Christmas - May all your Christmas wishes come true (all we want for Christmas is a sealed head for our Volo Engine !)

Enjoy,

Tim

 

Engine Update - 11-2012

Quick Volo Engine Project update.

Kinematics are complete, sensors are on deck - I've got a short video update for you below.

Ziad has started cutting foam for our first set of engines !  We'll keep you apprised of progress on that front.

We had a short profile piece done on the engine from Metromode "5 Cool Inventions in Detroit" - you can see it here if interested - Metromode Article on Volo Stirling Engine.

More to come shortly.

Enjoy,
Tim