Cox Engines Forum
You are not logged in! Please login or register! Guests are limited to posting in the "General Questions (Guest Posting Allowed)" section only. Becoming a member is fast, easy and FREE!


Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» On the Ramp Right Now: The Pietenpol Reunion at Brodhead, Wisonsin
by rsv1cox Today at 10:16 am

» Aluminium fuel tanks for Cox Tee Dee .010 & .020
by 1/2A Nut Today at 2:30 am

» Surestart Engine Technical Drawing
by GallopingGhostler Yesterday at 8:32 pm

» 1975 Kawasaki KT250
by Cribbs74 Yesterday at 11:26 am

» Happy day Friend!
by getback Yesterday at 9:58 am

» **VOTE-ON-THE-NEXT-COX-ENGINE-OF-THE-MONTH** (July 2018)
by MauricioB Thu Jul 19, 2018 10:46 pm

» I Feel Good!!!!!!
by MauricioB Thu Jul 19, 2018 10:24 pm

» some star flowers ...
by MauricioB Thu Jul 19, 2018 10:23 pm

» Flying Saucer
by 944_Jim Thu Jul 19, 2018 8:54 pm

» 1961 cox mercedes benz racer
by crankbndr Thu Jul 19, 2018 7:20 pm

Cox Engine of The Month
July-2018
MauricioB's

"Tee Dee .020"



PAST WINNERS
Speed Contest 2018
CEF Traveling Engine

Win This Engine!
The Traveling Prop
Gallery


World of Aviation

Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Page 1 of 2 1, 2  Next

Go down

Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 12:02 am

As promised some pictures showing the internals of the prototype Cox Olympic 15 rear drum valve engine. I got this engine off of eBay in January.

Here is a picture showing the internal parts:



Someone looks to have polished the transfer ports to an almost mirror finish.



The venturi looks to have also been polished to improve airflow.



Here is the drum valve without the carb body attached.



I will post some pictures showing how a new carb body is being made. Hopefully I can find a material that is resistant to methanol but that may not be possible with the available urathane molding material available.

Link to the ebay ad:

http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&rt=nc&nma=true&item=330520764702&si=%252FNFbcLDkoIUj60PC4fUjv4d36xI%253D&viewitem=&sspagename=ADME%3AL%3AOU%3AUS%3A1123&orig_cvip=true&rt=nc

Jason


Last edited by Jason_WI on Wed Aug 08, 2012 11:42 pm; edited 2 times in total
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 12:38 am

Here are pictures showing the process of making a mold from a part. First a nylon plug is turned and milled to fit the inside of the carb body. The below picture shows the plug installed. The pressure nipple hole is also plugged. The clear plastic piece tacked on will be used to fill the mold later on.



Here the carb body is placed into moldeling clay. Modeling clay is used to make 1/2 of the mold. The piece is set in about 1/2 way. The important step here is the fine smooth transition from the part to the clay. The silicone mold material picks up very fine details so any imperfections here will show up in your final piece.



Next wood blocks are set up around the clay to dam up the part. The clay is smoothed out against the wood form. There are 3 keys blocks that are set in 3 corners. These will be used to align the mold halves. I think I used 8/32 hex nuts set about 1/2 way into the clay. I seem to have misplaced the pics showing the final stage just befor pouring the silicone.



Here is a part that was made form the mold from a high impact urathane. This material will soften up in methanol so not too practical to use.



Maybe I'll try 45 minute epoxy to mold a part but it may prove too brittle.
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  PV Pilot on Tue Nov 29, 2011 12:51 am

Thanks for the look inside. Funny that cox? Would polish up the transfer ports like that. Gotta atomize nitro as fine as possible to extract max power per lb.
avatar
PV Pilot
High Tech Balsa Basher
High Tech Balsa Basher

Posts : 1832
Join date : 2011-08-11
Age : 51
Location : The ragged end of the Universe.

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  RknRusty on Tue Nov 29, 2011 7:29 am

Does the same crank pin drive both the piston and the valve rotor?

_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!


My Hot Rock & Blues Playlist
avatar
RknRusty
Moderator

Posts : 10555
Join date : 2011-08-10
Age : 62
Location : South Carolina, USA

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  andrew on Tue Nov 29, 2011 7:43 am

Yes -- the lower end of the rod also serves as a spacer to keep the rotor against the backplate and the thickness of the rotor disk serves to keep the rod in place. The pin is sufficiently long to index in the hole in the rotor disk.

I wonder why COX chose to go the route of a rotary valve rather than the more common slotted disk and backplate. I would think that the rotary valve would require more power than a simple slotted disk. Would it be because they already had the carb body/needle valve/venturis from the Tee Dee that would fit?

What's the purpose of three holes in the valve disk? I can understand having two to allow for CW and CCW rotation, but not three.

avatar
andrew
Diamond Member
Diamond Member

Posts : 1226
Join date : 2011-08-11
Age : 70
Location : Western Kentucky

View user profile http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 7:54 am

The Tee Dee series wasn't introduced until the end of 1960. The Olympic rear drum was prototyped in 1959 and some were given away at the 1960 NATs. The carb body is different as the pressure nipple is on the opposite side as a Tee Dee carb body.

The crank pin is stepped and a smaller diameter sticks out to drive the valve.

I think the 3 holes were there so the venturi could point to one side or the other. Maybe someone here truly knows.

Jason
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  andrew on Tue Nov 29, 2011 8:33 am

Is the rotary valve body pressed into the backplate ring or is it free to be rotated? If it can be rotated, does it have any form of indexing to ensure that it goes in with the same orientation each time. The reason for asking is that if it may be freely rotated, then induction timing is fully adjustable -- at least to the point that the degrees at which it opens and closes may be changed. The duration is set by the size of the milled opening in the valve housing or in the valve itself.

The converse is if it is pressed in, then timing is determined by how far the backplate is screwed into the case -- and that could be hard to maintain in a production environment. From the pics, I couldn't tell if the valve body had a flat on it or not.
avatar
andrew
Diamond Member
Diamond Member

Posts : 1226
Join date : 2011-08-11
Age : 70
Location : Western Kentucky

View user profile http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 8:52 am

The valve body is free to rotate 360 degrees. There's no indexing and is locked in place by the threaded collar and the end cap. Timing is fully adjustable on this engine.
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Mudhen on Tue Nov 29, 2011 9:00 am

That molding is impressive. That’s quite a skill, Jason. It seems with cold molding that one is limited with the choices of material for the carb body. Is there a way you could make a mold that could be used for hot molding? You may open up to more possibilities in material. (Polystyrene, Delrin, or even aluminum.)
My engine is slightly different than yours. The ports were not polished. And, for the life of me, even with all the "tricks," I couldn't remove the carb body. (Goes way against my ocd Mad )
The problem with prototypes is the speculation. Unless there's a written record or one has the opportunity to talk to the engineers, than much is an educated guess. And over time, urban legends can develop which cloud the true history. If an urban legend takes root it can be difficult to dislodge.
Anyway, here's my guess: It seems that the aluminum rotor body was indexed to the crankcase. But to make up for slight differences in machining, plus the differences in atmosphere, temp. fuel, etc, the three holes could be used to adjust timing. In my case, the rotor pin was set in the middle of the three. The fourth hole seems to be set up either for balance, or for left hand rotation.
Mud
avatar
Mudhen
Gold Member
Gold Member

Posts : 387
Join date : 2011-09-19

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  andrew on Tue Nov 29, 2011 9:05 am

Jason_WI wrote:................Timing is fully adjustable on this engine.

That's pretty slick.

Would you talk a little more about how your mold for the carb housing is made? It's quite impressive, especially being able to maintain concentricity of the part. Is the silicone material pretty thin when added -- I assume it must be to match the fine detail. Is your mold a one time use or are you able to get the part free without destroying it.

Being able to reproduce small intricate parts is quite a skill -- one I wished I had.

andrew

EDIT: mudhen posted while I was typing, so you have impressed two of us with your abilities.
avatar
andrew
Diamond Member
Diamond Member

Posts : 1226
Join date : 2011-08-11
Age : 70
Location : Western Kentucky

View user profile http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Mudhen on Tue Nov 29, 2011 9:11 am

Jason_WI wrote:The valve body is free to rotate 360 degrees. There's no indexing and is locked in place by the threaded collar and the end cap. Timing is fully adjustable on this engine.
You can rotate the carb body within the threaded collar? That's way cool. Mine was frozen solid. That's why I thought the collar was indexed to the crankcase.
I think Socrates said it best: "Sweeeet!" c420 b.c.
mud
avatar
Mudhen
Gold Member
Gold Member

Posts : 387
Join date : 2011-09-19

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  shell shock on Tue Nov 29, 2011 9:22 am

Im not sure how it will react with nitro, but I have used JB weld for the longest time as a moulding agent. specially when i needed something to be fuel proof. Tough as nails too
avatar
shell shock
Gold Member
Gold Member

Posts : 401
Join date : 2011-10-05
Age : 26
Location : Mississauga Ontario, Canada

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 9:41 am

I never thought of using JB weld as a mold agent. I'll have to see if it can be thinned since it needs to be able to flow into all the fine details.

The silicone that is used to make the mold is thin and even picked up the cracks in the carb body and were reproduced in the first attempt. I ended up with a carb body with the same cracks as the original piece. On the second mold I used modeling clay to fill in the cracks in the original carb body and ended up with a mold that is nearly perfect.

As far as shape and concentricity the part fit on the the valve body with only minor scraping on the carb body with an xacto knife. The venturi threads in without having to run a tap into it.

The mold may last another attempt or 30 attempts. The carb body does come out of the mold hard where the threads are in the venturi. I suspect that this will eventually tear and the mold will be destroyed.


Mud,

I suspect yours is glued together with castor as mine was. Some heat with a monokote heat gun freed mine up. It took some persuasion with a wood dowel to push the carb body off of the valve.

Jason
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  andrew on Tue Nov 29, 2011 10:05 am

Jason_WI wrote:I never thought of using JB weld as a mold agent. I'll have to see if it can be thinned since it needs to be able to flow into all the fine details.

I considered mentioning JB Weld, but it's pretty thick. I don't know what solvent could be used without affecting the properties of the mixture. I'm guessing that being the confined in a mold, the solvent would not be able to gas off and that either the surface of the pull would be pocked or that it would end up being very porous and filled with a lot of gas bubbles.

If it would work, when cured, according to company information, JB Weld is petroleum, chemical and acid resistant. I'm not sure what resistant actually means -- it's pretty open-ended.

Another characteristic that is advantageous is that it has 0.0% shrinkage.
avatar
andrew
Diamond Member
Diamond Member

Posts : 1226
Join date : 2011-08-11
Age : 70
Location : Western Kentucky

View user profile http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  PV Pilot on Tue Nov 29, 2011 11:07 am

That's probably the reason for the 3 holes on the valve disk, timing adjustment.
avatar
PV Pilot
High Tech Balsa Basher
High Tech Balsa Basher

Posts : 1832
Join date : 2011-08-11
Age : 51
Location : The ragged end of the Universe.

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Mudhen on Tue Nov 29, 2011 11:37 am

This molding issue is way beyond me.
But here's a suggestion: Liquid Aluminum
http://www.devcon.com/products/products.cfm?familyID=108
avatar
Mudhen
Gold Member
Gold Member

Posts : 387
Join date : 2011-09-19

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Tue Nov 29, 2011 9:39 pm

Here is a exploded view picture of the drum valve. There is no indexing between the collar and the valve body.



avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Wed Nov 30, 2011 12:07 am

Here is a picture of the first carb body I made with the first mold attempt. You can see that the silicone picks up the fine details of the crack from the original carb body.



Inside detail of the threads and crack.



Here is a picture of the engine with the black carb body installed.

avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Wed Nov 30, 2011 8:30 pm

The below link has videos on making molds from parts.

http://www.freemansupply.com/video/masscasting/complex.htm


This is the basic process that was used to make the 2 piece mold with a parting line. I did not machine a recess in the wood but used clay. Speeds up the process a bit.

http://www.freemansupply.com/video/masscasting/complexqt500.htm

It is a long detailed process but worth it if no parts are available.

Jason
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Wed Jul 04, 2012 7:26 pm

Here it is in all its glory! Better than fireworks! Enjoy. 4th of July Flag Fireworks

avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  fit90 on Wed Jul 04, 2012 7:54 pm

Beautiful! Congratulations on the great job! Worth every second of the wait to see it running.

Enjoy it,

Bob
avatar
fit90
Diamond Member
Diamond Member

Posts : 1204
Join date : 2011-08-11
Location : Naples, Florida

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  microflitedude on Wed Jul 04, 2012 8:02 pm

Well done Jason.
avatar
microflitedude
Top Poster
Top Poster

Trusted Seller
I Support My Forum

Posts : 3417
Join date : 2011-08-17
Age : 20
Location : Columbia, SC

View user profile https://www.facebook.com/MiniCub?fref=ts

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Admin on Wed Jul 04, 2012 8:16 pm

That really is awesome! That is better than fireworks! I would guess that you are the first to start one of those Olympic rear drums in at least 30 if not 40 or more years! The molding job is great and it even worked great too!
4th of July Flag Fireworks

_________________
-Jacob


avatar
Admin
Administrator

Posts : 4646
Join date : 2010-07-27
Location : Roseville, Minnesota

View user profile http://sites.google.com/site/coxenginecollection/

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Wed Jul 04, 2012 8:44 pm

I have an HD video taken with my iPad but it is having problems loading to YouTube.

What do the Olympics normally do with an 8x4 APC prop? So far the valve body I made held up. It did soften up a little at the venturi threads. I have 2 runs on it and that will probably be it. Don't want to break the crank pin off!


Last edited by Jason_WI on Wed Jul 04, 2012 10:22 pm; edited 1 time in total
avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Jason_WI on Wed Jul 04, 2012 9:53 pm

HD video loaded up. This is the second run on SIG champion 25% with an all purpose cutter (APC) prop. The engine kicked back and cut the foam tip of my chicken stick off! Shocked

avatar
Jason_WI
Diamond Member
Diamond Member

I Support My Forum

Posts : 2259
Join date : 2011-10-09
Age : 43
Location : Neenah, WI

View user profile

Back to top Go down

Re: Cox Olympic Rear Drum Valve engine details. Now with Video!!!!

Post  Sponsored content


Sponsored content


Back to top Go down

Page 1 of 2 1, 2  Next

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum