Whittle Aero V8

[cobra428]

Hi Guys,
Does anybody have any info on this engine? When I bought the kit from Hemingway they said the plans are correct. I found the Yahoo site with the V8 group. The errors I'm finding are this....Here they are talking about the distance from the center of the cyl to the lifter holes in the block (copied from yahoo)

"One issue that no one has mentioned before is that there is an error on the drawing of the crankcase top part. The distance from  the centre of the cylinders to the centre of the cam followers should be 0.39775” not 0.400”.  If you build to the 0.400” dimension then the followers will be 0.00225” out of alignment with the camshaft. (Assuming crank and cam gear centres are 0.5625&#148.  If you draw it up on the CAD this will be confirmed."

Can anybody tell me how to work to 5 decimal places? ???

I really would appreciate it if somebody out there knows something seriously wrong with this engine. Please let me know. Otherwise the build will begin in 2 weeks
Tony

 

[Mainer]

It sounds to me as though maybe somebody is too infatuated with their new CAD program to stop and figure out whether, functionally, that 2+ thou makes any practical difference in operation.

It might -- but it's also quite possible it's irrelevant. You'll have to evaluate from a functional point of view and decide.

 

[cobra428]

Thanks Mainer,
After I had posted, that same thought came to me too. I think all the errors are do to CAD modeling and not build machining. I'm thinking it's a virtual engine site! ;D
Tony

 

[Bluechip]

Tony ..

I don't know if it's of any relevance, but this engine had a series of articles in Model Engineer, starting April 1995, describing the build. By the designer ..

Bit beyond my capabilities, but to add to others posts, 1/100,000th Inch, .... ?? Nah, I'll leave that one alone ;D ;D

Just a thought

Dave

 

[Weldsol]

Yes CAD can confuse matters some of the time but is always handy for checking through before you lay cutting tool to material. Iv'e had the same problem when re-scaling the Shay on the CAD I ended up with some wierd dimensions that even the digital read out on the mill couldn't handle. I think that if you could manage to make the item then it would not fit other parts due to the tolerances.
Now we are talking about ambient temps, when machining parts to match others. What next positive pressure work shops to keep out any dust. :
I reset the dim, values on the CAD to only 3 decimal places (metric) and that stopped quite a lot of the strange figures

Paul

 

[kf2qd]

Sounds like someone who has little experience machining and much experience nit-picking. How big is the cam follower? how big is the cam? and will the couple thou make any difference in operation? Or - did the designer use 0.400 because it was easy to work with and plenty close enough for things to work.

Some folks have no understanding of tolerances. You make things "close enough" so that it can actually be biult without running the cost (in dollars for commercial, or excessive time for the hobbiest) to ridiculous levels. Make the parts to half a knat's eyelash for the critical parts, and work with a bit of space where it doesn't matter. And the product will last for years with little maintenance. (Like you car or motorcycle...)

 

[cobra428]

Hey Thanks Guys
You have given me a bit of confidence to start cutting metal. You know every time I have mention this engine to anyone (in the hobby of course) They said ooooohhhhh the plans are wrong that engine is messed up. The other side of me says how come this engine was a featured artical in ME Mag and won at the Brit's version of NAMES? So far I built 5 engines some from castings some from scratch and everyone of them needed a little TLC and common sense to get the fitting right, running and running right. That's what I think is so great about this hobby....you have to think and think about your next move and even the move after that! I'm a mechanical engineer and every time I have to put a tol. on a part of +.003 -.000 I think about how I can redesign so that I don't need such a crucial dim. and it can be mfg easier and cost effective.
So I'll come down off my soap box and get back to the shop and get my hit and miss finished so I can start the 8. I'm thinking I will start a build thread on the 8 after that.
Thanks and have a great holiday!
Tony

 

[mu38&Bg#]

The slight offset of the cam followers to the cam shaft will have an influence on valve motion and possible cam and or cam follower wear. That assumes one cam actually grind a cam perfect enough not to be the main source of error in the valve train. For an engine that is run for display this isn't an issue. The purists will have fits, but it won't stop the engine from running.

 

[RonGinger]

The other side of me says how come this engine was a featured artical in ME Mag and won at the Brit's version of NAMES?

Actually, he won a prize at NAMES as well. He brought the model over one year, about the same time it was in ME magazine. He had it on the Strictly IC table, which was right next to the main entrance door. On Sunday afternoon as most people were packing up he left it on that SIC table and someone grabbed it on the way out the door.

That really troubled a lot of people, and there was considerable publicity. Eventually the model was found and returned to the owner. It was never clear who grabbed it or how it was recovered.

As far as I know that was the only model ever stolen at a NAMES how.

 

[cobra428]

WOW!!
Never new that. That has got to be the most lowest thing! Especially coming from a fellow modeler! This engine to me is one of the most magnificent model engines (in my eyes) I ever saw. I hope to do it justice. G. Luhrs makes some great stuff on that scale too (if not smaller) but doesn't pub any plans. He is part ? of my metal club and I will visit his shop in a month or so. I plan to "grill" him over spark plug making and gearing of his stuff. He is amazing! In case you haven't seen his stuff go to.

http://www.minimodelengines.com/index2.htm

And be amazed
Tony

 

[Mo deller]

Looking forwards to seeing this build. Hope it goes well.
I looked at the Hemingway site and quite like the vee twin aero. Bit pricey for me at the moment though

Mo.

 

[GailInNM]

Tony,
I finally had time to get my notes out on the Whittle V8. (In another thread) When I said the cam drawings were wrong on the original drawing, I was working from memory. I should have looked things up first. I have two notes from others about the cam dimensions, but I have not checked the drawing out completely myself. I apologize for possibly passing on incorrect information.

I shared a table with Eric Whittle at NAMES in 1993 or 94. This was before the V8. He was displaying his Robin that year. During slow periods we had some time to chat. He is a good engineer and craftsman and I was impressed with both him and his models. The V8 uses a lot of the techniques that he developed when designing the Robin. I also saw him the year he had the V8 at NAMES, but about all we got to do was say hello.

I started on the V8 about 2-1/2 years ago, but had to put it on the shelf after a brief period because of health issues. Things are much better now. If you looked at the photos on the Yahoo site, you probably saw the crankcase and some other assorted parts in my folder. I have made some of the other small parts since then. I was planning on doing the camshaft next, but later changed my mind and made the fixtures to turn the crankshaft.

If you do decide to build the V8, I will follow with lots of interest. I am just finishing up some projects now and you have rekindled my interest in the Whittle. It is a beautiful engine. I might restart on it and build in parallel with you time wise.

Gail in NM,USA

 

[cobra428]

Hi GailinNM,
I searched on the yahoo site for "errors" "drawings". The only thing that popped up was the 5 place decimal thing on the lifter hole locations. Let me know is you turn up anything else. I'm studying the plans and the text, I still have to get my h&m running good but it's good "library" reading for now. He was using a "combo" lathe so, I'm try to work out some methods in my head for a separate mill and lathe method. Not to much different but different. Glad to hear you are gaining an interest back in the engine. Maybe we will inspire each other on to the finish! I'll take a look on yahoo for your stuff.
TonyR

 

[GailInNM]

Tony,
I don't know of any errors on the plans. There are a few places where roundoff errors could occur, but those are easy to catch as you go along. Besides, most of them will end up closer than the tolerances I work to anyway. I have a couple of sheets of things on the cams that others have made up, but at least one of them I think is BS. I think they read the drawing wrong, but unless I really sit down and check it out I don't really know. Also I am working with the original Model Engineer drawings and there may have been some changes made before the Hemingway plans were produced.

There are a few places that I had to do some searching on the drawings to work out some dimensions, but nothing that was wrong.

My crankcase has a few minor modifications to suit my working style, but the only thing functional is I changed the crankshaft bearings to imperial sizes so the crankshaft goes from 6mm to 1/4 inch. That was only because I have a big bag of new bearings that size. Of course other things associated with those changes have to be changed.

For the benefit of people following this thread that are not familiar with the Whittle V8, here is a photo of a completed engine from the Hemingway web site. Also, a link to the page on the site where the photo is in case someone wants more information.
http://www.hemingwaykits.com/acatalog/The_V8_Aero_Engine___Eric_Whittle.html

 

[cobra428]

Yeah GailinNM,
Those are the pictures that hypnotized me into buying the kit! I know I will probable change a few things myself. That sounds like a good change on the crank. I also saw a few things called out like a .307 hole reamed. That is an expensive reamer $100 and up. I just happen to have a .3125 in my tool box. Gee I think I'll live with a hole that's .0055 off of the drawing. and make it's mate .0055 bigger. Then mark up the dwg so I'll know what I did! Also I plan to go with 0,1 and 2 screws and stay away from the BA's!
TonyR

 

[GailInNM]

Tony,
I am changing all the fasteners to Unified also. Probably use socket head hex screws in most places. I know they don't fit the period of time, but I am not trying to build a scale model.
Gail in NM,USA

 

[stevehuckss396]

My crankcase has a few minor modifications to suit my working style

here is a photo of a completed engine from the Hemingway web site.

Where is the photo of your completed crankcase?

 

[GailInNM]

Steve,
I don't want to hijack Tony's thread, but I suppose that this will be OK as he is planning to start a new build thread when he gets started.
Here are front and rear views.
Gail in NM,USA

 

[cobra428]

Hi Gail NM
wow WoW WOW, don't worry about stealing my thunder, you've just given me the inspiration :bow:
I just need to get my coles h&m finished (see other thread by me in wip). I need to learn to take pic's though.
Tonyr

 

[steamer]

Damn Gail you do nice work! :bow: :bow: