engine spacing

[builditright]

Can anyone tell me
what's the engine spacing (length and width)
for a rail mounted half-A engine?
 

[Randy Powell]

Walter,

You mean like for a TD or something? Distance between rails and length?

[Tim Wescott]

You mean like for a TD or something? Distance between rails and length?

If you do, it's gonna vary -- my Norvel 049 is 0.71 wide at the crankcase, while my McCoy 049 is 0.65.  I don't know what a Cox TD is, nor a Brodak 049.

[Bill Little]

Can anyone tell me
what's the engine spacing (length and width)
for a rail mounted half-A engine?
 

Hi Walter,

They all have different mounting dimensions.  The same brand usually are teh same, but Norvel to Cox (Medallion/TD) to Brodak do not match.

The Brodak .049 and .061 are in production along with the Wasps (.061 and .074), the
others are not in production, AFAIK.

The old McCoy/Testors/Wen Macs were different, too, as were the OK 1/2As.

Pick one, and we can give the spacing.

Mongo

[Wayne J. Buran]

Crankcase is 18MM wide, the screw hole spacing is 24MM from side to side is 24, and the hole spacing is 10MM is ctr to ctr.
Wayne

[builditright]

Okay here's what I need it for...

I have been given the approval to make Dick Sarpolus's designs, both R/C and C/L.
that said, I have started to put into AutoCAD a Half A profile Edge and I need the
measurements for the engine cutout.

See below.

[minnesotamodeler]

Set the mm beams 3/4" apart (inside edge to inside edge).  You may have to shave the inside corners off to clear the crankcase, but it makes for a snug fit, and the bolt holes will be nearer the center of the beams.

Don't even think about prefabbing the holes themselves, there's just too much variation.

[Tim Wescott]

Set the mm beams 3/4" apart (inside edge to inside edge).  You may have to shave the inside corners off to clear the crankcase, but it makes for a snug fit, and the bolt holes will be nearer the center of the beams.

Don't even think about prefabbing the holes themselves, there's just too much variation.

If I measured my Norvel correctly (which is questionable, I didn't take it out of the plane) then you're saying that a .71 case in a .75 space is "snug".  I'd say that's "loose".

My preference would be a kit that is cut out to put the bearers as close together as the narrowest engine you're likely to see, with instructions or kit features to widen them as necessary.  A close second would be to make them as wide as the widest reasonable engine, with a supply of shims to narrow them up.

But I'm kind of a finicky builder.

[George]

Walter,

I would go for .7 inches, or whatever Dick used for the Tee Dee. The TD and the Norvel  (and probably the Wasp) have the same mounting hole positions, although the crankcase on the Norvel is just a tad wider than the TD. Those should be, by far, the most used engines for that model.

I would make the hardwood mounts wide enough to accommodate a little whittling to fit other engines.

George

[builditright]

like this...  

.70 spacing
3/8"x1/4" mounts
with a norvel in it

[john e. holliday]

Do like Carl Goldberg used to do, if he doesn't have a patent.  The slots for the engine mounts were wider than needed and you shimmed them to fit the engine of choice.  At least that is what I had on all three of the profile stunters of his.

[minnesotamodeler]

You guys are right, I've been building off templates so long I forgot the measurements.  Checked one; I'm using 11/16" gap (.6875) which requires a little whittling of the inside edges.  Sorry for the misleading info.

[Steve Scott]

I've always found it's easier to cut a stick shorter than cut it longer.

Make the cutout narrower than required and we can trim it to get a good fit.

Those Brodak composite profile "C" mounts?  They are always too narrow.  I clamp mine in a 4" vise and file (a rasp works great to remove a lot of material; a metal file works great to hone it to the final size) to open it up one side at a time.   I file it flush with the vise jaws.  Works really well...