Are Q40 Nelson and Jett motor mounting dimensions the same?

[turbine_guy]

Will a Nelson or Jett motor drop into the other brands motor mount and will the spinner backplate spacing to fuse be similar?

OR once the motor mounts been mounted/potted in the fuse-you’re stuck with running that brand motor?

I think that made sense(!)

[sahartman21]

The Jett and Nelson engines fit interchangeably in the mounts.

The Jett engine is lighter than the other. Therefore balancing will have to be done after making a change. The difference is from 1 to 2 ounces, depending on muffler and spinner options.

[airplanescotty]

The CG as Mr. Hartman stated is the critical path with regards to motor changes!!

Especially when one considers potential internal components relocations to re-establish CG without added weight!!

Scotty

[turbine_guy]

That’s great news,

I can compare performance with both brands in the airframes then!


Thank you!

Jake

[AlexVazquez]

The spinner backplate spacing to fuse is not as similar, for nelson you have 3 drive collet sizes to add space to the back plate/fuse gap but I'm not sure if you could do so for Jett.

[DHG]

Alex,

Are you sure you have the right drive collet? Nelson and Jett use slightly different thickness and taper. I've been using both brands of engine interchangeably (subject to minor CG adjustment as noted above), and unless the collet is wrong, the dimensions should be practically identical.

I would also note that Jett makes spinners that fit Nelson engines, so if you have one of those, check that you're using the collet that came with it.

Cheers,
Duane

[KRProton]

Here are images of my Too Sweet. I had originally installed the Nelson, but later installed a Jett. Only thing I had to change was slightly enlarging the cutout around the venturi for the Jett. But now that I look at the images, maybe I'm remembering that incorrectly. Looks like the cutout around the venturi of the Jett is too large, so maybe it's the Nelson that would need a larger opening for the venturi. Also, considerations for C.G. as previously mentioned for the weight difference between the two engines.

Oh yea, there may have been slight changes in the mufflers of each engine. I believe the angle on the Jett may have changed over time, maybe on the Nelson too, but I'm not sure about that. These are just minor changes.

Tim Lampe

[Jim DeYoung]

Just curious,
How much is weight difference between the two?
Thanks,
Jim

[DHG]

Jim,

Comparing the base engine & muffler only, I'm seeing the Jett heavier by 0.6 oz. Of course, the spinner may affect the total.

The Nelson has a larger bell on the venturi.

I don't always recheck the CG when I switch from one to the other, but I do always re-trim the airplane. It never takes more than about 2 clicks of elevator trim.

Cheers,
Duane

[Kurt Bozarth]

Alex,

Are you sure you have the right drive collet? Nelson and Jett use slightly different thickness and taper. I've been using both brands of engine interchangeably (subject to minor CG adjustment as noted above), and unless the collet is wrong, the dimensions should be practically identical.

Cheers,
Duane

Hey Duane,

I almost pulled my hair out (pulled Hank's out instead) wrestling with motor swaps between a Jett and two Nelsons. This was before I knew Mike made more than one collet size! One Nelson and the Jett would fit just fine with the right amount of space between the spinner backplate and the fuselage, but when I installed the 2nd Nelson, the spinner backplate rubbed...arghhhh!!!!!! After beating my wife, I discovered the Nelsons had different collets. Mike used to sell them in sets of three (three different thicknesses). I had a nice collection of collets until my tool box was stolen along with my truck en route to Wichita two years ago. Lonnie still owes me for that.

Love,
Anonymous

[GaryS]

Jim,

Comparing the base engine & muffler only, I'm seeing the Jett heavier by 0.6 oz. Of course, the spinner may affect the total.

IMG_2258[1].JPGIMG_2259[1].JPG

The Nelson has a larger bell on the venturi.

I don't always recheck the CG when I switch from one to the other, but I do always re-trim the airplane. It never takes more than about 2 clicks of elevator trim.

Cheers,
Duane

Now I'm confused. I've never used a Jett Q40 engine, but I've always heard they're lighter....but Duane's scale says otherwise. Does the weight difference change with elevation since Duane's a mile high?

[Greg Doe]

Based on where Duane lives, he might just be "high"?

[sahartman21]

Gary James and I compared the weight of his Jett with 2" spinner with my Nelson with Nelson Spinner. Gary's Jett was 1 ounce lighter.

Jett now has a lighter muffler that is available. If you have the new muffler this combo is about 1.75 ounces lighter.

[DHG]

Ohhhh, wait. That Nelson muffler is the one I emptied out to use as a bong. Never mind, mystery solved!

[AlexVazquez]

Alex,

Are you sure you have the right drive collet? Nelson and Jett use slightly different thickness and taper. I've been using both brands of engine interchangeably (subject to minor CG adjustment as noted above), and unless the collet is wrong, the dimensions should be practically identical.

I would also note that Jett makes spinners that fit Nelson engines, so if you have one of those, check that you're using the collet that came with it.

Cheers,
Duane

Hi Duane,
I'm using a 2" Jett spinner in my nelson engine, it is a very old model (not sure if now they are different) so, I do have to use the jett drive collet and I'm right on the go.

Yes, I've noted Nelson's drive collet has a different taper so I can't use them for the Jett spinner...

By the way, the back plate of my 2" Jett spinner has a little taper as well on the outside, it is not flat as nelson's spinner, some times I need to enlarge the hole in the fuselage to eliminate the inner rubbing.

cheers,
Alex