The Unofficial Mamod and Other Steam Forum

johnreid · Posted: Wed May 21, 2008 12:38 am Post subject: SE3 Jensen 15 shoot out

Upon some discussion via PM I decided to see how well a SE3 would operate a Jensen 15.
My SE3 is Esbit fired, so I guess that I will have try this again once I get my Meths burner.
This is how I went about the test.
I loaded the Esbit burner with 5 Esbit tablets, I filled the boiler with boiling water, draining a bit out once it started to drip out of the overflow. This water was heated to the point that it was still bubbling when in the boiler. I then screwed in the Overflow Plug and the Safety Valve, lit the Esbit and placed the tray under the boiler.
On real cool thin about the SE3 is it likes to take off on its own, it almost immediately started to run real slow. The Jensen 15 was probably turning 30 RPM at the most. There was enough resistance that the Safety Valve was popping and the water running down th side of the boiler extinguished the Esbit.
I quickly removed the wet Esbit, wiped things dry and placed anothe 5 Esbit under the boiler. Again the SE3 ran slow and the water from the Safety Valve extinguished the Esbit.
I then removed the 15 and hooked up my Jensen 100. 5 new Esbit and the thing ran like there was no tomorrow, real high RPMs and the Safety Valve did not pop.
Then to test the 15, I ran it with my Jensen 25 Hobby grade and had 4 minutes of bright light, after that the engine ran , but the 15 slowed it enough that it wasnt turning the 15 fast enough.
One observation, the piston surface area of a Jensen 25 is more than double that of the SE3s pistons.
Conclusion, the SE3 wont run the Jensen 15. It still is one of the most fun engines to operate and I think it is truly the flagship of the Mamod
SE line.
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IndianaRog · Posted: Wed May 21, 2008 1:54 am Post subject:

John, I found pretty much the same thing when I converted an SE3 to a wood base. I first mounted one of those Austrian generators like Mr. O has on the SE3 base to power a Jensen lamp post. The drag of that generator simply killed the SE3...nothing.

I then took a small DC motor I had snagged from a defunct printer, tried spinning it with a Dremel and found it did a good job of powering a lamp at not too many rpms AND had little drag. That was then incorporated into a bit of sink drain tubing and some fabricated bits of brass for a holder and it works like a charm.

A simpler way of doing what I did would be to find one of the Meccano black plastic housed generators that Jensen used to put on their 15E generator (for lighter wt. engines). Mooseman kindly gifted me one of those and it is the DC motor on my 51R. I later picked up a spare on UK eBay for $4 and another 3 or 4 for shipping. It will remain my spare in the even Moose's ever quits. BUT, try searching Meccano motor on US and/or UK eBay...they come up regularly and make dandy generators for very little money...AND will work fine with an SE3 or similar sized engine.

Rog
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flywheel61 · Posted: Wed May 21, 2008 2:19 am Post subject:

Rog, John kindly did the test for me, as I bought that 1952 blue-cast iron based 15# and haven't been able to get it to work with my SE3 family.

I guess I'll have to to try again for a 10/25 in good condition and hope Gil and pennyanneboats don't see it, fat chance of that,

.

Cheers

Chris
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Mamod mania strikes again

Mister Occlusion · Posted: Wed May 21, 2008 2:22 am Post subject:

A fellow on youtube has stuck a pulley to a computer muffin fan and is using that for a generator on a Jensen 75... Not something I had considered trying myself.

I suspect the Jensen 15 is capable of some impressive output if only it could be wound fast enough. I blew a standard bulb in one once by flipping it over with several turns of dental floss on the pulley (by hand).

SE3 will run a stepper fine. Just at a lower output due to the gearing. Has no problem lugging it, though.
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steamyman · Posted: Wed May 21, 2008 8:22 am Post subject:

Don't mean to ruin your thread, John, but I've had the #15 light a bulb with a SR1 as the steam power. though to do this, I needed to put upgraded SV on the SR1 boiler.

Atticman · Posted: Wed May 21, 2008 8:40 am Post subject:

Guess thats why Mamods didnt do a generator version till the SP range/ showmans,
the fly on the SP is large and the generator is small.

Great experiment John

I am sure the the cylinder size is the right reason,
the fly is pretty light too so the combination allows real speed but less power.

Dads German engines are quite the opposite,
slow chuggers that work generators with ease

flywheel61 · Posted: Wed May 21, 2008 9:57 am Post subject:

That probably explains why the 15# was shown in the item pics running off a German engine,

http://cgi.ebay.com.au/ws/eBayISA...sPageName=STRK:MEWN:IT&ih=024

Cheers

Chris
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Mamod mania strikes again

johnreid · Posted: Wed May 21, 2008 11:06 am Post subject: