Author Topic: A Robinson from rejects.  (Read 35898 times)

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #30 on: September 21, 2017, 05:58:03 PM »
I would be very happy to look into the non starting issue.

There hasn't been an engine I haven't managed to get going, even the most stubborn.

The offers open.

Cheers Graham.

Offline Jo

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Re: A Robinson from rejects.
« Reply #31 on: September 21, 2017, 05:59:59 PM »

But that does mean 50% have been made to run, can't you work out whats wrong rather than waiting for someone else to tell you what it is?

Nick, I did have a bit of a go to get it running but when it drew blood I did not offer again. :ThumbsDown:

As I cannot move the thing on my own I have not bothered to do anything more with it. I have put it in a warm dry place to keep it safe.

I also have a rule that I do not try running engine on my own... it is all about safety. If it does go wrong then you need someone to either admister first Aid or to run you to the hospital. Surus is no good at that yet  :-\

Jo

« Last Edit: September 21, 2017, 07:23:01 PM by Jo »
Usus est optimum magister

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #32 on: September 21, 2017, 06:04:27 PM »
You could just pop the flywheels off then it could be carried to the workshop and the flywheels put back on.

I do that with all the big hit & miss engines - leave the flywheels loose as I bring the engine that I am working on in from the workshop and up stairs to my study at the end of the day - saves having anything getting nicked or going rusty.

J

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #33 on: September 21, 2017, 06:06:25 PM »
Quote
P.S. We all have engines that don't run, don't we Jason

But some of us have far more non running and unfinished engines than others, don't you Jo, I could list yours but would need to take my shoes and socks off :LittleDevil:

Offline Nick_G

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Re: A Robinson from rejects.
« Reply #34 on: September 21, 2017, 06:10:57 PM »
.
Suck-squish-bang-blow.  :ThumbsUp:

Or am I confusing engines with something I 'may' have read in the Kamasutra.?????  :D  :-[ ;) ;)

Nick

Offline b.lindsey

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Re: A Robinson from rejects.
« Reply #35 on: September 21, 2017, 08:05:47 PM »
Graham, I have been looking in on this project from time to time and find it a most interesting engine. Not to intrude on the positive comments made about the build so far and the useful information provided, but please folks, let's keep the personal stuff off thread. I know we all like to poke fun at each other and that goes for this side of the pond as well, but please....lets keep in mind that we have added over 100 members this month alone so far, many of them new to this hobby and forum, and we all need to continue upholding and promoting the friendly, welcoming,  and positive atmosphere that all of us as forum members have worked so hard to build and maintain. Sometimes it good to read a reply before hitting the send button in the context of how it might read to guests and especially new members. I have done the same so I am not guiltless either, but we all need to strive to keep MEM the best of the model engine forums.

Bill

Offline Vixen

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Re: A Robinson from rejects.
« Reply #36 on: September 21, 2017, 08:14:05 PM »
+1 behind Bill,

Lets keep it nice folks
It is the journey that matters, not the destination

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #37 on: September 21, 2017, 08:27:18 PM »
Ok. Back on topic.

The internal gear at first seemed to be a real obstacle.....

A little over an hours work in the foundry area.

Cheers Graham.

Offline crueby

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Re: A Robinson from rejects.
« Reply #38 on: September 21, 2017, 09:23:35 PM »
Ok. Back on topic.

The internal gear at first seemed to be a real obstacle.....

A little over an hours work in the foundry area.

Cheers Graham.
Those look great, but I got a bit lost on how you made the internal gears - did you use a normal outside gear as part of the mould? How was the master made if it started as an internal tooth gear?   :headscratch:

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #39 on: September 22, 2017, 11:43:10 AM »
Hello crueby.

The gears in the photograph are " in the rough " so to speak. I send them with the bulk that provided the pressure to form good tooth definition at the bottom of the die.

The die consists of 3 parts, the base ( first part ) that locates both outer ring ( second part ) and the tooth form ( third part ) in correct alignment to create the eccentric.

The base and ring both being made of Cast Iron. The tooth form was/is a standard 1.75 MOD spur gear attached to a shaft with a taper given to it above the gear. This taper makes it easier to remove it from the Zinc casting as it's cooling. I also carefully ground minute grooves under the gear to allow the trapped air to escape. This " sharpens " the edge of the casting.

I usually end up scrapping/re melting the first couple as the die seems to work better as the temperature increases, after that it's akin to " shelling peas " ... Melt, clean, pour, remove and repeat. You need really good quality foundry gloves though!

Cheers Graham.

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #40 on: September 22, 2017, 01:26:33 PM »
Mould shown on the top right of this photo, just pour in the metal and it forms around the offset gear and above it.



I may be wrong but a true internal gear should have a slightly different profile to just the negative image of a spur gear but for the loads and speeds this engine will see I doubt it makes any difference.

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #41 on: September 22, 2017, 02:40:20 PM »
Hello Jason.

Not wrong at all....

It's one of the reasons for the choice of a larger tooth form. And as you wrote the load is little more than compressing the spring of a ball point pen !!

Cheers Graham.


Offline crueby

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Re: A Robinson from rejects.
« Reply #42 on: September 22, 2017, 03:14:31 PM »
Slick setup, thanks for the explanation on the mould!

Offline Jo

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Re: A Robinson from rejects.
« Reply #43 on: October 03, 2017, 09:39:49 AM »
Hi Graham, I've been redrawing up the X Type drawings in Alibre..... There are a few what we term "features" in the drawings  ::)

Just finished drawing up the Ignition tube and Chimney but still not sure how it works  :headscratch:

Jo
Usus est optimum magister

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #44 on: October 03, 2017, 10:10:25 AM »
You will need to add a small burner to the 11mm hole Jo otherwise your hot tube will stay a cold tube. Apart from that it works like a hot tube, think of the tube like a glow plug, when it is heated by the burner stays hot just like a glow plug on an aero engine. Fuel/air mix when compressed in the cylinder and up into the hollow tube will ignite.