Gypsy 1/4” scale crankshaft material

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Gypsy 1/4” scale crankshaft material

This topic has 9 replies, 4 voices, and was last updated 30 October 2018 at 15:43 by Daggers.

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29 October 2018 at 12:36 #378214
Daggers
Participant
@daggers
Hi All,

Am new to this group, I have a question regarding crankshaft material.

Looking at the Gypsy crank and trying to decide on the best material and balance the machinability against the strength.

Can you experienced guys out give me your best guess as I have no experience in a crank of this size/use.
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29 October 2018 at 12:36 #2522
Daggers
Participant
@daggers
29 October 2018 at 16:42 #378243
JasonB
Moderator
@jasonb
EN8 on the drawings I have.
29 October 2018 at 16:57 #378244
mike T
Participant
@miket56243
I would go along with the choice of EN8 for the Gypsey crankshaft. It is a good compromise between strength and machinability. It is also readily available.
29 October 2018 at 17:24 #378249
Daggers
Participant
@daggers
En8 on order.

Am away from home at the moment so dont have the original drawings with me, did not realise steel spec was shown.

I have redrawn the crank on my laptop, which I have with me, as i found a drawing problem and needed to investigate before commiting to machining.

Does en8 need any stress reliving after rough machining and prior to finishing.
30 October 2018 at 06:51 #378290
JasonB
Moderator
@jasonb
Bright (cold rolled) will have more of a tendency to move than black (hot rolled) . What did you order and did you go for round or flat stock?

Edited By JasonB on 30/10/2018 07:40:15
30 October 2018 at 07:36 #378297
Ian S C
Participant
@iansc
Bright (Cold rolled) Will have a tendency to move, get hot rolled, the black stuff.

Ian S C
30 October 2018 at 08:47 #378304
Daggers
Participant
@daggers
Ordered round 21/4” diameter EN8M which i was told is the free machinng type of EN8. Not seen it yet but i presume it is bright bar.
30 October 2018 at 10:37 #378327
JasonB
Moderator
@jasonb
That's a lot of extra swarf when it would have come out of 50mm stock

When machining it flat I would take say 3mm off one side then flip it over and do 3mm off the other then back to the first for another 3mm and so on until you get down to thickness.

Then rough it out as shown on the drawing but a bit more than the 1.806 and leave for a couple of weeks. Then put in your ctr holes and machine.
30 October 2018 at 15:43 #378374
Daggers
Participant
@daggers
I agree, lots of extra swarf, but material came from a contact at cost who only had 21/4” round stock.

Would like to have purchased square/rectangular stock but i found it difficult to find supplier who would supply/ship small quanity at a reasonable price.

My first time working on an ic engine, had the plans/castings for years but other projects have got in the way.
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