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Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt


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14 hours ago, igor said:

One for the structural (and potentially other) engineers amongst us. My youngest has constructed a forge/foundry using a refractory cement consisting of a 50/50 mix of casting plaster and paving sand. We poured the thing on Monday evening. He is questioning how long he should allow it to cure before lighting a fire in it. I suggested 28 days as being the standard period for testing concrete samples. He's hoping to get away with a lot less. All advice gratefully accepted. 

Is it contained in a drum or something?

I had a look in some Shed mag articles about this but they don't say much. Give it a few days then start with a slow burn?

What's the worst that could happen?

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I need to put a new draw bar under out big tandem car transporter. (greenie which made an appearance at drag day a few years ago.) Due to cracks forming and it generally being a bit hodge podge. And made of c rather than box.

So my question is. What size box section should I make it from? Max weight combined it about 3t. 

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On 05/01/2022 at 16:06, RUNAMUCK said:

Does oil go off?

Just did an oil change on mums car yesterday. 

I reckon it must have been at least 5 years since it last had one. But I think last wof she'd only done 470kms. (During that year)

I know short trips is the worst thing for them. But does oil get too old?

The worst thing is very long periods sitting. Any sediment in the oil settles out so that when it's finally revived you damm near choke the intake - then the sediment gets pumped around the motor cos it opens any filter bypass.

As a favour to the wif I once recovered a Holden ute that had sat for 18months in a cop lockup. A girlfriend of hers wanted it to sell on behalf of the owner - in clink. Oil looked lovely on the dipstick. Pickup in Ashvegas. Halfway back to rown it started smoking....She sold it in the end.

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On 11/01/2022 at 16:23, igor said:

One week post pour. The plastic bucket is sacrificial formwork.

image.png.85bee7802fa718a7c13b6bce6b66a44e.png

 

Cut the bucket out and give it another week, The area around where the bucket is needs to be the driest but with it there it won't dry.

Start small with heat. Short heat periods with plenty of time to cool between. You're stressing it but trying not to break it.

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Thank you @GregT. What you say makes a lot of sense. Unfortunately the boy ran out of patience shortly after I took the above pics. He's using it right now. He lit a small fire in it first just to melt/burn the bucket enough to force the blow pipes through then gave it another day before going balls out twin hair dryer fan forced coal fired can melting. It's working quite well but there is some erosion of the face of the fire chamber and around the blow pipes. I suggested to him that he might like to clean it out and repair the eroded areas with a very stiff sand/plaster mix. Is this likely to be helpful in extending the life of the thing or is it a waste of effort? 

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Anyone know valve clearance for Honda g20 engine? 

Seems a bit too jdm to have any info online. Somewhere between 0.1 and 0.2 seems to be the vague answers for any Honda, weird I guess Honda owners just put farty exhausts on and call it done

Under hood stickers don't seem to have it, was Honda kind enough to cast it into the engine somewhere? 

I'm going to replace the cam tower Orings as there's oil coming into the spark tubes (along with replacing the actual plug seals) 

If not I guess I will measure them before and set it back to whatever makes sense

 

I'm saw somewhere the g20 was based on an f series engine with an extra jug on the end. But I can't find data for that either 

 

 

Might even be hydraulic 

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@JustHarry

I usually go with rectangular box section 3mm plus wall thickness.

I would avoid the riser you have to hold the hitch. I preferred a piece of 75x10 drilled and tapped with m10 threads and bolted with capped screws.

I also avoid welding across the top of the drawbar to the front of the trailer deck as I have been told it leads to cracking.

*how I have done them in the past.*

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38 minutes ago, Mof said:

Right thread? 

Axle stands, rating per stand or per pair?

Seems hard to find this info, most manufacturers seem to dodge the question 

AS/NZS 2538:2004 is per stand and I believe the default required

ASME is per pair.......

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3 hours ago, mopig said:

fuck me thats had some repairs!

how long is the unsupported section between the front crossmember seen there and the coupling? 

I typically use a 75x100x5 for this job, however that looks quite short, 4mm would suffice. 

It's not that far from the coupling to the front of the trailer. Maybe just over a meter.

 

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What does the OS hive-mind recommend for removing a shitload of tar from alloys/lower door sections that won't root the paint?  Road works crew went overboard on a couple of km yesterday, laying down a good 75mm of extra chip above the tarred surface which has left me with a few extra kg of wheel weights and the black shitty mess everywhere.

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