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020 TD Crankshaft Won't Fit Crankcase

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020 TD Crankshaft Won't Fit Crankcase

Post  ThermalSniffer on Tue Jun 02, 2015 5:18 am

Hi all,

Just bought a pair of new 020 tee dee crankcases from VGE on eBay. Not really necessary but my engine had lost a little anodising here and there on the crankcase over time and I wanted to make it look new again. Well the new ones arrived today so I duly dissassembled my 020 tee dee but on reassembling I found the crankshaft will not fit into either of the new crankcases.

Did the 020 tee dee crankshaft design change slightly at some point in production? My tee dee is an older model and I remember reading here when it transpired there are two kinds of pee wee crankshafts that differ with from one another dimensionally (knurled prop driver shaft diameter and the recessed portion on the crank varies in length). I wonder if a similar thing happened to the 020 tee dee.

Comparing the new crankcases to the original the major difference appears to be that there is anodising inside the nose of the crankcase where the crankshaft fits whereas the old crankcase has no anodising in there. That could be because it wore off on the old one but the fact remains I cannot fit the crankshaft I have into the new crankcases.

Thanks for any info,
Simon
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  TDbandit on Tue Jun 02, 2015 10:08 am

Could be the anodizing that's causing the interference. I've had that happen on other engines that I've had. Anodizing is a coating and while it's insignificant in most cases with the extremely close tolerances of the cox engine it can be an issue. (Bandit)
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  1/2A Nut on Tue Jun 02, 2015 2:31 pm

This is a tricky fix can you fit the crank in partial way? If so perhaps some lapping compound will remove the anodized surface well enough to do a slopppppy rich break in.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  TDbandit on Tue Jun 02, 2015 3:02 pm

Got to be careful with lapping compound since it will not only remove the anodizing but it can end up lapping the crank too. The anodizing probably only goes just inside the nose of the case but there should be no anodizing in the crank bushing if the crank goes in but binds you can take some fine steel wool and move it around the inside the case bushing testing the fit ever so often "the trick here is to just remove the anodizing" after you get a fit that doesn't bind, clean the case out thoroughly and then do like what 1/2A nut said and do an extremely rich break in run  to wear the case a little. (Bandit)
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  RknRusty on Tue Jun 02, 2015 3:16 pm

Something like toothpaste might be a safe way to try for safe lapping. Too bad, because that anodized crank tube makes a good bearing while it lasts.

Were these in a sealed Cox package?
Rusty

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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  Cribbs74 on Tue Jun 02, 2015 4:18 pm

I would be more inclined to chuck the crank in a drill and polish the crank to fit.

Once that anodizing is gone the case will wear out very quickly.

Crank polishing is pretty common among the speed crowd. The crankcase is anodized in it's entirety as the whole part was submerged during the process.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  dckrsn on Tue Jun 02, 2015 5:22 pm

I picked up one of VGE's .020 cases a couple of weeks ago.
I have a spare crank and I plan to build an engine around it .
Guess there's some polishing in my future. I didn't check the
fit till just now.
Bob
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  ThermalSniffer on Tue Jun 02, 2015 9:07 pm

This has been very informative, thank you guys. I will have to look into crank polishing and decide if it is worth it for me. I am still unclear how this situation has arisen. Either the cases did not normally leave the factory with anodise in the crank bushing or the cranks were made thinner at some point. My crank looks exactly like the one pictured above. The cases were not Cox bagged when they arrived. A small point but perhaps a clue unless VGE are simply stripping whole new engines to resell as parts.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  1/2A Nut on Wed Jun 03, 2015 8:29 am

You should send him a message on ebay and ask him why there is a fit issue and what his solution or awareness was there if worst case what reparations options are available.

I bought a TD .09 crank from him once it was a loose fit / if he is making parts quality control is in order.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  ThermalSniffer on Wed Jun 03, 2015 9:38 am

I have sent him a message about the issue. Thanks for the prompt.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  dinsdale on Wed Jun 03, 2015 8:06 pm

"Anodising" is a controlled layering of aluminium oxide onto an aluminium surface. In fact the AlO is formed on the surface by oxidising the surface of the parent aluminium.  AlO is also used extensively in industry as an abrasive.  (This subject came up in another thread recently.)  I would expect the anodised surface to be harder than the hardened steel crankshaft - as stated by others here.  Lapping with some toothpaste would be good, if the fit is no more than a millifart away from a clearance fit.  Most likely lapping that way would remove most material from the crankshaft, but would hopefully burnish the anodised surface too.  The abrasives found most commonly in modern toothpastes include hydrated silica, hydrated alumina (alumina/aluminium oxide/anodising - all the same thing), calcium carbonate, and dicalcium phosphates.  My understanding is that alumina is little use now, due mainly to it's abrasive ferocity.  However, toothpaste makes a very good ultra-fine lapping paste.  I agree with those warning not to remove the anodised surface from the crank journal, but a light burnish would be good - imo.  Personally I would be pleased to receive a new crankcase with a slight interference fit.  It would allow me to lap the case and shaft, ultimately giving me the longest possible life from the parts as well as the best performance.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  ThermalSniffer on Thu Jun 04, 2015 12:03 am

It's not possible to get the crankshaft through the bushing without damage. I haven't tried, of course, but get the impression I'd need to hammer the crankshaft through.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  Oldenginerod on Thu Jun 04, 2015 2:49 am

ThermalSniffer wrote:It's not possible to get the crankshaft through the bushing without damage. I haven't tried, of course, but get the impression I'd need to hammer the crankshaft through.
Definitely do not hammer the crankshaft through. affraid

Have you tried to insert the crankshaft from the front?  The crank should go in either way.  If you can insert it in the front of the case a little further, try to lap it that way first. There may be just a slight burr at the case end.

Anodizing is not just to colour the material, but as already stated, hardens the surface as well.  What many people don't realise is that even a Babe Bee crankcase is anodized without the use of dye.  The anodized surface is much more resistant to damage so by polishing the crankcase, as many do, you actually expose a softer surface which will be more easily marked and damaged in the future.

Rod.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  ThermalSniffer on Thu Jun 04, 2015 7:15 am

Reggie wrote back that these cases are original cox parts which he bought back in '95 or '96. He said he would soon check the fit himself with a crankshaft that he has.

Perhaps the specification changed at some point. It would be nice to have a late model 020 Tee Dee to compare to.

I will try the reverse fit that has been suggested above. It will give a clearer idea of where within the bushing the problem lies.
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Re: 020 TD Crankshaft Won't Fit Crankcase

Post  fredvon4 on Thu Jun 04, 2015 8:22 am

I also have bought a few items that were not proper sized*. I know that Cox mfg ran lots of parts as batches and as the tooling wore out some were looser or tighter than spec. On the assembly line as a worker inserted parts and found this particular condition, the suspect part(s)...in this case the crank or case... were checked. If the crank was over size it most likely went in a bin to be polished into spec. If the case was undersized, it most likely went into a reject bin as it was low cost and the effort to bring it into spec would not be cost efficient.

I suspect a barrel of this cases got sold as scrap

Still a good part... I would chuck a crank in a drill press or hand drill and polish it down to a close fit in the case then run in the engine as suggested several times above

*... some time back I bought 3 .049 TeeDee cases new in the package. When I went to assemble "made from parts" TeeDees, I found that two of the three cases were too long in the nose by some few thousands. A crank shaft with thrust washer installed would not turn. I checked each crank shaft and they were the same length and each worked fine in one of the 3 new cases... I checked each new case with the caliper and decided to remove a few thou from the nose knowing I would remove the anodizing where the thrust washer would ride....they are marked for never use electric ..... bottom line is I added three new TeeDee .049s into the total in service completely from internet parts


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