| Author | Message | ||
     Randy Roberson Prolific User Username: wascator Post Number: 193 Registered: 5-2009 |
Hi, I need one replacement waisted pushrod for SRH 9391. My dealer only sells the latest of the three different pushrods used in the pump over the years, and it requires purchase of the new-design lifter supports as well. What is going on? As the distance between the base circle of the cam lobe and the pump mount on the lifter cover is not changed, the only way I can see a different pushrod length is accommodated, is with a new lifter which will cause the pair to be equal in length to the original. Are they different diameters? Why can I not use the new lifter-pushrod together in my original supports? Are the waisted rods like I need still available anywhere? My good pushrod is 4 inches in length. I understand the issue of the lubrication failing in the original design; however mine seems to have functioned well for 44 years and I had rather spend the $700 asking price for the modified setup elsewhere on the Car, and I feel to better effect. | ||
| Randy Roberson Prolific User Username: wascator Post Number: 200 Registered: 5-2009 |
Update: In studying the parts literature so generously made available by our Hosts, I found one part number for the pump pushrods: UE 36857 and one lifter UE 36794, for the brake fluid Cars. Looks like the earlier part numbers were changed in favor of the modified parts which are recommended to be fitted. The parts lists do not list the original parts. I might be wrong. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1182 Registered: 6-2006 |
Randy, I'll see what I've got. I though I replied to this already? Does your pushrod get narrow and then get wide again? I'll measure what I have in used rods here. A modified set of used parts with used or new pattern pus rods will be a couple of hundred GB pounds. Regards, Paul. | ||
| Randy Roberson Prolific User Username: wascator Post Number: 201 Registered: 5-2009 |
Yes, SRH 9391 has the waisted pushrods. The broken one was badly corroded in the waisting. It has not had the modification; the pushrods are 4 inches long. Albers Bentley and Flying Spares have the modification parts, but do not offer any alternatives. I will do it if I can't find a pushrod. With The Boy and his university of choice getting all my money, I try to ecomomise! | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 377 Registered: 5-2012 |
I have what may be a silly question. Could this pushrod be turned on a lathe? Would anyone on the forum with a knowledge of metallurgy (David perhaps?) know what type of steel it is made from. How are the originals made? Are they extruded or machined. I am just curious if anyone has any ideas on the above question. Geoff | ||
| Randy Roberson Prolific User Username: wascator Post Number: 206 Registered: 5-2009 |
It had to have been made somehow: I figure it's probably SAE 4140. I don't know if it would require heat treatment to harden the ends. At any rate, Flying Spares have some 4 inch pushrods at 45 pounds plus 25 pounds shipping; they also have the used conversion kit, quoted at 150 pounds. I am checking if that is enough to do the job (i.e. both supports) or for 1, and I would need to buy 2. if I can do both for 150 quid, I might do it and get past it. | ||
| David Gore Moderator Username: david_gore Post Number: 1375 Registered: 4-2003 |
Hi Geoff, If I had been asked to specify an alloy steel for this application, it would have been SAE 6150 Chromium Vanadium steel with induction hardened faces [around 50 Rockwell C] on each end. I would not consider SAE 4140 as it does not have enough Carbon to give a suitable working hardness whilst maintaining sufficient impact resistance. As an aside and a great question for R-R Trivia Nights, what do Sir Henry Royce and Henry Ford have in common other than being key contributors to the development of the automobile? > > > > > > < < Answer: They both used heat treated Chromium Vanadium alloy steels for critical components which substantially improved both service life and safety. The reputation of Australian Sidchrome spanners was also due to the use of austempered SAE 6150 alloy steel which gave both hardness and toughness such that when belted with a hammer to "persuade" a recalcitrant bolt to release, the spanner would bend but not break unlike cheaper conventionally quenched and tempered spanners claimed to have been made from Chrome-Vanandium steel. SAE 6150 is one of my favourite alloy steels along with the BS970 EN25/EN26 Nickel-Chromium- Molybdenum alloys for critical applications requiring strength, ductility and abrasion resistance. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 378 Registered: 5-2012 |
David Thank you for your reply. It was a purely academic question. I was just curious if it would be possible to turn these parts in a lathe if they became unobtainable. I am assuming SAE 6150 Chromium Vanadium steel can be machined, in which case the answer appears to be yes. Geoff | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1183 Registered: 6-2006 |
I've checked through what I have here Randy and no pushrods that length I'm afraid. 4 inch pushrods at 45 pounds plus 25 pounds shipping; they also have the used conversion kit, quoted at 150 pounds. I am checking if that is enough to do the job (i.e. both supports) or for 1, and I would need to buy 2. if I can do both for 150 quid, I might do it and get past it. I'm sure that will be for one kit. As mentioned earlier I could do a pair of sets for a couple of hundred pounds. You could get away with replacing one set. Assuming that the good side is OK then that will mean less shimming etc. and less cost at the moment. Downside is that if the rod goes on the unmodified one in the future, you can not just swap the rod. (Although in theory you should shim to each push rod that is fitted) | ||
| Randy Roberson Prolific User Username: wascator Post Number: 209 Registered: 5-2009 |
Sorry to sow confusion: I remeasured my good waisted pushrod with a Starrett 4-5 inch micrometer: it is 4.483 inches long. Together with the lifter it is 4.630 inches long. Don't know how I got 4 inches before. | ||
| Nigel Johnson Prolific User Username: nigel_johnson Post Number: 122 Registered: 12-2008 |
I've had a little problem with pump pushrods with our 1980 Spirit ACH01253. The front one fractured right on the waisted part and crossed over itself. So i was unable to remove it without taking off the carbs and tappet chest cover. To cut a long story short I've just found the details of the pushrod lengths. The original was 4.336 inches or 110.11 mms pt no UE40331.I bought a new pair, they are for a Shadow 2 pt no UE36794, 4.36 inches long. 24 thou different. So the pump clearances had to be re-shimed, by 24 thou. Being a cutting forme maker I was able to make a cutter to cut various thicknesses of shim stock to enable me to adjust the pump clearances to within tolerance. 0.522" to 0.525". This is measured with a depth gauge micrometer placed on the top of the pump mounting boss to the top of the travel of the pushrod. I hope this is of some help. Regards, Nigel. | ||
| Randy Roberson Prolific User Username: wascator Post Number: 213 Registered: 5-2009 |
I have seen that some people drill into the top end of the pushrod and extract it; I presume they are able to fish the broken end out with a magnet. Mine were so gooked up with tarry oil residue that I would never have got them out. Good information here. For no more difference than that, I wonder why the engineers at Rolls-Royce did not just use the same pushrod? Were they discussing the trouble future hobbyists would have with all this during lunch, then breaking down with "evil genius" laughter? | ||
| Nigel Johnson Prolific User Username: nigel_johnson Post Number: 123 Registered: 12-2008 |
Sorry, I've just noticed my mistake.I should have written to the bottom of the travel of the pushrod. Bottom dead centre is the position for the measurement to be taken. Please accept my apologies, Nigel. |
