4WD SRB Racer

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Huntit123
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Re: 4WD SRB Racer

Post by Huntit123 »

Hey, sorry, one last question. I know from your other post you bent it by hand. Did you use heat or not?

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Re: 4WD SRB Racer

Post by 1300GT »

No probs. All done without heat.
Chris.

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moj
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Re: 4WD SRB Racer

Post by moj »

awesome build,i think my build was based on the same magazine article you mention in your rear gearbox mods post tho youve taken it to a whole new level.
how did you fit the bearings in the front gearbox,are they shouldered? not about to try a four wheel drive myself but ide like to have a go at building a rear gearbox how did you figure out the spacing i had a look at my srb box awhile ago and coldnt really figure out how to accuratly measure the distande between centres of the three bearings

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Re: 4WD SRB Racer

Post by 1300GT »

Thanks very much. I read the article back in the eighties but for the life of me I can't remember which magazine it was in.

Yep the bearings are 5mm x 8mm flanged.

I took one side of an SRB gearbox and dropped one 5x11 bearing in the final drive gear bearing seat and another in the idler gear bearing seat. Then I took a measurement between the two bearings from the inner races of each bearing using vernier calipers. That gave me a measurement of 13.05mm. Added 5mm to the total for 18.05mm. The bearings are slightly loose in their seats so I added another .15mm to the total for 18.2mm.

I had a machine shop drill two 8mm holes in some steel bar 18.2mm between centres. This was used as a template to drill the holes in the G10 sheet. When the first front gearbox sideplates were finished and setup the backlash between gears was just right. At the time I didn't have the Buggy Champ diff in the gearbox, just the nylon final drive gear.
Later after installing the diff the backlash was almost gone and the gears didn't sound right when spinning them at speed. After measuring the outer diameter of the nylon gear and the brass diff gear I found out that the diff gear is slightly larger in diameter.

I made up a new template with the holes spaced 18.3mm between centres and the backlash is good with the second front gearbox.

If I had a milling machine it would be a lot easier. :lol:
Chris.

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moj
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Re: 4WD SRB Racer

Post by moj »

thanks for the informative and compehensive answer when i get a chance i will have a go at an srb box,from the quality of your work ide assumed you had a machine shop,even more impressed now

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Re: 4WD SRB Racer

Post by GoMachV »

Just for future reference, if you guys draw the parts in illustrator, AutoCAD, or just about any other digital format I can cut the material out of G10 for you for likely less than the machine shop cut your template :mrgreen:
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Re: 4WD SRB Racer

Post by 1300GT »

Thanks Jeff :D

Computer designing is something I'm going to start later this year.
Chris.

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Re: 4WD SRB Racer

Post by GoMachV »

It's addictive! Let us know if you need tips, there are a few of us that can help. I learned most of it on YouTube :mrgreen:
It's time to stand up to the bully. Support the companies that support the industry, not the ones that tear it down. Say no to Traxxas
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Re: 4WD SRB Racer

Post by Dadio »

I'm still dieing to see a video clip of the beauty running , any chance you could indulge us ?
If a jobs not worth doing then its certainly not worth doing well.
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Re: 4WD SRB Racer

Post by Dadio »

1300GT wrote: Wed Jan 18, 2017 6:55 pm Thanks very much. I read the article back in the eighties but for the life of me I can't remember which magazine it was in.

Yep the bearings are 5mm x 8mm flanged.

I took one side of an SRB gearbox and dropped one 5x11 bearing in the final drive gear bearing seat and another in the idler gear bearing seat. Then I took a measurement between the two bearings from the inner races of each bearing using vernier calipers. That gave me a measurement of 13.05mm. Added 5mm to the total for 18.05mm. The bearings are slightly loose in their seats so I added another .15mm to the total for 18.2mm.

I had a machine shop drill two 8mm holes in some steel bar 18.2mm between centres. This was used as a template to drill the holes in the G10 sheet. When the first front gearbox sideplates were finished and setup the backlash between gears was just right. At the time I didn't have the Buggy Champ diff in the gearbox, just the nylon final drive gear.
Later after installing the diff the backlash was almost gone and the gears didn't sound right when spinning them at speed. After measuring the outer diameter of the nylon gear and the brass diff gear I found out that the diff gear is slightly larger in diameter.

I made up a new template with the holes spaced 18.3mm between centres and the backlash is good with the second front gearbox.

If I had a milling machine it would be a lot easier. :lol:
Just for reference I thought I'd share the way i worked out the bearing spacing for my Scorpion front gearbox , it's less dependant on high accuracy of measurement .
First i took a piece of aluminium plate and drilled the 15mm hole for the diff bearing , then installed the diff with bearing , them placed the counter gear next to it with a piece of paper between like setting up a pinion gear , now my counter gear lay shaft has a 3mm hole drilled and tapped in the end of it so i found a small ball bearing that i could sit cupped in the lay shaft hole ,a gentle tap with the hammer on the end of the lay shaft made an impression in the alloy plate where the ball bearing was , this is the centre point to drill the lay shaft bearing hole .
When i fitted the bearing for the lay shaft i found I'd too much backlash so i simply saw cut 3/4 across the plate between the bearing holes allowing me to squeeze the bearing holes closer together by closing up the saw cut until i got the correct mesh , this was now my template for drilling the end plates .
If a jobs not worth doing then its certainly not worth doing well.
A problem shared is a problem halved but an advantage shared is no advantage at all.

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Re: 4WD SRB Racer

Post by 1300GT »

Thanks for the info about your gearbox. It's a neat way to do it.

The video will be a while yet. But, as soon as it's done it'll be here in this thread.
Chris.

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Re: 4WD SRB Racer

Post by adam lancia »

I'm gonna be that guy to dredge up an old thread. If there was ever a custom build thread that was worth dredging up, this is one of them...

I absolutely love this build! I was really hoping that by the time I got to the end of the thread, there would be a link to a video of it running :cry: :cry: I really appreciate your use of basic hand tools for the build, that gives me hope for a potential build I want to tackle this winter.

Awesome man, just awesome.

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Re: 4WD SRB Racer

Post by coxbros1 »

just saw it myself after u dredged it up...
quite possibly the best build ever done...ever!
Tap pic for clarity: Derek

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Re: 4WD SRB Racer

Post by 1300GT »

Thanks for the kind words fellas. I still don't have a camera that can record decent footage. Life seems to get in the way of RC plans sometimes. :D

There will be a video though. I think a lot of people would like to see it running.

Thanks again.
Chris.

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garfield88
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Re: 4WD SRB Racer

Post by garfield88 »

Fantastic job. I also want to convert the SRB to 4WD version but don't have the mechanic tools.... You can consider to launch this conversion pack to the market. I would definitely be your first batch customer :D

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